Patent Application
20220096317
Disclosed embodiments are related to haptic actuators for transmitting heat and/or mechanical vibrations to an adjacent surface.
Wearable technology has become of great interest, enabled by the shrinking of sophisticated microelectronics, maturation of wireless communication, and increasing energy density of various battery chemistries. However, wearable technology to date has focused primarily on sensing and data collection. Haptic actuation (i.e., the generation of sensations related to the sense of touch including both tactile and thermal sensations) has been increasingly recognized as an impactful area for wearable and mobile technology.
In one embodiment, a haptic actuator for transmitting heat and mechanical vibrations to an adjacent surface includes a heating membrane, one or more supports constructed and arranged to transmit mechanical vibrations to the heating membrane, and a body. An actuator is disposed in the body, and the actuator is constructed and arranged to apply mechanical vibrations to the one or more supports. The one or more supports physically separate and support the heating membrane relative to the body.
In another embodiment, a method for transmitting heat and mechanical vibrations to an adjacent surface includes heating the adjacent surface with a heating membrane and applying mechanical vibrations to one or more supports mechanically coupled to the heating membrane to transmit the mechanical vibrations to the adjacent surface.
In yet another embodiment, a haptic actuator for transmitting heat to an adjacent surface includes a body, a heating membrane, and one or more supports constructed and arranged to thermally isolate the heating membrane from the body. The heating membrane has a heat capacity per unit area between or equal to one of 0.002 J/(K·cm2) and 0.2 J/(K·cm2).
It should be appreciated that the foregoing concepts, and additional concepts discussed below, may be arranged in any suitable combination, as the present disclosure is not limited in this respect. Further, other advantages and novel features of the present disclosure will become apparent from the following detailed description of various non-limiting embodiments when considered in conjunction with the accompanying figures.
The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component that is illustrated in various figures may be represented by a like numeral. For purposes of clarity, not every component may be labeled in every drawing. In the drawings:
Conventional wearable technology for temperature control faces an array of technical challenges that limit or prevent the use of thermotactile actuation in current mobile and wearable technology. One such limitation is that wearable technology is most often powered by a wearable battery, which may significantly restrict power and energy available for operation of a haptic actuator. Despite this limitation conventional approaches to generating sensations of warmth are power intensive, and state-of-the-art solutions use large batteries or include a direct connection to an external power supply. Another limitation is that haptic actuation is typically done using close contact with the skin. Accordingly, typical actuators might provide temperature and vibrotactile sensations in different locations using separate actuators which may present packaging and size problems. Another technical challenge is that the effectiveness of a haptic actuation may depend largely on the location(s) of application as well as the control of the actuator which may affect how the subjective sensation is perceived by a user. Finally, making a wearable technology sufficiently lightweight and robust to be comfortably worn on the body in a range of environments may present additional packaging challenges.
To help aid implementation of a haptic actuator in various mobile applications, the Inventors have recognized that it may be desirable to provide a low weight and/or low-power system. Specifically, and without wishing to be bound by theory, the Inventors have recognized that heat capacity and thermal mass of a haptic actuator influences the power and energy used to heat an adjacent surface according to a desired temperature profile. That is, a haptic actuator with a higher heat capacity (i.e. thermal mass) may use more energy to heat an adjacent surface to a particular temperature than a haptic actuator with a lower heat capacity. Thus, a lower heat capacity of a haptic actuator may show reduced power consumption due to the corresponding lower amount of power used to heat the device when heating an adjacent surface according to a desired temperature.
In view of the above, the Inventors have recognized the benefits of a haptic actuator which includes a thermally isolated heating membrane (i.e., thermotactile actuator) that is at least partially thermally isolated from a body of the haptic actuator. More specifically, the Inventors have recognized the benefits of a low heat capacity heating membrane that is supported and at least partially thermally isolated from a body so that the thermal mass of the heated portion of the system remains low. Maintaining a relatively low thermal mass for the heating portion of a system may provide a relatively high efficiency heating of an adjacent surface with rapid response times. In one such embodiment, one or more supports may extend between a body of a haptic actuator and a heating membrane to support the heating membrane relative to the underlying body. These one or more supports may either be made from a thermally insulating material and/or have sufficiently thin cross sections such that the heating membrane is at least partially thermally isolated from a body of the haptic actuator.
In some embodiments, it may be desirable to apply heat and vibration at the same location. In such an embodiment, a haptic actuator may be constructed and arranged to apply a combination of haptic sensations, such as thermal sensations and vibrotactile sensations to an associated surface. For example, a heating membrane of a haptic actuator may be coupled to an actuator constructed to apply mechanical vibrations using the above noted one or more supports. The one or more supports may be directly or indirectly coupled to the actuator to transmit the applied mechanical vibrations. For example, the supports may extend out from an actuator supported within the body of a haptic actuator and/or the supports may extend out from a portion of the body connected to an actuator such that mechanical vibrations are transmitted from the actuator to the supports through the body. In either case, the one or more supports may also be constructed to be sufficiently rigid to support the heating membrane while transmitting vibrations from the vibrotactile actuator without permanently deforming. Thus, vibrations may be transmitted from the vibrotactile actuator through the supports to the heating membrane for applying vibrations to a surface adjacent the heating membrane. Such an arrangement may beneficially reduce the size of a haptic actuator while providing both thermal and vibrotactile stimulation to a surface while also maintaining a relatively high thermal efficiency for the system. Similar to the above, the heating membrane may still be at least partially thermally isolated from the actuator and an associated body of the haptic actuator. Accordingly, the haptic actuator may apply vibrations to an adjacent surface while maintaining a relatively low effective thermal mass for the heating membrane which may enable both rapid temperature changes as well as low power operation of the haptic actuator. Such an arrangement may also decrease an overall size of the system since the actuator and heating membrane may be aligned in some configurations.
As noted above, in some embodiments, a haptic actuator may include one or more supports that extend between a heating membrane and an associated actuator and/or other appropriate portion of a haptic actuator body. The supports may maintain the heating membrane in a spaced configuration relative to the actuator and/or haptic actuator body to at least partially thermally isolate the heating membrane. In some embodiments, the one or more supports may also create an air gap between the heating membrane and the body. The thermal isolation of the heating membrane may either be provided by a reduced surface area of the heating membrane being in contact with the supports and/or the supports being made at least partially from an insulating material and/or including an insulating material disposed between the heating membrane and the supports.
It should also be understood that the one or more supports may take any appropriate form that may be used to physically separate and thermally isolate the heating membrane from the body and/or actuator of a system, including, but not limited to, ribs, annular rings, fins, and columns. These structures may also have any appropriate shape including linear and curved arrangements as might occur with linear spaced apart ribs that extend between the heating membrane and a portion of the body of a system. The membrane supports may be arranged based on the desired level of thermal isolation and/or a desired amount and direction of flexibility of a heating membrane for ergonomic skin contact at a particular location. For example, additional flexibility in a middle portion of a membrane may be provided by supports located at an edge of the membrane.
In some embodiments, a haptic actuator may include a heating membrane with one or more heating elements disposed in the heating membrane. For example, the heating elements may be resistive heating elements corresponding to conductive material through which a current may be passed. The conductive material may then be resistively heated by the current to generate heat therein that is then conducted to an adjacent surface. The heating elements may be disposed in an electrically insulating layer of material such as a layer of dielectric material. Appropriate types of dielectric materials may include, but are not limited to polyimide, rubber, thermally conductive plastics, and silicone. In some embodiments, as noted above, the membrane may have a low heat capacity so that a reduced amount of energy may be used to heat the heating membrane itself during application of a desired temperature profile to a surface. In one such embodiment, a heating membrane may have a sufficiently small heat capacity such that a majority of the heat generated by the heating elements may be conducted to an adjacent surface in contact with the heating membrane instead of being used to heat the membrane itself and/or a body of the haptic actuator. Accordingly, the heating membrane may have a high efficiency when used to apply heat to an adjacent surface, as less wasted energy is used heating the membrane and haptic actuator.
While the current disclosure is primarily directed to the use of resistive heating elements, embodiments in which other types of heating elements are used including, for example, thermoelectric materials are also contemplated as the disclosure is not limited in this fashion.
It should be understood that the actuators disclosed herein to apply mechanical vibrations to an associated heating membrane of a haptic actuator may correspond to any appropriate type of actuator. For example, piezoelectric actuators, electrical solenoids, rotary motors with offset masses attached to an output shaft, linear resonant actuators, eccentric rotating mass vibration motors, and/or any other appropriate type of actuator capable of applying a mechanical vibration to a system may be used.
As used herein, the term “haptic” may refer to sensations relating to the sensation of touch which may include, but is not limited to, temperature sensations, vibrational sensations, pressure sensations, and textural sensations. Accordingly, a haptic actuator for applying haptic sensations to an adjacent surface (e.g., skin of a user) may provide one or more sensations relating to touch to the adjacent surface. For example, a haptic actuator may apply both thermotactile (i.e. temperature variations) and vibrotactile sensations (i.e. vibration and/or pressure changes) as well as any other appropriate type of sensation related to the sensation of touch, as the present disclosure is not so limited.
In some embodiments, it may be desirable to separately control a temperature applied to different regions of an adjacent surface. In such an embodiment, a heating membrane of a haptic actuator may incorporate a plurality of independently-operable heating elements and/or groups of heating elements, which may be referred to as thermal pixels. That is, the independently-operable heating elements may be used to selectively apply heat to different regions (i.e., thermal pixels) of an adjacent surface. For example, the heating elements may be arranged into separate elements and/or regions to form the thermal pixels which may allow independent temperature control of different portions of an adjacent surface. In some embodiments, the thermal pixels may be arranged in linear or planar arrays within a heating membrane to form a grid of thermal pixels. Of course, the thermal pixels may be arranged in any suitable pattern or relative position to one another, as the present disclosure is not so limited. The thermal pixels may be actuated individually, in selected groups, or all at once depending on the desired thermal sensation. For example, a plurality of independent thermal pixels may be actuated sequentially to apply heat to the skin of a wearer of a haptic actuator to simulate a warming sensation traveling across the skin of a user.
In some embodiments, a heating membrane of a haptic actuator may include one or more physiological sensors which may obtain information about a user. In one such embodiment, a sensor window may be formed in a heating membrane to permit a sensor aligned with and/or disposed in the sensor window to sense one or more physiological parameters of the user. For example, a sensor may be aligned with a hole and/or transparent portion of the heating membrane. Appropriate types of sensors that may be included in such an embodiment may include, but are not limited to, temperature, heat flux, galvanic skin response, heart rate, and blood oxygen saturation (SPO2) sensors. The information from these sensor(s) may be used to control one or more aspects of a haptic actuator based on feedback from the adjacent surface and/or the haptic actuator itself. The sensed physiological parameters may be used to determine a user state which may correspond to either a physiological and/or emotional state of the user. For example, physiological information may be used to determine stress levels, anxiety levels, temperature comfort level, exertion levels, the occurrence of particular conditions such as hot flashes, and any other appropriate type of physiological and/or emotional state of a user. In some instances, the user state(s) may then be used to modify control of the haptic actuator. For example, when it is determined that a user is experiencing high anxiety levels, the haptic actuator may be controlled to apply a calming sensation such as a slow rhythmic tactile sensation and/or a warming sensation to a wearer.
To help enable the accurate control of a temperature profile applied to a surface, in some embodiments, a haptic actuator may include one or more temperature sensors in thermal contact with a heating membrane. In some embodiments, the one or more temperature sensors may be integrated into, and/or may be thermally connected to, the one or more supports which are in thermal contact with the membrane. Alternatively, the temperature sensor may be in direct contact with the heating membrane as the disclosure is not so limited. A temperature signal provided by the one or more temperature sensors to an associated control of the haptic actuator may be used to enable a closed-loop control of the heating membrane, though other types of control schemes may also be used. Without wishing to be bound by theory, due to the relatively low effective heat capacity of the disclosed heating membranes and systems, small changes in skin temperature may be rapidly reflected in the temperature of the heating membrane. Therefore, the temperature of the heating membrane may be substantially equal to a temperature of the surface adjacent to the heating membrane when the heating membrane is not being heated. Thus, the temperature sensor may be used to monitor both the temperature of the heating membrane during operation and a skin temperature of a user when the heating membrane is not actively being heated.
In some embodiments, a heating membrane may include at least one thermal fuse and/or at least one heat flux sensor to further refine control of a heating membrane. The thermal fuse may be use to limit the temperature of the heating membrane during one or more operating states to provide a desired amount of thermal sensation during different situations. For example, if a wearer of the heating membrane was in a hot environment or hot from exertion such that a temperature of the heating membrane is greater than or equal to a threshold temperature, the heating membrane may be disabled from applying heat to the wearer. A heat flux sensor may be similarly used to determine cutoff points or limits for operation the heating membrane. For example, the heat flux sensor may be used to limit heat output to an adjacent surface to be less than or equal to a threshold heat flux. Alternatively, the heat flux sensor may be used to measure heat flux from the adjacent surface, and activate or deactivate the heating membrane based on the sensed heat flux. For example, a hot surface may have a positive heat flux from the adjacent surface (e.g., an overheated wearer) to the heating membrane. According to this example, a measured positive heat flux to the heating membrane may be used by an associated controller to deactivate the heating membrane.
Various operating and design parameters for a haptic actuator for controlling both thermal and vibration sensations applied to a user are detailed below. It should be understood that the various parameters may be used in any appropriate combination to provide the desired operating characteristics of a particular haptic actuator. However, should be understood that while particular values are given parameters both greater than and less than those noted above are also contemplated as the disclosures not so limited.
While a haptic actuator may apply sensations to any appropriate size area, in one embodiment, the surface area of a heating membrane may be greater than or equal to 0.1 cm2, 0.5 cm2, 1 cm2, 5 cm2, 10 cm2, 25 cm2, 50 cm2, and/or any other appropriate surface area. Correspondingly, the surface area may be less than or equal to 100 cm2, 80 cm2, 60 cm2, 30 cm2, 15 cm2, 7.5 cm2, 2 cm2, 0.75 cm2, 0.2 cm2, and/or any other appropriate surface area. Combinations of the above noted ranges are contemplated, including, but not limited to, surface areas between or equal to 0.1 cm2 and 5 cm2, 5 cm2 and 15 cm2, 15 cm2 and 75 cm2, 75 cm2 and 100 cm2, as well as 0.1 cm2 and 100 cm2. Of course, different combinations of the above described surface area ranges are also contemplated as well as surface areas greater than and less than those noted above as the present disclosure is not so limited.
Another design parameter relevant to haptic actuators with thermal pixels is the density of heating circuits per unit area. The density of thermal pixels may determine the spatial resolution for temperature profiles applied to a user. Further, without wishing to be bound by theory, thermal sensitivity varies widely across the body based on the density of warm thermoreceptors on the skin. The density of warm thermoreceptors on the body is typically between 0.3 and 1 thermoreceptors per cm2. Accordingly, haptic actuators intended for use with different portions of a body may include different numbers of thermal pixels. For example, a haptic actuator positioned in a location with sparse thermoreceptors may have larger heating elements to generate equivalent subjective thermotactile sensations with lower spatial resolution. In contrast, a haptic actuator positioned in a location with dense thermoreceptors may have smaller, closely positioned heating elements to generate thermotactile sensations with higher spatial resolution. In one embodiment, the density of independent heating elements may be greater than or equal to 0.005 pixels/cm2, 0.01 pixels/cm2, 0.05 pixels/cm2, 0.1 pixels/cm2, 0.25 pixels/cm2, 0.5 pixels/cm2, 1 pixels/cm2, and/or any other appropriate heating element density. Correspondingly, the independent heating elements be less than or equal to 1.5 pixels/cm2, 0.75 pixels/cm2, 0.3 pixels/cm2, 0.15 pixels/cm2, 0.075 pixels/cm2, 0.02 pixels/cm2, 0.0075 pixels/cm2, and/or any other appropriate heating element density. Combinations of the above noted ranges are contemplated, including, but not limited to, heating element densities between or equal to 0.005 pixels/cm2 and 1.5 pixels/cm2, 0.1 pixels/cm2 and 0.5 pixels/cm2, 0.25 pixels/cm2 and 1 pixels/cm2, as well as 0.01 pixels/cm2 and 1 pixels/cm2. Of course, different combinations of the above described heating element density ranges as well as ranges both greater and less than those noted above are also contemplated as the present disclosure is not so limited.
In some embodiments, a total thickness of the heating membrane may be suitably thin so that there is limited thermal mass added by the membrane itself. Accordingly, a heating membrane may have a total thickness greater than or equal to 0.05 mm, 0.1 mm, 0.15 mm, 0.2 mm, 0.25 mm, 0.3 mm, 0.4 mm, and/or any other appropriate thickness. Correspondingly, the heating membrane may have a total thickness less than or equal to 0.5 mm, 0.35 mm, 0.25 mm, 0.20 mm, 0.175 mm, 0.125 mm, 0.075 mm, and/or any other appropriate thickness. Combinations of these thicknesses are contemplated including, for example, a thickness between or equal to 0.05 mm and 0.5 mm, 0.15 mm and 0.25 mm, 0.1 mm and 0.4 mm, as well as 0.1 mm and 0.3 mm. Of course it should be understood that other possible combinations of the above noted ranges, as well as ranges both greater than and less than those noted above, are also contemplated.
In some embodiments, the thickness of the heating membrane is much smaller relative to the transverse surface area which is used to contact an adjacent surface and conduct heat. Accordingly, such a heating membrane may have suitably low thermal mass (i.e. heat capacity) to be used efficiently for wearable haptic actuators. Of course, any suitable dimensions for the heating membrane may be employed as the present disclosure is not so limited. Several parameters useful for evaluating this performance are provided in detail below.
The one or more supports associated with a heating membrane may have any appropriate combination of dimensions to provide a desired amount of support and thermal isolation for a particular haptic actuator. However, in one embodiment the surface area of the supports in contact with a heating membrane may be a percentage of a surface area of the heating membrane which is less than or equal to 90%, 75%, 50%, 25%, 10%, 5%, 1%, and/or any other appropriate percentage of the heating membrane surface area. Correspondingly, the surface area of the supports in contact with the heating membrane may be a percentage of the surface area of the heating membrane which is greater than or equal to 1%, 3%, 10%, 15%, 30%, 60%, 75%, and/or any other appropriate percentage of the heating membrane surface area. Combinations of these ranges are contemplated including, for example, a surface area of the supports in contact with the heating membrane may have an area that is equal to a percentage of the surface area of the heating membrane that is between or equal to 15% and 50%, 5% and 30%, as well as 15% and 75%. Of course different combinations of the above ranges, as well as ranges both greater and smaller than those noted above, are also contemplated.
In some embodiments, it is desirable that a heating membrane is thermally isolated from a body of the haptic actuator and has a low heat capacity to provide low power thermal control. Without wishing to be bound by theory, if the heating membrane has poor thermal isolation or moderate heat capacity then generating dynamic temperature profiles may use significantly more power than is desirable in a wearable device. The role of thermal isolation and heat capacity may heavily influence haptic actuator performance and may be used to guide the design of thermal properties of a heating membrane. Without wishing to be bound by theory, one parameter for quantifying thermal efficiency of the haptic actuator may be a thermal coefficient of performance (COP), which may be defined as a ratio of the amount of heat conducted into an adjacent surface and the amount of power used by the heating membrane. A COP of 1 means the same amount of heat was delivered to the adjacent surface as power was provided to the haptic actuator, whereas a COP of 0.5 implies that half of the power delivered to the heating membrane was not applied to the adjacent surface. Thermal dissipation from a heating circuit is not directional and any conductive or convective channels for heat flow may reduce the COP of the membrane. For example, heat flow through the supports to an associated body of a haptic actuator would reduce the coefficient of performance. In this context, the measured COP of the device is a measure of the degree of thermal isolation of the membrane. Accordingly, increasing the thermal isolation of the membrane may increase the COP, thereby improving the effectiveness and efficiency of the haptic actuator.
In some embodiments, a haptic actuator may be controlled to apply a temperature profile to an adjacent surface. As discussed previously, poor thermal isolation directly increases power consumption to generate a given temperature profile, but there are also secondary effects to consider in the context of a temperature profile. In some embodiments, a temperature profile includes a thermostasis (i.e., cooling) period after a warmth (i.e., heating) period during which the thermal system is allowed to equilibrate and return to a desired temperature. Without wishing to be bound by theory, the lower the COP (i.e., the poorer the thermal isolation) the more energy is used to generate a temperature profile. That is, if a heating membrane is not thermally isolated or insulated from the rest of the system, the temperature of the entire system may be raised to achieve a particular temperature of the heating membrane. Correspondingly, more heat and energy input into the system results in more heat in the system that is dissipated during the thermostasis period. More specifically, as more heat is input into the system, the body or other structures of the haptic actuator may absorb the excess heat which is then dissipated during the thermostasis period to return the heating membrane and overall system to a desired temperature. Accordingly, reduced thermal isolation between a heating membrane and body of haptic actuator may result in decreased coefficients of performance and a longer thermostasis period between warmth periods.
In view of the above, a thermal coefficient of performance (COP) defined as the ratio between heat transferred to an adjacent surface and the power consumed to heat a heating membrane of the haptic actuator may be greater than or equal to 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, and/or any other appropriate COP. Correspondingly the COP may be less than or equal to, 1, 0.95, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, and/or any other appropriate COP. Combinations of the above noted ranges are contemplated, including, but not limited to, COPs between or equal to 0.3 and 1. Of course, different combinations of the above described COPs as well as COPs different than those noted above are also contemplated as the present disclosure is not so limited.
Another design parameter relevant to haptic actuators is a heat capacity per unit area of the heating membrane. The heat capacity per unit area may be suitably low such that the heating membrane may rapidly and efficiently apply heat to an adjacent surface without using excessive energy to heat the heating membrane itself. In one embodiment, the heat capacity per unit of a heating membrane may be greater than or equal to 0.001 J/(K·cm2), 0.004 J/(K·cm2), 0.01 J/(K·cm2), 0.05 J/(K·cm2), 0.075 J/(K·cm2), 0.1 J/(K·cm2), 0.125 J/(K·cm2), 0.15 J/(K·cm2), 0.3 J/(K·cm2) and/or any other appropriate heat capacity per unit area. Correspondingly, the heat capacity per unit area of the heating membrane may be less than or equal to 0.5 J/(K·cm2), 0.2 J/(K·cm2), 0.14 J/(K·cm2), 0.11 J/(K·cm2), 0.09 J/(K·cm2), 0.07 J/(K·cm2), 0.04 J/(K·cm2), 0.009 J/(K·cm2), 0.003 J/(K·cm2), and/or any other appropriate heat capacity per unit area. Combinations of the above noted ranges are contemplated, including, but not limited to, a heat capacity per unit area between or equal to 0.001 J/(K·cm2) and 0.5 J/(K·cm2), 0.01 J/(K·cm2) and 0.05 J/(K·cm2), as well as 0.075 J/(K·cm2) and 0.5 J/(K·cm2). Of course, different combinations of the above described heat capacity per unit area, as well as heat capacities per unit area both larger and smaller than those noted above, are also contemplated as the present disclosure is not so limited.
Without wishing to be bound by theory, a person's perception of temperature is a complex interaction of both absolute temperature, temperature difference relative to current skin temperature, and a rate of change of the temperature applied to the person's skin. Accordingly, when applying a temperature profile to a user that is intended to apply a thermal sensation, the applied temperature profile may include temperatures and rates of temperature change as detailed below. In one embodiment, the temperature may be greater than or equal to 20° C., 25° C., 30° C., 31° C., 35° C. and/or any other appropriate temperature. Correspondingly, the applied temperature may be less than or equal to 45° C., 40° C., 36° C., 35° C., 33° C., and/or any other appropriate temperature. Combinations of the above noted ranges are contemplated including, for example, temperatures applied to a user that are between or equal to 20° C. and 45° C., 20° C. and 40° C., 30° C. and 36° C., as well as 31° C. and 35° C., with a temperature of 36° C. being preferable in some embodiments. These temperature ranges may be combined with rates of temperature change applied to a user's skin that are greater than or equal to 0.01° C./s (Celsius per second), 0.05° C./s, 0.1° C./s, 0.2° C./s, 0.5° C./s, 1° C./s, 1.5° C./s, and/or any other appropriate rate of temperature change. Applied rates of temperature change may also be less than or equal to 2.0° C./s, 1.75° C./s, 1.25° C./s, 0.75° C./s, 0.3° C./s, 0.15° C./s, 0.075° C./s, and/or any other appropriate rate of temperature change. Combinations of these rates of temperature change are contemplated including, for example, a rate of temperature change between or equal to 0.01° C./s and 2.0° C./s, 0.05° C./s and 1° C./s, 0.1° C./s and 0.3° C./s, 0.01° C./s and 0.1° C./s, as well as 0.5° C./s and 2° C./s. Of course, different combinations of the above described temperature ranges and rates of temperature change, as well as ranges both greater than and less than those noted above, are also contemplated as the present disclosure is not so limited.
A passive cooling rate of a haptic actuator may be important for control and effectiveness of applying temperature profiles in quick succession while also avoiding thermal adaptation of a user. That is, the passive cooling rate of a heating membrane of the thermotactile actual may determine how often a temperature profile may be applied to the adjacent surface. As noted above, it may be desirable to allow a heating membrane of a haptic actuator to cool passively in an unpowered state to reduce the amount of power consumed by the haptic actuator during operation. In one embodiment, the heating membrane and associated supports disposed between the heating membrane and an associated portion of a haptic actuator body may be constructed appropriately such that the heating membrane cools with a desired rate of temperature change toward an initial temperature of the adjacent surface. For example, in cases where the adjacent surface is skin, the heating membrane and associated supports may cool from a temperature around 40° C. to a skin temperature between about 30° C. and 34° C. In another embodiment, the heating membrane and associated supports may cool from a temperature around 40° C. to a temperature between approximately 34° C. and 36° C. which may correspond to an upper limit for generation of a thermoneutral sensation for a user. In another embodiment, the heating membrane and associated supports may cool from a temperature around 40° C. to a temperature between 25° C. and 36° C., 30° C. and 36° C., and/or any other appropriate temperature range depending on the particular application. Of course, the heating membrane and associated supports may cool to any appropriate temperature based at least partly on the temperature of the adjacent surface, environmental conditions, and the applied temperature profile, as the present disclosure is not so limited. Additionally, embodiments in which the heating membranes do not cool to a particular temperature range are also contemplated as the disclosure is not limited in this fashion.
In some embodiments, the heating membrane and associated supports disposed between the heating membrane and an associated portion of a haptic actuator body may cool with a desired rate of temperature change toward the initial adjacent surface temperature under standard atmospheric conditions in an unpowered state. Standard atmospheric conditions may correspond to 1 atmosphere and 20° C. Under such conditions, the rate of temperature change may be a negative temperature change with a rate greater than or equal to 0.1° C./s, 0.25° C./s, 0.5° C./s, 0.75° C./s, 1° C./s, 1.5° C./s, 2° C./s, and/or any other appropriate cooling rate. Correspondingly, the rate of temperature change may be less than or equal to 2.5° C./s, 2.0° C./s, 1.75° C./s, 1.25° C./s, 0.9° C./s, 0.6° C./s, 0.4° C./s, 0.15° C./s, and/or any other appropriate cooling rate. Combinations of these rates of temperature change are contemplated including, for example, a rate of temperature change between or equal to 0.1° C./s and 2.0° C./s as well as 0.5° C./s and 2° C./s. Of course, different combinations of the above described temperature rates, as well as rates of temperature change both greater and less than those noted above, are also contemplated as the present disclosure is not so limited. In some embodiments, the above noted rates may occur when the heating membrane equilibrates towards a temperature between about 30° C. and 36° C. and/or any other appropriate range of temperatures as noted above.
The above noted temperature changes may be applied cyclically to a user. Accordingly, in some embodiments, the individual warmth and thermostasis (i.e. cooling) portions of a temperature profile may be applied for various durations. For example, the individual portions of a temperature profile may be applied for durations greater than or equal to 1 second, 2 seconds, 5 seconds, 15 seconds, 30 seconds, 1 minute, 2 minutes, 5 minutes, and/or any other appropriate time period. Correspondingly, the individual portions of temperature profile may be applied for durations less than or equal to 10 minutes, 5 minutes, 2 minutes, 1 minute, 30 seconds, 15 seconds, 5 seconds, 3 seconds and/or any other appropriate duration. Combinations of the above ranges are contemplated including, for example, durations for the individual thermal periods that are between or equal to 2 seconds and 15 seconds, 1 second and 5 seconds, 30 seconds and 2 minutes, 30 seconds and 10 minutes, and/or any other appropriate combination. Of course embodiments in which durations both greater than and less than those noted above are applied by a haptic actuator are also contemplated as the disclosure is not so limited.
The above noted rates of temperature change, as well as other rates of temperature change described herein, may either refer to an average rate of temperature change during a particular portion of a temperature profile when changing from a first temperature to a second temperature and/or they may refer to a temperature change rate that is applied during at least a portion of the applied temperature profile. For example, variable or constant temperature change rates may be applied when changing from a first temperature to a second temperature. Therefore, a particular rate may either be applied during at least a portion of the noted temperature change and/or the rate may correspond to an average rate during the noted temperature change.
In some embodiments, a haptic actuator and thermotactile control system provide energy-efficient generation of warming sensations in wearable form-factors using a low amount of power. Accordingly, when a haptic actuator applies a desired temperature profile to an adjacent surface, the haptic actuator may consume power during a warming portion of the thermal profile as detailed below. In one embodiment, the power consumed by thermotactile actuation during a warming portion of a temperature profile may be greater than or equal to 0.05 W, 0.1 W, 0.25 W, 0.5 W, 1 W, 2 W, 4 W, and/or are other appropriate power consumption. Correspondingly, the power consumed by thermotactile actuation may be less than or equal to 15 W, 10 W, 5 W, 3 W, 1 W, 0.75 W, 0.5 W, and/or any other appropriate power consumption. Combinations of the above noted ranges are contemplated including, for example, power consumption that is between or equal to 0.1 W and 1 W, 1 W and 5 W, 1 W and 10 W, as well as 1 W and 5 W with a power consumption of 5 W or less being preferable in some embodiments. Of course, any suitable amount of power may be consumed by a haptic actuator, including power rates both greater than and less than those noted above, as the present disclosure is not so limited.
In some embodiments, a haptic actuator may apply vibrations to an adjacent surface according to a particular vibrational profile. Without wishing to be bound by theory, particular vibrational patterns, frequencies, or amplitudes may be associated with a particular sensation or a wearer of the haptic actuator. Accordingly, the haptic actuator may vary the vibration applied to the adjacent surface using variations in amplitude, frequency, and/or pattern. For example, the actuator may apply mechanical vibrations to the adjacent surface using multiple pulses that may either be constant and/or may vary in regards to magnitude, frequency, and/or pulse rate. Of course, the vibration pulses may be applied in any suitable pattern, frequency, or amplitude, as the present disclosure is not so limited.
The haptic actuator may apply mechanical vibrations in a particular frequency range, which in some embodiments may be inaudible. In one embodiment, vibrations may be applied to an adjacent surface at a frequency greater than or equal to 1 Hz, 5 Hz, 10 Hz, 50 Hz, 100 Hz, 150 Hz, 200 Hz, 250 Hz, and/or any other appropriate frequency. Correspondingly, the vibrations may be applied at a frequency less than or equal to 300 Hz, 225 Hz, 175 Hz, 125 Hz, 75 Hz, 25 Hz, 7.5 Hz, 2.5 Hz, and/or any other suitable frequencies. Combinations of these frequencies are contemplated, including, for example, vibrational frequencies between or equal to 10 Hz and 200 Hz, 100 Hz and 200 Hz, 20 Hz and 350 Hz, as well as 1 Hz and 350 Hz. Of course, different combinations, as well as frequencies both greater than and less than those noted above, are also contemplated as the present disclosure is not so limited.
The haptic actuators may apply mechanical vibrations at a particular pulse rate which may correspond to a physiological parameter (e.g., heart rate) or other predetermined value. In one embodiment, the mechanical vibrations may be pulsed at a rate greater than or equal to 30 pulses/min, 40 pulses/min, 50 pulses/min, 60 pulses/min, 70 pulses/min, 80 pulses/min, and/or any other appropriate pulse rate. Correspondingly, the mechanical vibrations may be pulsed at a rate less than or equal to 120 pulses/min, 100 pulses/min, 85 pulses/min, 75 pulses/min, 65 pulses/min, 55 pulses/min, 45 pulses/min, and/or any other appropriate pulse rate. Combinations of these pulse rates are contemplated, including, for example, pulse rates between or equal to 30 pulses/min and 120 pulses/min, 40 pulses/min and 85 pulses/min, 50 pulses/min and 70 pulses/min, as well as 50 and 60 pulses/min. Of course, different combinations of the above described pulse rates, as well as pulse rates both greater and less in those noted above, are also contemplated as the present disclosure is not so limited.
In some embodiments, a haptic actuator and associated controller may be suitable for integration with other wearable technologies, other forms of sensory actuation, and/or with larger more complex systems through wired and/or wireless communication. In some embodiments the haptic actuator may be incorporated into a wearable article (e.g., an article of clothing). For example, in certain embodiments, a haptic actuator as described herein may be incorporated in a scarf, necklace, armband, wristband, hat, shirt, vest, pants, leggings, sleeves, headphones, ear buds, eyeglasses, goggles, or any other suitable wearable article capable of being worn on any appropriate portion of a person's body. The size of the haptic actuator may be selected, in some embodiments, such that the device fits comfortably on or around a wrist, an ankle, a head, a neck, a torso, an arm, a leg, a calf, an ear, a face and/or any other appropriate portion of a person's body. Additionally, embodiments in which a haptic actuator is not incorporated into a wearable article are also contemplated. For example, a haptic actuator may configured such that it may be applied manually by a person and/or may be incorporated into a separate stationary system. Accordingly, it should be understood that the currently disclosed haptic actuators are not limited to any particular form factor and/or size.
There are numerous applications for haptic actuators according to embodiments disclosed herein. Several non-limiting examples are provided below.
In some embodiments, a haptic actuator may be used to influence an affective state of a wearer. Without wishing to be bound by theory, it has been previously demonstrated that thermotactile actuation may be used to influence a person's affective state by leveraging psychophysiological associations between sensory experiences and emotional states. For example, warmth and vibration are both used to facilitate muscle relaxation. As another example, warmth may be applied to help a wearer cope with loneliness. Temperature profiles may also be applied to influence other affective states, such as applying fast heat pulses for energizing a wearer, slow heat pulses based on heart beat to calm a wearer, etc. In addition to thermal sensations, vibrotactile sensations can be used to calm or excite the wearer depending on the precise rhythm and pulse profiles used. Sensations of warmth may also influence the experience of social emotions (e.g., empathy, pride, loneliness, embarrassment, etc.).
In some embodiments, the independent heating elements may be used to relay information to a wearer of the haptic actuator through targeted temperature manipulation. For example, heating pulses from one heating element may be used to relay physiological information, provide haptic feedback for games or entertainment, or relay any other information useful to the wearer. Each heating element may be associated with a particular type of information, such that a message relayed by temperature profile is clear to a wearer. For example, a haptic actuator integrated with another wearable device may be used to provide notifications, alerts, and/or navigational cues that are inconspicuous and do not visually or aurally distract the user. Another application may be enhancing media with complementary haptic sensations for a more immersive or engaging experience for gaming or other entertainment. For example, a haptic actuator may be used to generating a more immersive gaming experience by adding haptic sensations that complement activity in the game.
In another possible application, a haptic actuator may measure a physiological state of a user and may provide biofeedback cues to the user based on the measured information to help guide the user into a desired physiological state. For example, the haptic actuator may provide feedback to a wearer to guide the wearer into a relaxation state (i.e., meditation).
In another embodiment, a wearable haptic actuator may be used to provide warmth for people with thermal discomfort. According to this embodiment, sensors monitoring the physiological state of a user may be used to predictively operate the actuators, providing the desired level of warmth when the environment changes. The haptic actuator may also incorporate physiological information that may indicate a wearer is uncomfortable and apply heat to the wearer in response.
In yet another embodiment, a controller of a haptic actuator may be designed to accept a wide range of potential inputs or cues for driving thermotactile actuation. The haptic actuator can be built into an external system that provides inputs or may be in wireless communication with other connected systems. For example, exemplary external systems may include as smartphones, personal computers, media equipment, physiological sensing systems, and other wearable technology (e.g., headphones, virtual reality goggles, augmented reality glasses, smart clothing, etc.). These systems may influence or modify control of the haptic actuator. For example, playing media through headphones may cause a cooperating haptic actuator to apply haptic sensations such as thermal and/or vibrotactile sensations to a wearer that are synced with the media. Thus, the haptic actuator may cooperate with any connected systems to supplement and/or enhance those system's features and/or operation.
Another example of a connected system may be a physiological sensing system on a wearer or on another person. The sensing system may be used to evaluate a psychophysiological condition of an individual which may be correlated with temperature profiles applied to the user. This can be applied as biofeedback by the haptic actuator, in which variations in the temperature profiles applied to the user may be correlated with an individual's state of relaxation or excitement. Physiologically-informed haptic actuation can also be used to convey an affective state of the user. This information may either be logged internally, output to a separate remotely located server, and/or communicated to a wirelessly and/or wire connected device. For instance, in some embodiments, a first haptic actuator may communicate a detected user state which may correspond to a physiological and or psychological state of the user to a second haptic actuator. The second haptic actuator may communicate the sensed state to a user of the second haptic actuator using either thermal and/or vibrotactile sensations. For example, a haptic actuator may convey to a wearer when a user of a connected haptic actuator is experiencing a particular affective state. Thermal and/or vibrotactile sensations may also be used to directly modulate the experience of emotions that warmth and slow tactile sensations have been shown to mitigate, such as feelings of loneliness or anxiety.
In another embodiment, a system either wirelessly or physically connected to a haptic actuator may be a smartphone which may cooperate with the haptic actuator to provide thermotactile cues to a user. Without wishing to be bound by theory, thermotactile cues may be a more inconspicuous form of notification than existing solutions that rely on visual, audio, or vibrotactile cues. Wearable haptic actuators may be paired with a smartphone or other computing device to provide temperature profiles based on the particular type of notification from the smart phone. For example, a haptic actuator may provide specific temperature profiles for notifications related to messaging, alarms, and/or navigational cues. Of course, a haptic actuator may provide any suitable haptic sensation to a wearer to provide a notification of a wearer of a desired event on connected computing device.
Turning again to entertainment systems such as a television, game console, or virtual reality system, a haptic actuator may be used to increase the engagement of a user experiencing various forms of media such as movies, television, video games, commercials, and/or music. In some embodiments, the media may be pre-encoded with haptic cues (e.g., temperature and/or vibration profiles) that are sent to the controller of a haptic actuator. These haptic cues may then be used to apply thermal and/or vibration sensations to a user. In other embodiments, the controller may process the media and generate temperature and/or vibration profiles that may be applied to a user by the haptic actuator. In embodiments in which a haptic actuator is used with a video game, the haptic actuator may be integrated into a hand held controller for the video game. Similarly, in some embodiments, haptic actuators may be placed in multiple locations across the body or integrated into a virtual reality headset to provide additional sensory inputs that can be used to create more immersive virtual reality experiences. For example, thermotactile actuation may be used to convey when the user is in a hot environment or interacting with a hot object in virtual reality. As another example, thermotactile actuation may be used to convey sensations relating to social interactions in virtual reality, such as social touch.
Turning to the figures, specific non-limiting embodiments are described in further detail. It should be understood that the various systems, components, features, and methods described relative to these embodiments may be used either individually and/or in any desired combination as the disclosure is not limited to only the specific embodiments described herein.
The heating membrane 110 may also include one or more resistive heating elements 112 disposed in a dielectric layer 114. In some embodiments, the dielectric may be a polyimide film (e.g., Kapton). Of course, the dielectric may be any suitable material with a suitably low heat capacity and electrical conductivity, as the present disclosure is not so limited. The resistive heating elements 112 may be formed of a conductive material and is arranged to generate heat when electric current is applied to the conductive material. As shown in
According to the embodiment shown in
In some embodiments, it may be desirable to provide a robust electrical connection to a heating membrane if it is to apply vibrotactile sensations to a surface. That is, in some cases, it may be desirable to ensure an electrical connection to a vibrating membrane so that electrical connectivity is not lost over repeated vibrational cycles. To provide a robust electrical connection, in one embodiment, a support 120 such as that shown in
To further reduce the amount of heat transferred to a body 102 through the associated supports 120, in some embodiments, the one or more supports 120 may the at least partially made from an insulating material. In one such environment, as depicted in
According to the embodiment shown in
In view of the above arrangements and variations, it should be understood that the supports may have any number of different arrangements and/or shapes. Accordingly, even though particular shapes such as circles, squares, line, and pin supports have been shown in the above embodiments, other appropriate types of shapes and arrangements contemplated as the disclosures not so limited. For example, other appropriate types of shapes for supports may include, but are not limited to, arcs, ovals, rectangles, triangles, stars, pentagons, hexagons, and/or any other appropriate shape and combination of shapes. Additionally, while individual isolated heating elements have been depicted in the figures, should be understood that each of the depicted heating elements may correspond to an array of heating elements and/or pixels as the disclosure is not limited in this fashion.
In some embodiments, the information measured by the above noted sensor may be used to at least partially control operation of a haptic actuator. For example, in one specific embodiment, a sensor may be used to monitor a heart rate of a user. Since an elevated heart rate may be indicative of stress, a controller of a haptic actuator may cause the haptic actuator to apply calming slow pulses of vibrotactile feedback to a wearer in response to a detected heart rate above a threshold heart rate to influence the affective state of a wearer.
In some embodiments, conductive pads 136 may be disposed on an exterior surface of the heating membrane such that the conductive pads may be placed in contact with the adjacent surface while the heating membrane conducts heat to the adjacent surface. The conductive pads may be used to measure galvanic skin response, apply electrical stimuli, and/or perform any other desirable function. In some embodiments, additional sensors or devices may be integrated into the heating membrane to gather information about the adjacent surface or otherwise perform a desirable function on the adjacent surface as the disclosure is not limited in this fashion.
As noted above, in some embodiments, the conductive pads 136 may be used to measure galvanic skin response (GSR). Without wishing to be bound by theory, GSR is a measurement of electrodermal activity which is a useful physiological signal of stress levels. GSR typically uses precise measurement of the conductivity of the skin through multiple contact points. The contact points may be integrated into the membrane 110 as exposed conductive pads on the surface such that they make contact with the skin of a wearer when being worn. GSR may be used to control the haptic actuator. For example, if a high stress level is sensed using GSR, such as a GSR signal greater than a threshold signal, the haptic actuator may apply a soothing temperature profile and/or vibrotactile actuation to influence the affective state of the wearer.
In another embodiment, the conductive pads 136 may be used to provide electrostimulation to the skin of a wearer. The electrostimulation may be localized based on the position of the conductive pads to generate a particular haptic sensation for the wearer. Electrostimulation can be used for a range of established therapeutic applications, including pain relief and behavior change. Electrostimulation may also be applied as a haptic actuator for media and entertainment purposes. Electrostimulation may be applied to an adjacent surface in combination or independent of thermal actuation and vibrotactile actuation to create any desirable haptic sensation.
In some embodiments, the membrane architecture of
While several embodiments in which different numbers and arrangements of heating elements, i.e. thermal pixels are depicted in the figures and described above, the current disclosure is meant to encompass any number of different heating elements and arrangements. For example, a heating membrane may include an array of heating elements arranged in rows and columns in any number of different shapes. Accordingly, the current disclosure should not be limited to only the heating membranes shown in the figures.
The actuator 104 may be sized and shaped to be disposed within a cavity 140a formed in the housing 140. The contacts 116 and associated leads may extend through an electrical passage through 140b formed in the housing such that the leads may be connected to an appropriate power source and/or controller. Thus, the assembled haptic actuator may include a heating membrane 110 supported above the surface of the actuator. In some embodiments, the edges of the heating membrane may overlay at least a portion of the housing exterior around a periphery of the cavity in which the actuator is disposed. This may help to support the edges of the heating membrane. As above, the support may be constructed to have sufficient stiffness to also transmit vibrations generated by the actuator to the heating membrane so that the vibrations may be transmitted to an adjacent surface in contact with the heating membrane. Also, similar to the prior described embodiments, the above construction may help to physically separate and creates an air gap between the heating membrane and the actuator as well as the housing. As the contact area between the heating membrane and support, as well as the contact area between the edges of the heating membrane and the housing, is significantly less than a surface area of the heating membrane itself, the heating membrane may be thermally isolated from both the actuator and housing of the haptic actuator. Accordingly, an effective thermal mass of the haptic actuator 100 may be reduced during operation as compared to more typical systems while also providing vibrotactile stimulation to a surface the heating membrane is in contact with.
The actuator, heating membrane, support, and housing may be connected to each other in any appropriate fashion. For example, appropriate attachment methods may include the use of adhesives, mechanically interlocking components, fasteners, and/or any other suitable method for connecting the one or more components of the system. Additionally while the components have been depicted as separate assembled components, embodiments in which one or more components are integrally formed with one another are also contemplated.
While specific examples of heating membrane constructions are provided above, should be understood that the current disclosure is not limited to any particular construction and/or method of forming a heating membrane.
Having described a possible temperature profile generically above, a specific controller for implementing such a control method is described below in regards to
where TOFFSET is a predetermined temperature above the temperature of the adjacent surface TSurface. The target temperature profiles can operate using absolute temperatures (i.e., using TOffset) or may be defined relative to the initial temperature of the surface (i.e., using ΔTOffset). As shown in
As shown in
A specific system for implementing the above noted control is shown in
Without wishing to be bound by theory, the controller and process shown in
Table 3 details one embodiment for a parameter space for operating a haptic actuator with a controller according to embodiments described herein:
According to some embodiments, a heating membrane may be in a warmth period until it reaches a predetermined temperature according to a desired temperature profile FN(t). Similarly, the heating membrane may remain in a cooling period until it reaches a predetermine temperature. In some embodiments, the heating membrane may be heated during the warmth period until it reaches a temperature between 35-40° C. which may provide a warming sensation to the skin of the wearer without feeling hot. In some embodiments, the heating membrane may be allowed to cool during the thermostasis period until the heating membrane reaches a temperature between 30-34° C. Without wishing to be bound by theory, cooling to this temperature range may be sufficient to overcome thermal adaptation of a wearer to the elevated temperatures applied during a warming period. In some embodiments, the cooling period (i.e., thermostasis period) may be longer than the warmth period as it is a passive rather than an active process. However, embodiments in which a duration of the applied warmth periods are shorter than or equal to a duration of the applied cooling periods are also contemplated as the disclosure is not limited in this fashion.
In some embodiments, a control process for operating a wearable haptic actuator with a heating membrane may include receiving feedback information from one or more sensors disposed on the haptic actuator. For example, the control process may include receiving power information, voltage information, heat flux information, and/or any other suitable information for feedback control. According to embodiments incorporating power information and/or voltage information, a temperature sensor may be omitted from the wearable haptic actuator. That is, the haptic actuator may apply a temperature profile (e.g., FN(t) in 19A) to an adjacent surface by applying a power and/or voltage profile without receiving feedback temperature information in some embodiments. Such an arrangement may be beneficial to improve the simplicity of the wearable haptic actuator and provide feedback control without a separate temperature sensor. Of course, any suitable sensors in any suitable quantity may be employed to control the haptic actuator by providing one or more information sources as the present disclosure is not so limited.
In some embodiments, a control method similar to that of
In some embodiments, a controller of the haptic actuator may control both of a heating membrane and vibrational actuator such that thermal and vibrations profiles may be applied to an adjacent surface in a cooperative manner. Without wishing to be bound by theory, certain combinations of vibration and heat may be associated with beneficial sensations to a wearer. For example, social touch which may be physiologically and/or psychologically beneficial may be associated with both vibration and heat. Accordingly, the controller may provide a desirable combination of vibrational and temperature profiles to the adjacent surface. In some embodiments, a vibrational period and a warmth period may at least partially overlap and/or may be applied separately. Of course, the vibrational and temperature profiles may be applied to an adjacent surface by the controller at any suitable time either simultaneously or separately.
As noted above, the currently disclosed systems may include a heating membrane architecture with a low effective heat capacity. In some embodiments, the conducting material used to provide the desired heating may be non-directional in its heating. Accordingly, to reach a desired temperature profile, the entirety of the membrane, including any associated insulation, interfacial materials, and supports associated with the membrane may be warmed. Without wishing to be bound by theory, the heat capacity of an object describes the amount of energy used to increase the temperature of an object by a given temperature increase, typically provided in Joules/Kelvin (J/K). In some embodiments, during the warmth period, a haptic actuator may generate dynamic temperature profiles with high rates of temperature change, between 0.05° C./s and 2° C./s, 0.1° C./s and 2° C./s, 0.5° C./s and 2° C./s, and/or any other appropriate rate of temperature change in order to generate strong sensations of warmth. Under conditions where dynamic temperature profiles are generated, the heat capacity of the membrane may be equivalent to the power used to generate a given rate of temperature change according to the following ratio:
where J is joules, s is second, K is degrees Kelvin, and W is Watts.
As one example of the significance of the relationship between heat capacity, power, and temperature change, two insulating layers with differing heat capacities for heating membranes are shown in Table 2 for a silicone layer and a polyimide film used to form heating membranes with a 5 cm2 surface area. Despite having a similar specific heat and density, a roughly ten times increase in thickness in the silicone layer relative to the polyimide film translates to a similar increase in added heat capacity of the heating membrane. Due to the relationship between heat capacity, power, and temperature changes, the silicone membrane used ten times more energy to reach a desired temperature and ten times more power was used to heat the membrane at a desired rate of temperature change. Accordingly, this comparison confirms that providing lower heat capacities and thermally isolating a heating membrane directly relates to a haptic actuator including improved high rate capabilities while providing lower power consumption.
While the present teachings have been described in conjunction with various embodiments and examples, it is not intended that the present teachings be limited to such embodiments or examples. On the contrary, the present teachings encompass various alternatives, modifications, and equivalents, as will be appreciated by those of skill in the art. Accordingly, the foregoing description and drawings are by way of example only.
This application claims the benefit under 35 U.S.C. § 119(e) of U.S. provisional application Ser. No. 62/791,134 filed Jan. 11, 2019, the disclosure of which is incorporated by reference in its entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2020/012311 | 1/6/2020 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62791134 | Jan 2019 | US |
