The present disclosure relates to systems, devices, and methods for printing in three dimensions, and more particularly relies on harnessing deformation, instability, and fracture of viscoelastic inks to improve the capabilities and versatility of direct ink writing, allowing for higher resolution, more diverse printing by a three dimensional printer without having to change the hardware of the printer to achieve the versatility.
There are a variety of techniques utilized to print three-dimensionally. One such technique is direct ink writing (DIW), which can allow for three-dimensional (3D) printing of multi-material and multi-functional structures capable of being used in diverse fields including stretchable electronics, organ on a chip, soft robotics, biomedical implants, and smart composites, among others. The materials that can be used in such multi-material printing include conductive pasts, elastomers, and hydrogels. During DIW printing, pressurized viscoelastic inks are extruded out of one or more nozzles, such as nozzles associated with a printhead, in the form of printed fibers. The fibers can be deposited into patterns based on a prescribed motion of the nozzles. In most DIW printing processes, a single set of printing conditions is adopted through trials and errors, and such conditions are rarely changed during the printing process. As a result, the resolution of printed fibers is usually limited by the nozzle's diameter, and the printer pattern is limited by the nozzle's motion paths. Such limitations have greatly restricted the versatility and applications of DIW three-dimensional printing approaches.
Accordingly, there is a need to improve DIW three-dimensional printing systems and methods to allow for more versatility in the types of objects that can be printed without sacrificing efficiency (i.e., without having to change hardware during the printing process) so the resulting printed objects can be of a better quality and be more dynamic.
DIW three-dimensional printing systems and methods are provided in the present disclosure that are clear improvements over existing DIW systems and methods at least because they are more versatile, thus allowing for quicker and higher quality production of three-dimensional objects. These improvements result from harnessing characteristics and properties of viscoelastic materials (e.g., viscoelastic inks) such as deformation, instability, and fracture to provide parameters under which various configurations of printed fibers can be produced. The dimensionless parameters relate to a speed of extrusion (e.g., the speed of the nozzle and the speed at which the material is deposited out of the nozzle), referred to herein as the dimensionless parameter V*, and a height of a nozzle with respect to a surface or material onto which the material is being deposited, referred to herein as the dimensionless parameters H*. The printed fiber configurations provided include, but are not limited to: accumulation, translating coiling, alternating coiling, stretching coiling, meandering, die-swelling, equi-dimensional, thinning, and discontinuous, among other possible printing modes. Although the present disclosure primarily describes the properties of deformation, instability, and fracture being associated with viscoelastic materials, a person skilled in the art will recognize other materials may also have such properties that can be harnessed in a manner similar to as provided for herein without departing from the spirit of the present disclosure.
The provided systems and methods allow for highly tunable and repeatable printing, and permit the ability to print stretchable structures with tunable stiffening, as well as 3D structures with gradient properties and programmable swelling properties. To the extent such structures can printed three-dimensionally using known systems and methods, such systems and methods are generally not capable of such versatility, tenability, and repeatability using a single nozzle, or a combination of single nozzles that each have this capability. Rather, previously existing systems and methods typically rely on changes to hardware (e.g., different nozzles) to achieve the printed fibers that are produced in accordance with the present disclosures.
In one exemplary embodiment of a method for printing in three dimensions, the method includes selecting a printing mode based on at least one of a non-dimensional nozzle speed and a non-dimensional nozzle tip height. The non-dimensional nozzle speed is based on both a nozzle speed and an extrusion speed, while the non-dimensional nozzle tip height is based on both a die-swollen diameter of material to be extruded from a nozzle and a combination of a height of a substrate configured to receive extruded material from the nozzle and a height of material disposed on the substrate. The method also includes depositing material from the nozzle based on the selected printing mode.
Depositing material from the nozzle based on the selected printing mode can include depositing the material in one or more of the following manners: accumulation, translating coiling, alternating coiling, stretching coiling, meandering, die-swelling, equi-dimensional, thinning, and discontinuous, among others. Selecting a printing mode based on at least one of a non-dimensional nozzle speed and a non-dimensional nozzle tip height can include selecting values of at least one of the non-dimensional nozzle speed and the non-dimensional nozzle tip height based on at least one of the following properties of the material to be deposited from the nozzle: a deformation of the material, an instability of the material, and/or a fracture of the material. The material that is deposited can include a viscoelastic ink.
The method can include generating a phase diagram for material to be printed from the nozzle. The phase diagram can include a plurality of printing modes from which the printing mode can be selected based on the non-dimensional nozzle speed and the non-dimensional nozzle tip height. At least one printing mode can be based on a ratio that includes the non-dimensional nozzle speed and the non-dimensional nozzle tip. Additionally, or alternatively, at least one printing mode can be based on a comparison between the non-dimensional nozzle speed and a die-swelling ratio. Still further additionally, or alternatively, at least one printing mode can be based on a comparison between the non-dimensional nozzle speed and the actual nozzle speed.
One exemplary embodiment of a three-dimensional printing system includes a printhead and a controller. The printhead includes one or more nozzles. The controller is configured to operate the printhead to eject ink from the one or more nozzles towards a surface. The controller is further configured to print in a variety of different printing modes without changing hardware of the system, including hardware of the printhead and the one or more nozzles. While many different printing modes are achievable, they include accumulation, translating coiling, alternating coiling, stretching coiling, meandering, die-swelling, equi-dimensional, thinning, and discontinuous.
In some embodiments, the controller can be configured to print at least each of the variety of different printing modes. Those modes can include accumulation, translating coiling, alternating coiling, stretching coiling, meandering, die-swelling, equi-dimensional, thinning, and discontinuous, among others. Ink ejected by the one or more nozzles can include a viscoelastic ink. In some embodiments, the system can include a viscoelastic ink, with the viscoelastic ink being configured to be the ink ejected by the one or more nozzles.
The controller can be further configured to select a printing mode from the variety of different printing modes. The selection can be based on at least one of a non-dimensional nozzle speed and a non-dimensional nozzle tip height of at least one nozzle of the one or more nozzles. The non-dimensional nozzle speed can be based on both a nozzle speed and an extrusion speed, and the non-dimensional nozzle tip height can be based on both a die-swollen diameter of material to be extruded from the at least one nozzle and a combination of a height of a substrate configured to receive extruded material from the at least one nozzle and a height of material disposed on the substrate. In some such embodiments, the controller can be configured such that it selects values of at least one of the non-dimensional nozzle speed and the non-dimensional nozzle tip height based on at least one of the following properties of the material to be deposited from the nozzle: a deformation of the material, an instability of the material, and/or a fracture of the material.
In some embodiments, the controller can be configured to generate a phase diagram for material to be printed from the one or more nozzles. The phase diagram can include at least one printing mode from the variety of different printing modes. The phase diagram can be based on at least one of a non-dimensional nozzle speed and a non-dimensional nozzle tip height of at least one nozzle of the one or more nozzles. The non-dimensional nozzle speed can be based on both a nozzle speed and an extrusion speed, and the non-dimensional nozzle tip height can be based on both a die-swollen diameter of material to be extruded from the at least one nozzle and a combination of a height of a substrate configured to receive extruded material from the at least one nozzle and a height of material disposed on the substrate. At least one printing mode can be based on a ratio that includes the non-dimensional nozzle speed and the non-dimensional nozzle tip. Additionally, or alternatively, at least one printing mode can be based on a comparison between the non-dimensional nozzle speed and a die-swelling ratio. Still further additionally, or alternatively, at least one printing mode can be based on a comparison between the non-dimensional nozzle speed and the actual nozzle speed.
Another exemplary embodiment of a three-dimensional printing system includes both a controller and one or more nozzles. The controller is configured to select a printing mode based on at least one of a non-dimensional nozzle speed and a non-dimensional nozzle tip height. The non-dimensional nozzle speed is based on both a nozzle speed and an extrusion speed, and the non-dimensional nozzle tip height is based on both a die-swollen diameter of material to be extruded from a nozzle and a combination of a height of a substrate configured to receive extruded material from the nozzle and a height of material disposed on the substrate. The one or more nozzles are for depositing material based on a print mode selected by the controller.
The controller can be configured to select a print mode from a plurality of print modes, the plurality of print modes including: accumulation, translating coiling, alternating coiling, stretching coiling, meandering, die-swelling, equi-dimensional, thinning, and discontinuous, among others. Alternatively, or additionally, the controller can be configured such that it selects values of at least one of the non-dimensional nozzle speed and the non-dimensional nozzle tip height based on at least one of the following properties of the material to be deposited from the nozzle: a deformation of the material, an instability of the material, and/or a fracture of the material. The one or more nozzles can be configured to deposit a viscoelastic ink based on a print mode selected by the controller. In some embodiments, the system includes a viscoelastic ink, with the viscoelastic ink being configured to be deposited by the one or more nozzles.
In some embodiments, the controller can be configured to generate a phase diagram for material to be printed from the one or more nozzles. The phase diagram can include a plurality of printing modes from which the printing mode is selected. The phase diagram can be based on the non-dimensional nozzle speed and the non-dimensional nozzle tip height of at least one nozzle of the one or more nozzles. The non-dimensional nozzle speed can be based on both a nozzle speed and an extrusion speed, and the non-dimensional nozzle tip height can be based on both a die-swollen diameter of material to be extruded from the at least one nozzle and a combination of a height of a substrate configured to receive extruded material from the at least one nozzle and a height of material disposed on the substrate. At least one printing mode can be based on a ratio that includes the non-dimensional nozzle speed and the non-dimensional nozzle tip. Additionally, or alternatively, at least one printing mode can be based on a comparison between the non-dimensional nozzle speed and a die-swelling ratio. Still further additionally, or alternatively, at least one printing mode can be based on a comparison between the non-dimensional nozzle speed and the actual nozzle speed.
This disclosure will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings, in which:
Certain exemplary embodiments will now be described to provide an overall understanding of the principles of the structure, function, manufacture, and use of the devices and methods disclosed herein. One or more examples of these embodiments are illustrated in the accompanying drawings. Those skilled in the art will understand that the devices and methods specifically described herein and illustrated in the accompanying drawings are non-limiting exemplary embodiments and that the scope of the present disclosure is defined solely by the claims. The features illustrated or described in connection with one exemplary embodiment may be combined with the features of other embodiments. Such modifications and variations are intended to be included within the scope of the present disclosure. Further, in the present disclosure, like-numbered components of various embodiments generally have similar features when those components are of a similar nature and/or serve a similar purpose.
The present disclosure provides systems and methods for using producing a three-dimensional structure having varied printed fiber configurations generated by a single nozzle in a continuous manner, without having to adjust the hardware of the system during the printing process. The systems and methods harness deformation, instability, and fracture of viscoelastic materials to adjust dimensionless parameters related to a speed of extrusion (e.g., the speed of the nozzle and the speed at which the material is deposited out of the nozzle), referred to herein as the dimensionless parameter V*, and a height of a nozzle with respect to a surface or material onto which the material is being deposited, referred to herein as the dimensionless parameters H*, to alter the printed fiber configurations. A phase diagram can be used to help outline the impact the dimensionless parameters on the resulting printed fiber configurations. The printed fiber configurations described herein include, but are not limited to: accumulation, translating coiling, alternating coiling, stretching coiling, meandering, die-swelling, equi-dimensional, thinning, and discontinuous, among other possible printing modes.
The present disclosure allows for highly tunable and repeatable printing, and also permits the ability to print stretchable structures with tunable stiffening and 3D structures with gradient properties and programmable swelling properties. All of these results can be achieved using a single nozzle, although multiple nozzles can be used to increase throughput. As a result, new printing strategies and formations can be achieved in direct image writing 3D printing, which can be applied across many different industries.
Direct Ink Writing Printing Devices and Systems
Direct ink writing (DIW) three-dimensional (3D) printing devices and systems come in a variety of configurations. The present disclosures allow for existing DIW printing devices and systems to be modified to operate in an improved manner, and the present disclosures also allow for newly configured DIW printing devices and systems.
As shown, the DIW 3D printing system 100, also referred to as a printer, printing device, or device, includes a base 110, a receiving plate 120, a printhead support 130, a printhead 140, and a controller 160. The base 110 provides support for the receiving plate 120, and includes one or more tracks 112 along which the receiving plate 120 can be moved. In the illustrated embodiment, the track 112 allows for movement of the plate 120 along an illustrated Y-axis. Other tracks can be provided to allow movement of the plate 120 along an illustrated X-axis and/or an illustrate Z-axis. Further, movement of the plate 120 is not limited to along straight axes, as in other embodiments the system 100 can be configured to allow for 360° movement of the plate 120 with respect to the base 110 along and between any of the X, Y, and Z axes. A person skilled in the art will recognize many ways by which the plate 120 can be actuated to move along the track 112 (e.g., use of one or more motors, and/or other mechanical, electro-mechanical, or electrical systems), and thus a further description of how movement of the plate 120 with respect to the base 110 is implemented is unnecessary.
In addition to being configured to be moved with respect to the base 110, the receiving plate 120 can be configured to receive one or more printed fibers from the printhead 140. In some embodiments the plate 120 may include a designated print area. That print area can be the entirety of the plate 120, or some subpart thereof. The designated print area can be demarcated in some fashion, such as with a different color or by forming a raised or lowered surface around a perimeter of the print area, and can include other features that help define a print area. In some embodiments, a surface of the receiving plate 120 can be treated to allow it to be conducive to maintaining a location of a printed fiber, while also allowing the printed fiber to be separated from the receiving plate 120 in an easy manner so as not to harm the printer object when it is completed and ready to be removed from the receiving plate 120. In some embodiments, the plate 120 comprises a substrate, and it can wholly be a substrate.
The printhead support 130 is a structure that is disposed in a manner that is substantially perpendicular to the base 110 (and thus the receiving plate 120 in the illustrated embodiment). Other configurations between the support 130 and the base 110 are certainly possible without departing from the spirit of the present disclosure. As shown, the support 130 includes a track 132 that allows for movement of the printhead 140 along the illustrated X-axis. Further, because the printhead support 130 extends vertically above the base 110, the printhead 140 is also located a distance above the base 110, i.e., along the illustrated Z-axis. Still further, the illustrated embodiment provides for a second track 134 that allows for movement of the printhead 140 along the illustrated Z-axis. Like with the illustrated movement of the plate 120 along the X-axis, movement of the printhead 140 is not limited to movement along one or more of the axes, as in alternative configurations movement can be in more of a freeform manner (i.e., not restricted to a track) such that it can have 360° of movement with respect to any of the base 110, the plate 120, and/or the support 130. Further, a person skilled in the art will recognize many ways by which the printhead 140 can be actuated to move along the tracks 132, 134 (e.g., use of one or more motors, and/or other mechanical, electro-mechanical, or electrical systems), and thus a further description of how movement of the printhead 140 with respect to any of the base 110, the plate 120, and/or the support 130 is implemented is unnecessary.
The printhead 140 can include one or more nozzles 150 for ejecting material towards the receiving plate 120 to produce one or more fibers for use in constructing, i.e., printing, a three-dimensional object. In the illustrated embodiment, there are four nozzles 150, each extending in a row along the illustrated X-axis. In other embodiments, one or more nozzles can extend along other axes, or anywhere on the printhead 140, even if not along one of the illustrated axes. For example, a second row of nozzles can be provided along the X-axis, but a distance further along the Y-axis from the support 130. The nozzles 150 can be integrally formed with respect to the printhead 140, or they can be removable and replaceable, thereby allowing different nozzle configurations to be used. In some embodiments, the nozzles 150 can be configured to move along the illustrated Z-axis, in addition to or in lieu of the printhead 140 moving along the Z-axis in view of the track 134. A person skilled in the art will recognize how printheads and nozzles are generally constructed and operated, and thus additional details about their structure and function, apart from the highlighted features described below, are unnecessary.
Notably, although the illustrated embodiment provides for a plurality of nozzles 150, one feature of the present disclosure is the fact that a single nozzle can be operated to achieve different configurations of printed fibers in a continuous manner, without modifying the nozzle itself or using other nozzles. Accordingly, a system 100 that utilizes a single nozzle can perform the functions provided for herein. When a printing system in accordance with the present disclosure includes multiple nozzles, it can allow for quicker, more diverse printing because one or more of those nozzles, including all of those nozzles, can be operable in accordance with the present disclosures to allow for different configurations of printed fibers to be printed in a continuous manner, without modifying the nozzles or using the surrounding nozzles to create the different configurations. The illustration of a system having multiple nozzles is in no way limiting, and thus a system including a single nozzle is likewise a preferred embodiment, as is a system having multiple nozzles. There is no real upper limit to the number of nozzles that can be part of a printing system where the nozzles incorporate the printing techniques disclosed herein. Further, to the extent the descriptions below are described as being applied to a single nozzle, a person skilled in the art will recognize the descriptions can be applied to a plurality of nozzles. For example, more than one nozzle can be moved at particular speeds (e.g., the speed V), can extrude material at a particular speed (e.g., the speed C), and/or can be raised or lowered to particular heights (e.g., the height H) simultaneously, allowing for quicker manufacture of a part having identical printed fiber locations in at least some portions of the object being printed.
The nozzle(s) 150 can be used to extrude, or otherwise deposit, a material onto the receiving plate 120. This material can be a viscoelastic ink, which is a material having both viscous and elastic properties. Viscoelastic inks can have a variety of make-ups or configurations, and in some embodiments the inks can have at least one of a polymer base, a nano-particle filler, or a micro-particle filler. Viscoelastic inks can exhibit characteristic responses during flow or injection for printing such as shear yield-stress and/or shear thinning.
The controller 160 helps to operate components of the system 100, such as the printhead 140 and/or plate 120, by providing printing commands to one or more components of the system 100. The printing commands can include any command related to the operation of system 100, including but not limited to: commands that cause the printhead 140 to move with respect to the base 110, the plate 120, and the support 130; commands related to extrusion of material from the nozzle(s) 150, such as controlling parameters like the speed C at which the extrusion occurs, a speed V at which the nozzle(s) 150 moves (and thus the dimensionless parameter V*, which is a function of the speed V and the speed C, as described below), and a height H of the nozzle(s) 150 with respect to the surface onto which the extruded material is being printed (e.g., the receiving plate 120 and/or one or more previously printed layers of printed fibers) (and thus the dimensionless parameter H*, which is a function of the height H, among other parameters, as described below); and/or commands related to other components of the system to allow movement with respect to the printhead 140, such as commands to move the plate 120 along the track 112). Thus, it is the controller 160, or a person or machine operating the controller 160, that can change the parameters to provide various printing modes, such parameters and printing modes being described in greater detail below. The controller 160, or person or machine operating the controller 160, can more generally select a desired printing mode(s), and the controller 160 can then implement changes to one or more parameters to achieve the desired printing mode(s). A person skilled in the art will understand many different commands that can be controlled or otherwise implemented by the controller 160 in view of the present disclosures.
In the embodiment provided for in
A person skilled in the art will appreciate may different sizes, shapes, and materials can be used to make the various components of the DIW 3D printing system 100. For example, although in the illustrated embodiment the base 110 and the plate 120 are substantially rectangular in shape, a variety of shapes (e.g., circular, triangular, trapezoidal, other polygons) can be used in conjunction with the base 110 and the plate 120. The shapes of the various components do not have to be the same either, so the base 110 can be rectangular while the receiving plate 120 can be hexagonal. Standard materials can be used to make any of the various components of the DIW 3D printing system 100. For example, a stainless steel or titanium alloy, among other materials, can be used to form components like the base 110, plate 120, and printhead support 130. A person skilled in the art will recognize such suitable materials for the various components, and thus additional descriptions of the same is unnecessary.
Although
Nozzle(s)
Q=πC(αD)2/4. (1)
The nozzle tip can move at a speed of V and a height of H (from the surface of the plate 120 or printed layers disposed on the plate 120) while depositing fibers of the viscoelastic ink. In conventional DIW 3D printing, the moving speed of the printer nozzle V is set to be equal to C. As a result, the resolution of printed fibers is limited to αD, and the printed pattern is controlled by the continuous motion path of the nozzle 250. A person skilled in the art will recognize that a value of C is typically determined by material properties of the ink and applied pressure P during DIW 3D printing.
Distinct from conventional DIW 3D printing, the systems and methods provided for herein allow a single nozzle to print fibers with various diameters much smaller than αD, significantly enhancing the resolution of DIW printing. Further, the systems and methods provided for herein allow for a printed fiber that can be discontinuous despite providing for continuous motion of the nozzle. Still further, the systems and methods provided for herein allow for the creation of complex patterns of printed fibers that can be achieved with simple straight nozzle motions.
Non-Dimensionalized Printing Parameters
As provided for herein, it is possible to control two non-dimensionalized printing parameters to achieve the desired results of improved DIW 3D printing systems and methods. The two non-dimensionalized printing parameters are:
with V* representing the non-dimensional nozzle speed and H* representing the non-dimensionalized nozzle tip height. In conventional DIW 3D printing, the printing parameters V* and H* are commonly set to be unity so that the extruded viscoelastic ink is deposited without significant deformation. The present disclosure, on the other hand, tunes at least one of V* and H* to exploit deformation, instability, and fracture of viscoelastic inks. Such tuning can occur across wide value ranges, and the tuning can enable new modes of DIW 3D printing, which include accumulation, coiling, die-swelling, equi-dimensional, thinning, and discontinuous modes (see
More particularly,
Exturded Material, Including Viscoelastic Inks, and the Formation of Printed Fibers
As discussed above, a variety of viscoelastic inks can be employed in conjunction with the present disclosures. The mechanics of viscoelastic inks help to achieve the very benefits described herein. This is due, at least in part, to their properties, including their viscoelasticity, shear thinning, and yield stress flow. Properties of the material more generally, including a deformation of the material, an instability of the material, and a fracture of the material, can impact the resulting printed fiber. Accordingly, the system (e.g., the system 100), via components such as a controller (e.g., the controller 160) and/or an operator of the system, can be configured to select values of various parameters based on the properties of the material being extruded. A person skilled in the art, in view of the present disclosures, will recognize that the values of the dimensionless parameters H*, V* can vary depending on the material used, among other factors that may impact the parameter values. The boundaries for the various modes depend, at least in part, on the material of the property, among other factors discussed herein or otherwise understood by a person skilled in the art in view of the present disclosures. For example, as illustrated in
As illustrated in
As provided for herein, a controller (e.g., the controller 160) can alter the various parameters of the dimensionless parameters V* and H* to achieve various printing modes. Any of the variables that correlate to such parameters can be altered by the controller. Accordingly, while it may be more conventional and/or easy to alter the height H of the dimensionless parameter H*, in some embodiments a system can be configured such that the controller, or another component associated with the controller, can alter either or both of the die-swelling ratio α of the material and the inner diameter D of the nozzle to provide for a different value of the dimensionless parameter H*. For example, in some instances a nozzle may be configured such that its inner diameter D can be altered while in operation.
When the gravitation stretching is negligible, the radius of steady coiling can scale with the nozzle tip height, Rc˜H, and therefore, Ωc˜C/H. With this relation, the translational movement of the nozzle during each cycle of coiling can be expressed as VΔt, where Δt˜1/Ωc. As shown in
where the diameter of printed fiber d=αD/√{square root over (V*)} calculated from the volume conservation of the extruded ink) can be much greater than nozzle inner diameter D due to the accumulation of ink.
Because the boundary between accumulation and coiling mode is given as V*=1/H*, the complete condition for the coiling mode of printing becomes:
where the diameter of printed fiber d is equal to the die-swollen diameter αD. The coiling mode generally requires H*>1 because the deposited ink is typically squeezed between the nozzle tip and the substrate or printed layers when H*≤1.
When V*>1, the extruded viscoelastic ink can start to get stretched due to the motion of the nozzle, as illustrated in
which agrees reasonably well with experimental data for H*=2, 4 and 6, which is illustrated in
respectively. Assuming incompressibility and volume conservation of the extruded ink, the diameter of the printed fiber 472 can be calculated as d=αD/√{square root over (V*)}. According to the normalized nozzle speed, the die-swelling mode can be classified as:
1<V*<α2 (5)
where the die-swelling effect is dominant and the diameter of printed fiber d is greater than nozzle inner diameter D.
Further, according to the normalized nozzle speed, the equi-dimensional mode can be classified as:
V*=α2 (6)
where the diameter of printed fiber d is equal to nozzle inner diameter D.
Still further, according to the normalized nozzle speed, the thinning mode can be classified as:
α2<V*<V*f (7)
where the diameter of printed fiber d can be much smaller than nozzle inner diameter D, enhancing the resolution of the printing. In Equation (7), V*f is the non-dimensional nozzle speed at which the extruded ink starts to undergo fracture. Hence, the upper limit of the thinning mode is given as V*=V*f. It should be noted that V*f is a material property, given that the Weissenberg number is greater than one. For example, the experimental measurements give V*f≈3.5 for a silicone elastomer ink (e.g., SE 1700; Dow Corning and Dragon Skin; Smooth-On), and V*f≈30 for a hydrogel ink (PEO solution). Accordingly, by adopting a thinning mode of printing, the resolution of the printed fibers can be enhanced up to about 1.9 times and about 5.4 times for the silicone elastomer and the hydrogel inks, respectively.
When the nozzle speed exceeds V*f, the thinning of extruded ink by stretching transits to the fracture of stretched ink, resulting in discontinuous patterns of printed fiber segments, as illustrated in
V*f≤V* (8)
where the diameter of printed fiber d reaches its minimum value αD/√{square root over (V*f)} as the fiber cannot be further stretched.
Phase Diagram
As shown, the dimensionless parameter V* is plotted on the Y-axis and the dimensionless parameter H* is plotted on the X-axis. Schematic illustrations of the various printing modes to clearly illustrate the configuration of the resulting printed fiber are provided at the right.
As shown, a discontinuous printing mode or configuration is achieved when V* is greater than or equal to approximately Vf*, where Vf* is the non-dimensional nozzle speed at which the extruded viscoelastic ink starts to undergo fracture, which is a material property of a specific viscoelastic ink. As V* becomes approximately less than Vf*, the printing mode can shift to a thinning printing mode or configuration. As shown, thinning occurs when V* is greater than or equal to approximately the square of the die-swelling ratio (α2), with V* being approximately less than Vf*. The printing mode or configuration becomes equi-dimensional when V* approximately equals α2, and a die-swelling printing mode or configuration results when V* is approximately greater than or equal to 1 and less than approximately α2.
In the illustrated phase diagram, various coiling configurations begin when V* is less than approximately 1. As shown, a meandering printing mode or configuration can occur when V* is greater than approximately 0.53 and less than approximately 1, a stretching coiling printing mode or configuration can occur when V* is greater than approximately 0.55 and less than approximately 0.68, an alternating coiling printing mode or configuration can occur when V* is greater than approximately 0.28 and less than approximately 0.6, and a translating coiling printing mode or configuration can occur when V* is greater than approximately 0 and less than approximately 0.33. Notably, there is overlap in these numbers for each mode, but each mode can also be assigned to unique narrower ranges without overlap. A person skilled in the art will recognize how various modes can be inter-mixed when transitioning from one more to the next by choosing appropriate combinations of V* and H* for each mode in view of the present disclosures. Finally, as shown, accumulation can result when the dimensionless parameter V* is less than or equal to the inverse of the dimensionless parameter H* (i.e., 1/H*). Further, as illustrated, coiling instability develops as the value for H* gets greater.
A person skilled in the art will recognize that the phase diagram of
Experimental Validation of Printing Methods
The use of the non-dimensional printing parameters (H*, V*) to achieve particular fiber configurations, and in particular the values of those parameters that can be used to achieve those parameters, were further validated by experimental testing. These experiments were performed using a systematic set of experiments for various combinations of H* and V* with a silicone elastomer ink (in the experiments, SE 1700; Dow Corning and Dragon Skin; Smooth-On).
Printing Methods with a Variety of Diameters
The systems and methods provided for herein can be used in conjunction with printing fibers of various diameters. This is because the present disclosures are not limited by nozzle diameter. Complex patterns with straight nozzle motions can be achieved with diameters of various thickness when the present teachings are utilized. Furthermore, the transition between different modes or configurations (e.g., translating coiling, stretching coiling, meandering, die-swelling, equi-dimensional, thinning, etc.) can be continuous, enabling the continuous printing of various non-linear patterns and fiber diameters by one nozzle in undisrupted manner.
For example, as illustrated in
Printing 3D Structures
The capability of tuning fiber diameters in a highly reproducible and predictable manner allows for improved printing of three-dimensional objects or structures, including solid structures. The resulting structures can have varying resolutions and layer thickness using a single nozzle.
As shown in
In addition to the varied structures now possible in view of the present disclosures, methods for printing in three dimensions can likewise be improved. Such methods can include selecting printing modes based on the non-dimensional parameters V* and H*, and the parameters that impact these non-dimensional parameters. The selection can be done manually, by an operator, or can be automated, such as by a controller. The controller may receive desired parameters (e.g., V*, H*, and parameters that impact V* and H*) and print based on those parameters, or in the alternative, the controller can receive a desired result, such as desired printing mode to be achieved or a desired property for the resulting printed material to have (e.g., a certain level of stiffness, a particular formation or shape, etc.), and adjust the parameters (e.g., V*, H*, and parameters that impact V* and H*) to achieve the desired result. After the printing mode is selected, the material can be deposited from one or more nozzles based on the selected printing mode. The depositing can thus be done using any of the printing modes provided for herein, or otherwise derivable from the present disclosures, including: accumulation, translating coiling, alternating coiling, stretching coiling, meandering, die-swelling, equi-dimensional, thinning, and discontinuous. As discussed elsewhere, the controller can be capable of generating a phase diagram, like those provided for in
Applications and Functionalities
The present disclosures allow for various applications and functionalities that were not achievable using conventional DIW printing. The ability to print diverse complex patterns with linear nozzle paths by coiling instability allows for new avenues to fabricate stretchable structures with tunable stiffening properties. For example, biological tissues can be fabricated that allow for the tissues to achieve delayed stiffening under deformation, similar to how natural biological tissue acts. This ability plays a critical role in the functionalities and structural robustness of the tissue.
The present disclosures can be useful in various engineering applications, such as creating stretchable electronics. The fabrication of stretchable electronics prior to the present disclosure typically requires complicated, multi-step processes in small scales. However, in view of the present disclosures, stretchable structures with tunable stiffening property can readily be printed by harnessing instability of the viscoelastic ink. This is illustrated in
As shown in
Additionally, the same approach can realize structures with anisotropic stiffening property in different directions, all printed with a single nozzle. In one example, V* is selected to be 0.8 for both X and Y directions to create a meandering pattern or mode in both directions, resulting in the delayed stiffening responses in both directions, as shown in
The present disclosures also allow 3D structures with gradient properties to be produced. In conventional DIW printing, the printing of fibers with large range of diameters typically requires individually accessible nozzles with different diameters. The predictable control of fiber diameter afforded by the present disclosures, however, allows for a wide range of fiber diameters to be achieved without changing the nozzle. Instead, the printing parameters can be adjusted to achieve different diameters across a single fiber. More specifically, such gradient structures can be printed within the same layer of fibers by varying H* and V* when printing different fibers. For example, in some embodiments, such as a gradient mesh 1000 illustrated in
The gradient can also be introduced over different layers in a 3D structure by using different H* and V* values in different layers. For example, to print a 3D structure with different patterns and fiber diameters for each layer as shown in
Further support for the delayed stiffening is provided for in
λL=λL0/V* (9)
where λL0 is the locking stretch of the fiber printed at V*=1. Delayed stiffening happens under tension due to initial stretching of the meandering patterns with low resistance. The delay stiffening is highly tunable in view of the present disclosures by selecting appropriate printing parameters based on a phase diagram.
The 3D structures that can be printed as a result of the provided systems and methods can also have gradient kinetic properties that enable functions not previously achievable for 3D structures generated by DIW printing. For example, structures can be produced using fibers with different diameters have different equilibrium swelling time t, following the quadratic diffusion relation t˜d2 shown in
As a result, as shown in
One skilled in the art will appreciate further features and advantages of the disclosure based on the above-described embodiments. Accordingly, the disclosure is not to be limited by what has been particularly shown and described, except as indicated by the appended claims. All publications and references cited herein are expressly incorporated herein by reference in their entirety.
The present application is a U.S. national stage of and claims priority to International Patent Application No. PCT/US18/63697, filed Dec. 3, 2018, and titled “Systems, Devices, and Methods for 3D Printing by Harnessing Deformation, Instability, and Fracture of Viscoelastic Inks,” which claims priority to and the benefit of U.S. Provisional Application No. 62/594,516, filed Dec. 4, 2017, and titled “Systems, Devices, and Methods for 3D Printing by Harnessing Deformation, Instability, and Fracture of Viscoelastic Inks,” the contents of each which is hereby incorporated by reference in their entireties.
This invention was made with Government support under Grant No. CMMI 1661627 awarded by the National Science Foundation, and under Grant No. N00014-17-1-2920 award by the Office of Naval Research. The Government has certain rights in the invention.
Filing Document | Filing Date | Country | Kind |
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PCT/US18/63697 | 12/3/2018 | WO | 00 |
Number | Date | Country | |
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62594516 | Dec 2017 | US |