Patent Application
20230341355
The present disclosure generally relates to sensor systems and methods of use thereof.
Hydrogels are crosslinked polymer networks that contain high water content. The past two decades have seen a sharp rise in fundamental research involving hydrogels and the development of hydrogels for various applications in energy storage and biotechnology (Madhumitha et al. 2018, Stephan 2006, Wu et al. 2013, Xu et al. 2013) The need for controlled drug release systems was among the earliest driving forces for hydrogel research in the pharmaceutical sciences (Gupta et al. 2002). In addition to the ability to incorporate drugs, the ability to incorporate animal cells has led to the widespread use of hydrogels in 3D cell culture and tissue engineering applications (Lee et al. 2008, Tibbitt et al. 2009). For example, a number of studies have shown that the gene expression profiles of cells differ in monolayer tissue culture environments (i.e., 2D substrates) vs. 3D matrices, which is often attributed to differences in cell-cell and cell-matrix interactions (Tibbitt et al. 2009). Hydrogels have emerged as attractive materials for regenerative medicine applications, including 3D-bioprinted tissues and injectable scaffolds for wound healing and tissue regeneration (Duan et al. 2013, Haring et al. 2017, Haring et al. 2019, Highley et al. 2015). In combination with their use as energy storage devices (e.g., gel electrolytes for lithium ion batteries), (Stephan 2006, Wu et al. 2013) passive drug release systems, (Gupta et al. 2002, Li et al. 2016) tissue scaffolds, (Drury et al. 2003, Lee et al. 2001), and sensors, (Gerlach et al. 2005, Richter et al. 2008) emerging applications to soft actuators, active drug release systems, and complex engineered tissues have driven research on stimuli-responsive hydrogels—for example, in soft robotics and 4D bioprinting fields (Bakarich et al. 2015, Gladman et al. 2016). In such applications, the characterization of hydrogel structure, physical properties, and rheological properties (e.g., crystal structure, dielectric properties, and viscoelastic properties) serve as important indicators of the material's processability, performance, quality, and response to stimuli. Therefore, identifying new paradigms for the characterization of hydrogels and other gel-based materials is central to accelerating the pace of gel-based materials research and improving the processability and quality of gel-based therapeutics, devices, and other products.
In one aspect of the disclosure, a system for measuring physical material properties of a plurality of samples includes a three-axis robotic structure for moving the target to a desired position in a three-dimensional space, a piezoelectric millimeter cantilever sensor mounted on the three-axis robotic structure, the piezoelectric millimeter cantilever sensor configured to have at least one electrical parameter as a function of its physical environment, and a controller coupled with the three-axis robotic structure. The controller is configured to instruct the three-axis robotic structure to position the millimeter cantilever sensor at a first position over a first well including a first fluid sample. The controller is further configured to instruct the three-axis robotic structure to lower the piezoelectric millimeter cantilever sensor into the first fluid sample, and instruct the three-axis robotic structure to retract the piezoelectric millimeter cantilever sensor from the first fluid sample and move the piezoelectric millimeter cantilever sensor over a second position over a second well including a second fluid sample. The controller is further configured to instruct the three-axis robotic structure to lower the piezoelectric millimeter cantilever sensor into the second fluid sample.
In some embodiments, the controller is further configured to measure at least one electrical parameter associated with the piezoelectric millimeter cantilever sensor when the piezoelectric millimeter cantilever sensor is lowered into each of the first fluid sample and the second fluid sample. In some embodiments, the controller is further configured to measure a first set of electrical parameters associated with the piezoelectric millimeter cantilever sensor after instructing the three-axis robotic structure to lower the piezoelectric millimeter cantilever sensor into the first fluid sample, determine that a value of at least one electrical parameter from the set of electrical parameters is in a steady state, and based on determining that the value is in a steady state, instruct the three-axis robotic structure to retract the piezoelectric millimeter cantilever sensor from the first fluid sample. In some embodiments, the controller is configured to determine that the value of the at least one electrical parameter from the set of electrical parameters is in the steady state based on determining that a rate of change of the value of the at least one electrical parameter from the set of electrical parameters is below a threshold value.
In some embodiments, the controller is further configured to prior to instructing the three-axis robotic structure to move the piezoelectric millimeter cantilever over the second position over the second well, instruct the three-axis robotic structure to lower and retract the piezoelectric millimeter cantilever sensor into a third well having a washing fluid. In some embodiments, the controller is further configured to determine that a value of at least one electrical parameter after instructing the three-axis robotic structure to retract the piezoelectric millimeter cantilever sensor from the first fluid sample, determine that the value of the at least one electrical parameter is below a threshold value, and based on determining that the value of the at least one electrical parameter is below the threshold value, instruct the three-axis robotic structure to lower the piezoelectric millimeter cantilever sensor into the third well having the washing fluid.
In some embodiments, the controller is further configured to repeatedly measure a value of at least one electrical parameter associated with the piezoelectric millimeter cantilever sensor after instructing the three-axis robotic structure to lower the piezoelectric millimeter cantilever sensor into the first fluid sample, and instruct the three-axis robotic structure to stop lowering the piezoelectric millimeter cantilever sensor into the first fluid sample upon determining that the value of the at least one electrical parameter is less than a submersion threshold value. In some embodiments, the system further includes a well plate including a plurality of wells, including the first well and the second well, each well of the plurality of well having an opening that can accommodate at least a portion of the piezoelectric millimeter cantilever sensor.
In another aspect of the disclosure a method for measuring material composition, structure, and properties of a plurality of samples uses a system including a three-axis robotic structure for moving the target to a desired position in a three-dimensional space, and a piezoelectric millimeter cantilever sensor mounted on the three-axis robotic structure, the piezoelectric millimeter cantilever sensor configured to have at least one electrical parameter as a function of its physical environment. The method includes positioning, by the three-axis robotic structure, the millimeter cantilever sensor at a first position over a first well including a first fluid sample. The method further includes lowering, by the three-axis robotic structure, the piezoelectric millimeter cantilever sensor into the first fluid sample. The method also includes retracting, by the three-axis robotic structure, the piezoelectric millimeter cantilever sensor from the first fluid sample and moving the piezoelectric millimeter cantilever sensor over a second position over a second well including a second fluid sample, and lowering, by the three-axis robotic structure, the piezoelectric millimeter cantilever sensor into the second fluid sample.
In some embodiments, the method further includes measuring at least one electrical parameter associated with the piezoelectric millimeter cantilever sensor when the piezoelectric millimeter cantilever sensor is lowered into each of the first fluid sample and the second fluid sample. In some embodiments, the method also includes measuring a first set of electrical parameters associated with the piezoelectric millimeter cantilever sensor after lowering the piezoelectric millimeter cantilever sensor into the first fluid sample, determining that a value of at least one electrical parameter from the set of electrical parameters is in a steady state, and retracting, based on determining that the value is in a steady state, the piezoelectric millimeter cantilever sensor from the first fluid sample.
In some embodiments, the method also includes determining that the value of the at least one electrical parameter from the set of electrical parameters is in the steady state based on determining that a rate of change of the value of the at least one electrical parameter from the set of electrical parameters is below a threshold value. In some embodiments, the method further includes prior to moving the piezoelectric millimeter cantilever over the second position over the second well, lowering, by the three-axis robotic structure, the piezoelectric millimeter cantilever sensor into a third well having a washing fluid. In some embodiments, the method also includes determining that a value of at least one electrical parameter retracting the piezoelectric millimeter cantilever sensor from the first fluid sample; determining that the value of the at least one electrical parameter is below a threshold value, and based on determining that the value of the at least one electrical parameter is below the threshold value, lowering, by the three-axis robotic structure, the piezoelectric millimeter cantilever sensor into the third well having the washing fluid. In some embodiments, the method further includes repeatedly measuring a value of at least one electrical parameter associated with the piezoelectric millimeter cantilever sensor after lowering the piezoelectric millimeter cantilever sensor into the first fluid sample, and stop lowering the piezoelectric millimeter cantilever sensor into the first fluid sample upon determining that the value of the at least one electrical parameter is less than a submersion threshold value.
In yet another aspect of the disclosure a non-volatile computer readable memory including instructions, which when executed by one or more processors, cause the one or more processors to execute a method. The method can include positioning, by a three-axis robotic structure, a millimeter cantilever sensor at a first position over a first well including a first fluid sample, wherein the three-axis robotic structure is configured to moving a target to a desired position in a three-dimensional space, and wherein the piezoelectric millimeter cantilever sensor is mounted on the three-axis robotic structure and is configured to have at least one electrical parameter as a function of its physical environment, lowering, by the three-axis robotic structure, the piezoelectric millimeter cantilever sensor into the first fluid sample, retracting, by the three-axis robotic structure, the piezoelectric millimeter cantilever sensor from the first fluid sample and moving the piezoelectric millimeter cantilever sensor over a second position over a second well including a second fluid sample, and lowering, by the three-axis robotic structure, the piezoelectric millimeter cantilever sensor into the second fluid sample.
In some embodiments, the method further includes measuring at least one electrical parameter associated with the piezoelectric millimeter cantilever sensor when the piezoelectric millimeter cantilever sensor is lowered into each of the first fluid sample and the second fluid sample. In some embodiments, the method also includes measuring a first set of electrical parameters associated with the piezoelectric millimeter cantilever sensor after lowering the piezoelectric millimeter cantilever sensor into the first fluid sample, determining that a value of at least one electrical parameter from the set of electrical parameters is in a steady state, and retracting, based on determining that the value is in a steady state, the piezoelectric millimeter cantilever sensor from the first fluid sample. In some embodiments, the method also includes determining that the value of the at least one electrical parameter from the set of electrical parameters is in the steady state based on determining that a rate of change of the value of the at least one electrical parameter from the set of electrical parameters is below a threshold value. In some embodiments, the method further includes prior to moving the piezoelectric millimeter cantilever over the second position over the second well, lowering, by the three-axis robotic structure, the piezoelectric millimeter cantilever sensor into a third well having a washing fluid.
Other systems, methods, features, and advantages will be or become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional systems, methods, features, and advantages be included within this description, be within the scope of the present disclosure, and be protected by the accompanying claims.
Further aspects of the present disclosure will be readily appreciated upon review of the detailed description of its various embodiments, described below, when taken in conjunction with the accompanying drawings.
Before the present disclosure is described in greater detail, it is to be understood that this disclosure is not limited to particular embodiments described, and as such may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting. The skilled artisan will recognize many variants and adaptations of the embodiments described herein. These variants and adaptations are intended to be included in the teachings of this disclosure.
All publications and patents cited in this specification are cited to disclose and describe the methods and/or materials in connection with which the publications are cited. All such publications and patents are herein incorporated by references as if each individual publication or patent were specifically and individually indicated to be incorporated by reference. Such incorporation by reference is expressly limited to the methods and/or materials described in the cited publications and patents and does not extend to any lexicographical definitions from the cited publications and patents. Any lexicographical definition in the publications and patents cited that is not also expressly repeated in the instant specification should not be treated as such and should not be read as defining any terms appearing in the accompanying claims. The citation of any publication is for its disclosure prior to the filing date and should not be construed as an admission that the present disclosure is not entitled to antedate such publication by virtue of prior disclosure. Further, the dates of publication provided could be different from the actual publication dates that may need to be independently confirmed.
Although any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present disclosure, the preferred methods and materials are now described. Functions or constructions well-known in the art may not be described in detail for brevity and/or clarity. Embodiments of the present disclosure will employ, unless otherwise indicated, techniques of nanotechnology, organic chemistry, material science and engineering and the like, which are within the skill of the art. Such techniques are explained fully in the literature.
It should be noted that ratios, concentrations, amounts, and other numerical data can be expressed herein in a range format. It is to be understood that such a range format is used for convenience and brevity, and thus, should be interpreted in a flexible manner to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. To illustrate, a numerical range of “about 0.1% to about 5%” should be interpreted to include not only the explicitly recited values of about 0.1% to about 5%, but also include individual values (e.g., 1%, 2%, 3%, and 4%) and the sub-ranges (e.g., 0.5%, 1.1%, 2.2%, 3.3%, and 4.4%) within the indicated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the disclosure, e.g. the phrase “x to y” includes the range from ‘x’ to ‘y’ as well as the range greater than ‘x’ and less than ‘y’. The range can also be expressed as an upper limit, e.g. ‘about x, y, z, or less’ and should be interpreted to include the specific ranges of ‘about x’, ‘about y’, and ‘about z’ as well as the ranges of ‘less than x’, less than y′, and ‘less than z’. Likewise, the phrase ‘about x, y, z, or greater’ should be interpreted to include the specific ranges of ‘about x’, ‘about y’, and ‘about z’ as well as the ranges of ‘greater than x’, greater than y′, and ‘greater than z’. In some embodiments, the term “about” can include traditional rounding according to significant figures of the numerical value. In addition, the phrase “about ‘x’ to ‘y’”, where ‘x’ and ‘y’ are numerical values, includes “about ‘x’ to about ‘y’”.
In some instances, units may be used herein that are non-metric or non-SI units. Such units may be, for instance, in U.S. Customary Measures, e.g., as set forth by the National Institute of Standards and Technology, Department of Commerce, United States of America in publications such as NIST HB 44, NIST HB 133, NIST SP 811, NIST SP 1038, NBS Miscellaneous Publication 214, and the like. The units in U.S. Customary Measures are understood to include equivalent dimensions in metric and other units (e.g., a dimension disclosed as “1 inch” is intended to mean an equivalent dimension of “2.5 cm”; a unit disclosed as “1 pcf” is intended to mean an equivalent dimension of 0.157 kN/m3; or a unit disclosed 100° F. is intended to mean an equivalent dimension of 37.8° C.; and the like) as understood by a person of ordinary skill in the art.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the specification and relevant art and should not be interpreted in an idealized or overly formal sense unless expressly defined herein.
The articles “a” and “an,” as used herein, mean one or more when applied to any feature in embodiments of the present invention described in the specification and claims. The use of “a” and “an” does not limit the meaning to a single feature unless such a limit is specifically stated. The article “the” preceding singular or plural nouns or noun phrases denotes a particular specified feature or particular specified features and may have a singular or plural connotation depending upon the context in which it is used.
While emerging synthetic techniques, such as automated synthesizers and synthetic biology, are now being developed to produce materials with unprecedented throughput, characterization loops represent major bottlenecks in accelerated molecular and material discovery workflows (de Pablo et al. 2019, Green et al. 2017, Zhang and Xiang 2017). For example, Green discusses the need to introduce new materials into the market faster and at lower costs based on the Materials Genome Initiative. This need is stymied by the lack of effective high throughput experimentation tools. In particular, there is lack of high throughput tools that can automatically and rapidly interrogate a library of samples for the properties of interest. Zhang and Xiang also discuss the long felt need for high throughput tools to measure mechanical properties. They present various microelectromechanical systems (MEMS) tools that can be utilized to measure the mechanical properties of several materials in parallel. However, there is still a dearth of tools that address measuring mechanical properties specifically, and material properties in general, in fluids with high throughput. The systems and method discussed herein fulfill the long-felt yet unmet need for high throughput tools for measuring material properties in fluids. The high throughput approach discussed herein is particularly beneficial in instances where the fluids, such as sol-gel fluids, are tested in microgravity environments, such as in space at e.g., the International Space Station. In such environments, it is important to have tools that provide the ability to measure material properties of a large number of fluids efficiently and reliably. The approach discussed herein can provide high throughput automated readings that require minimal assistance or control by a human.
The challenges associated with a lack of complementary, high-throughput characterization techniques are also compounded by the breadth of structure and property information that could be useful in assessing material performance and quality across different applications (Hoffman 2012, Li and Mooney 2016, Zhang and Khademhosseini 2017). In particular, the characterization of hydrogel viscoelastic properties, as well as of other soft materials, presents significant rate-limiting steps because of the requirement for manual sample preparation steps and the time-intensive nature of the tests. The gold-standard instruments for characterization of hydrogel viscoelastic properties are rheometers and dynamic mechanical analyzers (Brinson and Brinson 2015). While such instruments are robust and provide reliable information regarding the viscoelastic properties of a sample over a range of strain rates and temperatures, the samples must be manually prepared and measured to high tolerances, and experiments can take upwards of 0.5-1 day per sample, depending on the complexity and type of scan being performed. Additionally, such instruments are difficult to integrate with processes, which impedes applications that require viscoelastic property sensing or monitoring. As a result, it remains a pressing challenge to eliminate characterization bottlenecks from accelerated material discovery paradigms. In contrast to traditional characterization methods (e.g., dynamic mechanical analysis (DMA)), sensor-based characterization techniques offer measurement advantages associated with sensors, which include process integration through miniaturization and the ability for real-time process monitoring and control. Sensors can also offer improved sensitivity, limit of detection, throughput, and measurement repeatability relative to traditional methods through the use of sensitive miniaturized transducers and the elimination of manual sample preparation steps. Therefore, sensor-based techniques for characterization of hydrogel viscoelastic properties could provide useful tools for eliminating characterization bottlenecks that currently limit the pace of hydrogel materials research and development.
While various sensors have been created to measure the physical and rheological properties of liquids, (Abu-Zahra 2004, Jain et al. 2001, Jakoby and Vellekoop 2011, Kim 2002) milli- and micro-electromechanical systems have enabled the characterization of viscoelastic properties based on fluid-structure interaction effects (Mather et al. 2012). Thickness shear mode (TSM) resonators, such as quartz crystal microbalances (QCMs), were among the first sensors leveraged for viscoelastic property characterization. While TSM resonators enable the characterization of the viscoelastic properties of semi-infinite and thin layers of viscoelastic liquids, viscoelastic properties are obtained using equivalent circuit models, which imposes the requirement of sensor calibration. In addition to shear-mode resonators, dynamic-mode cantilevers have been extensively examined for sensor-based rheological and compositional analysis of liquids, such as viscosity monitoring, chemical sensing, and biosensing (Craighead 2007, Fritz 2008, Johnson and Mutharasan 2012, Lang et al. 2005, Raiteri et al. 2001, Singamaneni et al. 2008). Analysis of cantilever sensor response can be done using fluid-structure interaction models, which are the same physics that drive the sensor response, in contrast to equivalent circuit models, which are useful for modeling measurements based on impedance responses but are not directly representative of the physical phenomenon. The earliest applications of dynamic-mode cantilevers for characterizing the physical properties of liquids were focused on density monitoring using the well-known inviscid result (Chu 1963). In parallel with liquid density monitoring applications, rheological measurements (i.e., viscosity monitoring) were also performed using cantilever sensors by incorporating the frequency- and mode number-dependent hydrodynamic function. An explicit theoretical relationship between cantilever resonant frequency, quality factor, and the viscosity of the surrounding media has been previously reported (Sader 1998). For example, Chon et al. validated the theoretical results of the cantilever hydrodynamic function using an atomic force microscope (AFM) cantilever submerged in a range of viscous fluids (Chon et al. 2000). Boskovic et al. 2002 demonstrated that an AFM cantilever with a known undamped natural frequency (i.e., resonant frequency) and mass per unit length allowed for the simultaneous calculation of the density and viscosity of both gasses and liquids. Mather et al. extended the use of cantilever sensors for characterization and monitoring of the viscoelastic properties of liquids through the use of mesoscale piezoelectric cantilevers. (Mather, Rides, Allen and Tomlins 2012) In that study, the complex shear modulus was replaced with the viscosity in the previous models developed by Sader, (Sader 1998) Maali et al., (Maali et al. 2005) and Belmiloud et al., (Belmiloud et al. 2006) which yielded a system of equations for the determination of the shear storage and loss moduli of a material from the cantilever resonant frequency and quality factor responses (after accounting for the internal damping of the larger cantilever) (Mather et al. 2012). While Mather et al. were able to characterize the viscoelastic properties of a polyacrylamide solution, fluid damping effects impeded applications to characterization of more viscous or viscoelastic materials. Johnson and Mutharasan 2011 more recently showed that millimeter-scale cantilevers exhibited a sufficiently high cantilever Reynolds numbers to resonate in highly viscous liquids with dynamic viscosities as high as 103 cP. These studies suggest that millimeter-scale cantilevers could enable sensor-based characterization of solutions that undergo gelation, materials that exhibit sol-gel phase transitions, and the viscoelastic properties of gel-based materials.
As discussed herein, resonance in dynamic-mode cantilever sensors persists in hydrogels and enables the real-time characterization of hydrogel viscoelastic properties and the continuous monitoring of sol-gel phase transitions (i.e., gelation and dissolution processes). Real-time tracking of piezoelectric-excited millimeter cantilever (PEMC) sensor resonant frequency (e.g., fair=55.4±8.8 kHz; n=5 sensors) and quality factor (e.g., Q; Qair=23.8±1.5) can facilitate continuous monitoring of high-frequency hydrogel shear storage and loss moduli (G′f and G″f, respectively) calculated by sensor data and fluid-structure interaction models. Changes in the sensor phase angle, quality factor, and high-frequency shear moduli obtained at the resonant frequency (G′f and G″f) show strong correlation with low-frequency moduli obtained at 1 Hz using DMA.
Characterization studies were performed using physically and chemically crosslinked hydrogel systems, including gelatin hydrogels (e.g., 6-10 wt %) and alginate hydrogels (e.g., 0.25-0.75 wt %). The sensor exhibits a dynamic range from the rheological properties of inviscid solutions to hydrogels with high-frequency moduli of e.g., 70-90 kPa, or about 80 kPa and low-frequency moduli of e.g., 20-30 kPa or about 26 kPa. In some examples, the sensor can exhibit a limit of detection of 260 Pa and 1.9 kPa for changes in hydrogel storage modulus (E′) based on the sensor's phase angle and quality factor responses, respectively. The sensor data can facilitate quantitative characterization of gelation process dynamics using a modified Hill model. Thus, cantilever sensors provide a promising platform for sensor-based characterization of hydrogels, such as quantification of viscoelastic properties and real-time monitoring of gelation processes.
I: Real-Time Characterization of Hydrogel Viscoelastic Properties and Sol-Gel Phase Transitions Using Cantilever Sensors
1. Materials and Methods
1.1 Materials
Example materials can include Alginic acid sodium salt, gelatin (300 g bloom from porcine skin), poly (ethylene glycol) diacrylate (PEGDA) (750 Da), 2,2-Dimethoxy-2-phenylacetophenone (DMPA), calcium chloride, and EDTA, lead zirconate titanate (PZT-5A; 72.4×72.4×0.127 mm3) with nickel electrodes, borosilicate glass, and ethanol (200 proof). The materials also include Polyurethane (Fast-Drying), epoxy (EA 1C-LV) and cyanoacrylate (409 Super Bonder).
1.2 Fabrication of Piezoelectric-Excited Millimeter Cantilever Sensors
Composite PEMC sensors with a flush design can be fabricated from lead zirconate titanate (PZT) as described in previous studies (e.g., Sharma et al. 2011).
1.3 Measurement Principle and Data Acquisition
The sensor resonant frequency (fn), quality factor (Qn), and phase angle at resonance (ϕn), where n indicates the mode number, were continuously monitored with a vector-network analyzer with impedance option (e.g., E5061b-005; Keysight). The sensor's dynamical mechanical response, here, the frequency response, was obtained via electromechanical coupling effects using electrical impedance analysis, which provides electrical impedance magnitude (|Z|) and phase angle (ϕ) spectra of the piezoelectric layer (|Z| and ϕ vs. frequency (f), respectively). While the absolute amplitude of the cantilever vibration could not be determined without additional measurement instrumentation (e.g., associated with optical techniques for deflection measurement), which are challenging in hydrogels, the phase angle of the sensor's electrical circuit at resonance (ϕ=tan−1(ΔV/I)) provides a measure of the relative displacement in the piezoelectric layer and an indirect measure of cantilever amplitude. Thus, the technique is useful for resonant frequency and quality factor tracking in applications that require analysis in complex fluids and materials that may present challenges to the use of optical techniques. Electrical impedance analysis was performed using a stimulus amplitude of e.g., 100 mV AC and zero DC bias across a frequency range (e.g., fn−10 kHz fn fn+10 kHz), which enabled resolution of the off-resonance impedance response and, thus, measurement of the frequency-width-at-half-maximum (FWHM). Sensor signals (fn, ϕn, FWHM, and Qn=fn/FWHM) were acquired using a custom MATLAB program based on continuous monitoring of electrical impedance spectra.
1.4 Hydrogel Preparation
Alginate solutions with various concentrations (e.g., 0.25, 0.5, 0.75, 1, 1.5, and 2.0 wt %) were prepared by dissolving alginic acid sodium salt in deionized water (DIW) at room temperature with continuous stirring. The solutions (e.g., 5 mL) were chemically crosslinked by depositing a droplet (e.g., 500 μL) of saturated calcium chloride on the surface of the polymer solution at a short distance (e.g., approximately 5 mm) from the submerged sensor. Gelatin solutions with various concentrations (e.g., 6, 8, 10, and 12 wt %) were prepared by dissolving gelatin in DIW at 40° C. with continuous stirring. Following dissolution, the solution was maintained at 40° C. until use. PEGDA hydrogels were prepared by dissolving e.g., 1, 2, 3, or 4 g PEGDA in e.g., 18.9, 17.9, 16.9, or 15.9 g of DIW at room temperature, followed by the addition of e.g., 0.1 g of 20 wt % DMPA in ethanol for final solutions containing e.g., 5, 10, 15, and 20 wt % PEGDA with 0.1 wt % DMPA. PEGDA hydrogels were cured with exposure to e.g., 365 nm UV light for 10 minutes (1200 ρW/cm2 at 3 inches; UVGL-58).
1.5 Viscoelastic Property Characterization Using Dynamic-Mode Cantilever Sensors
The shear storage and loss moduli of the surrounding material, here hydrogels, at the sensor's resonant frequency (G′f and G″f, respectively) were calculated based on previously established fluid-structure interaction models for resonant cantilevers (see e.g., Belmiloud et al. 2006, Boskovic et al. 2002, Dufour et al. 2012, Maali et al. 2005, Mather et al. 2012, and Sader et al. 1998). The inertial and dissipative components of the drag force on a vibrating cantilever (g1 and g2, respectively) can be written in terms of the frequency-dependent viscoelastic moduli (G′ and G′) as: (e.g., Mather et al. 2012)
where a1, a2, b1, and b2 are Maali's parameters (e.g., a1=1.0553, a2=3.7997, b1=3.8018, b2=2.7364) (Maali et al. 2005), w is the angular frequency (here, taken as ω=2πfn), ρ is the density of the surrounding material (e.g., fluid), and b is the cantilever width. The components of the drag force can also be calculated from sensor data (i.e., fn and Q) as: (Mather et al. 2012)
where L is the cantilever length, μ=ρcbt is the cantilever mass per unit length, ρc and t are the respective cantilever density and thickness, Q0 and ω0 are the respective quality factor and resonant frequency in the absence of fluid damping (i.e., resonating in vacuum with only internal damping effects present), mc=ρcbtL is the cantilever mass, mA=ρπb2LΓ′/4 is the added mass, Γ′ is the real part of the hydrodynamic function, and ci=mcω0/Q0 is the internal damping coefficient. Due to the scale of the cantilevers (e.g., L=3 mm) the internal damping was not negligible and was subtracted from the measured value (as described in the term ci in Equation 3). In calculation of ci, ω0 and Q0 were approximated as ω0˜2πfn,air and Q0˜Qn,air, which were reasonable assumptions as discussed in the following sections. The hydrodynamic function was approximated using the relation Γ′=a1+a2δ/b, where δ=[(2η/(ρω)]1/2 is the thickness of the thin viscous layer surrounding the cantilever in which the velocity has dropped by a factor of 1/e, and η is the viscosity of the fluid. The solution to the system of equations formed by Equations (1)-(4) provides the viscoelastic properties of the surrounding material based on cantilever sensor data.
1.6 Real-Time Monitoring of Gelation Processes Using Cantilever Sensors
1.6.1 Gelatin Hydrogels: Prior to all experiments, the sensor impedance spectra were characterized in air to obtain the resonant frequency and quality factor. Experiments began by adding e.g., 5 mL of gelatin solution to a dish (e.g., 35 mm) at 40° C. The gelatin solution was maintained at 40° C. during solution phase studies to prevent gelation. The solution was then cooled to room temperature. Subsequently, the cantilever was submerged in the solution to a depth that brought the top surface of the polymer solution 30 μm above the cantilever's anchor. The sensor data acquisition program was subsequently initiated, which enabled continuous monitoring of the sensor signals as the gelatin solution spontaneously underwent a thermoreversible gelation process.
1.6.2 Alginate Hydrogels: The resonant frequency and quality factor in air fn,air and Qair, respectively) were determined as described above. Experiments began by adding 5 mL of room temperature alginate solution to a 35 mm petri dish. The cantilever was then submerged as described in the previous section and data collection was initiated. Following stabilization of the sensor signals, the alginate solutions were chemically crosslinked by manually applying a 500 μL droplet of saturated calcium chloride to the surface of the solution approximately 5 mm from the anchor of the cantilever. Addition of a 500 μL droplet of DIW served as an in situ negative control. Following the stabilization of sensor signals after chemical gelation, the hydrogels were dissolved by applying 3 mL of a 1M aqueous solution of EDTA across the surface of the hydrogel.
1.7 Characterization of Hydrogel Low-frequency Viscoelastic Moduli via Traditional Dynamic Mechanical Analysis Studies
Characterization of hydrogel low-frequency viscoelastic properties was done using a dynamic mechanical analyzer (Q800; TA Instruments). Cylindrical test specimens of alginate and gelatin hydrogels (diameter=12.7 mm and thickness=5 mm) were punched from 5 mm thick hydrogel sheets prepared using the same crosslinking techniques as previously described for the sensor studies. All measurements were acquired by application of a 15 μm periodic displacement at a constant frequency (1 Hz) and 5 mN preload force in the compression mode. Temperature-dependent data for the thermally-responsive gel was acquired under the same conditions using a temperature sweep from 26 to 36° C. at a rate of 0.5° C./min.
1.8 Characterization of Sol-Gel Rheological Properties and Gelation Processes via Traditional Rheology
A rheometer (Discovery DH-2, TA Instruments) was implemented with recessed concentric cylinder geometry. Gelatin solution (8 wt %) was loaded into the test geometry with a 1 mm gap. Testing conditions of 1% strain and 1 Hz were imposed. The sample was held at 40° C. then quenched to 25° C. at a rate of 5° C./min, which mimicked the temperature treatment used in the sensor studies. Data collection began when the sample temperature reached 25° C. and continued for 90 minutes. The time of the gelation process as measured through sensor and rheometer data was normalized by the respective total gelation times. The data was truncated in both sensor and rheometer data to the point where G′ reached 95% of the maximum (G′95) and subsequently normalized by G′95 for comparison.
1.9 Calculation of Limit of Detection
Given that the limit of detection (LOD) is a function of the sensitivity (m) and noise level of the sensor (N), one can use
As shown in
2. Results and Discussion
2.1 Characterization of Cantilever Frequency Response in Concentrated Solutions of Gel-Forming Polymers
As shown in
2.2 Effect of Hydrogel Composition and Low-Frequency Viscoelastic Moduli on Cantilever Frequency Response
Having established that PEMC sensors resonate in concentrated solutions of gel-forming polymers, it was also examined if resonance persisted in gels following the sol-gel phase transition (see
Given that applications may use hydrogels across a range of concentrations, the concentration at which cantilever resonance no longer persisted in the gel phase was also examined (i.e., the concentration at which the cantilever quality factor could not be monitored with suitable resolution for characterization and sensing applications). As shown in
Having established that cantilever resonant frequency and quality factor could be measured across a range of concentrations in various hydrogel systems, the low-frequency viscoelastic moduli (E′ and E′) for each hydrogel examined was characterized to establish the sensor's dynamic range regarding low-frequency viscoelastic moduli sensing. As shown in Table 2 below, a positive correlation was observed among the cantilever quality factor (Qn) and the low-frequency viscoelastic moduli (E′ and E″). Overall, the data in
2.3 Real-Time Monitoring of Gelation Processes Using Millimeter Cantilever Sensors
Having demonstrated that resonance in PEMC sensors persists in hydrogels formed through differing chemistry and that changes in sensor quality factor correlated with low-frequency viscoelastic moduli, it was also of interest to determine if PEMC sensors enable real-time monitoring of sol-gel phase transitions via continuous tracking of sensor signals. Gelatin solutions undergo a thermoreversible sol-gel phase transition at room temperature without the addition of a curing stimulus, resulting in a gel. (Djabourov et al. 1988) As shown in
Similar to the thermoreversible gelation of gelatin solutions, the chemical gelation of alginate solutions can cause exponential decreases in various sensor signals (see
These collective results from the gelatin and alginate hydrogel systems show that in addition to enabling real-time monitoring of the gelation process using resonant frequency, phase angle, and quality factor responses, the sensor responses (specifically, the phase angle and quality factor) enabled the quantification of hydrogel polymer content (i.e., concentration) and low-frequency viscoelastic properties across a wide dynamic range through a calibration approach (i.e., a set of offline DMA measurements taken on experimental standards). Sensor data associated with real-time monitoring of photo-gelation processes is provided in
Having established a sensor-based approach for characterization of sol-gel phase transitions and low-frequency hydrogel viscoelastic properties based on benchmarking (i.e., calibration) of total changes in sensor signals with offline DMA data acquired using traditional techniques, a cantilever fluid-structure interaction model can be used for viscoelastic materials (Equations (1)-(4)) to examine the behavior of the high-frequency storage and loss moduli obtained at the resonant frequency (Gf′ and Gf″, respectively) and understand their correlation with low-frequency moduli (E′ and E″). In other words, this approach can establish the relationship between low-frequency (1 Hz) viscoelastic moduli obtained using traditional characterization platforms (e.g., DMA) and high-frequency viscoelastic moduli (˜35 kHz) obtained using PEMC sensors.
As shown in
In addition to correlation between high- and low-frequency viscoelastic properties in cured hydrogels obtained using sensor-based approaches and traditional platforms, the high- and low-frequency shear moduli exhibited similar temporal responses throughout the gelation process (see
2.5 Modeling of Gelation Process Dynamics Using Sensor Data
Given the previous sections establish that PEMC sensors enable characterization of low- and high-frequency viscoelastic properties and real-time monitoring of gelation processes, the following examines if sensor data could be leveraged to model the dynamics of gelation processes. Sensor responses to chemical gelation of alginate solutions were analyzed using a modified Hill equation based on its previous use in modeling of gelation processes that were characterized using traditional rheological techniques and is given as: (Calvet et al. 2004, Hill 1913)
where Ĝ′ is the normalized storage modulus, t is time, n is the Hill coefficient, and θ is the half-gelation time determined by the time at which G′, and thus, has reached 50% of the total change. The modified Hill equation can also be used to calculate a characteristic gelation rate (P) as:
where G′gel is the storage modulus of the final gel. As shown in
2.6 Real-Time Monitoring of Hydrogel Dissolution Processes
To further evaluate the utility of the sensor for future applications in viscoelastic characterization of hydrogels and continuous monitoring of gelation processes, the following further examines the real-time monitoring of hydrogel dissolution processes. As shown in
Thus, resonance in cantilever sensors persists in hydrogels. This result enables the characterization of low- and high-frequency hydrogel viscoelastic properties and the real-time monitoring of sol-gel phase transitions (i.e., gelation processes). Studies were performed on various hydrogel systems that underwent thermoreversible-, chemical-, and photo-gelation processes. Changes in the sensor phase angle, quality factor, and high-frequency shear moduli obtained at the resonant frequency (G′f and G″f) correlated with low-frequency moduli obtained using traditional DMA and rheology platforms. These results suggest that real-time monitoring of high-frequency viscoelastic moduli using sensor-based approaches provides a promising technique for characterization of gelation dynamics and quantification of viscoelastic properties of hydrogels over a wide frequency range (Hz-kHz). This work also suggests that cantilever sensors could provide a promising platform for sensor-based characterization of hydrogels that may lead to future breakthroughs in process control and high-throughput characterization. In addition, resonance and quality factor tracking in millimeter-scale cantilever sensors appears to provide an attractive integrated characterization and bioanalytical platform for gel-based biomanufactured products, such as molded or 3D bioprinted hydrogel-based tissues, via real-time detection of rheological property changes, chemical sensing, and bio-sensing.
II. Automated High-Throughput Characterization of Viscoelastic Properties and Sol-Gel Phase Transition Diagrams
Materials: As discussed herein, the phase transition behavior and viscoelastic properties of multiple thermoreversible hydrogels based on both synthetic and natural polymers is introduced. This includes hydrogels of Pluronic 127 (molecular weight (MW)=e.g., 12.6 kDa), polyvinyl alcohol (e.g., Pn=500), gelatin (e.g., MW=50-100 kDa, from porcine skin), and methylcellulose (e.g., 4,000 cP at 20° C.). Polymer solutions can be prepared in deionized water (e.g., 18 MQ, Milli-Q System, Millipore). The hydrogels were selected based on their broad utility among a wide range of applications, including engineered tissues, foods, pharmaceuticals, and devices, and because their phase-transition behavior has been previously characterized using alternative low-throughput approaches (see references AMD 2019, Ohkura et al. 1992, Choi et al. 2001, Shibatani et al. 1970, Tanaka et al. 1979, Parker et al. 2012, Bansil et al. 1992, Sanwlani et al. 2011, Takahashi et al. 2001, and Arvidson et al. 2013). Thus, they provide excellent choices for benchmarking the data generated by the new sensor-based HTC platform.
Sensor-based HTC Platform for Terrestrial Environments: As shown in
Hardware: Robot: The HTC platform is based on a three-axis robot structure (e.g., MPS50SL; Aerotech, however any other robotic structure that is capable of positioning the sensor in a three-dimensional space can be used), a digital, a motion controller (e.g., A3200; Aerotech), and a dedicated desktop computer. Stage: Plates are placed on a four-leg mechanical stage that enables manual leveling (e.g., Thorlabs). Leveling can achieved using a 1D laser displacement sensor (e.g., IL-1000; Keyence). A closed-loop controlled thermoelectric cooling module affixed on top of the stage enables heating and cooling of the well plate from 5-80° C. An integrated thermistor and infrared camera ensure temperature sensing on the plate. These components are integrated with a sealed chamber to control disturbances, such as heat transfer caused by natural convection. The chamber can be manually opened by the user to insert and remove well plates. The stage also contains a custom clamping system for well plate anchoring during the measurement to eliminate any potential movement of the plate during measurement and maintain mechanical contact between the bottom of the plate and the thermoelectric cooler. Sensor: Piezoelectric-excited millimeter cantilever (PEMC) sensors with asymmetric anchoring are fabricated from lead zirconate titanate (PZT) chips (5×1×0.127 mm3). Details of fabrication are discussed in references [39]-[45]. Briefly, 30-gauge copper (Cu) wires are soldered to the top and bottom thin-film nickel electrodes at the end of the PZT chip. The chip is then embedded in a 6 mm diameter glass tube with a non-conductive epoxy. Anchor asymmetry is obtained by applying additional epoxy to one side of the cantilever extending from the embedded end. The sensors are then spin-coated with polyurethane (˜30 μm). Subsequently, the sensors are insulated by a chemical vapor deposited parylene-c coating (10 μm) in batches of 25-50 sensors following vendor-supplied protocols (PDS 2010 Labcoter® 2, Specialty Coating Systems, Indianapolis, IN). Data is acquired using an impedance analyzer (E5061B; Keysight). The self-sensing and -exciting design of the PEMC sensor facilitates robust monitoring of gel-based materials analysis (e.g., viscoelastic properties) due to the sensor's flow regime as indicated by a cantilever Reynolds Number (Rec>1) (See, e.g., references Johnson et al. 2011, Looker et al. 2008, and Van Eysden et al. 2009). The sensor also supports dual transduction of viscoelastic property changes through both dynamic mechanical and electromechanical effects (see e.g.,
Experimental Studies: The following terrestrial experimental studies are performed to understand the effect of microgravity on sol-gel phase transition behavior of hydrogels and the high-frequency viscoelastic properties of hydrogels formed in microgravity.
Path Planning for Automated Sensor-based Rheological Property Characterization in Well-Plate Formats: The sensor's path across the well plate, known as the tool path, is defined in terms of robot motion commands using G code. The sensor path is based on a repeated dwell-dip-dwell-move loop that occurs in each well. Measurement of rheological properties occurs during the dwell phase. The measurement occurs at a fixed temperature. The starting temperature is chosen such that the sol-gel system is in the solution phase (5° C. in the Pluronic-F127, polyvinyl alcohol, and methylcellulose hydrogels and 60° C. for the gelatin hydrogels). The sensor path trajectory is in the direction of increasing well number, and here, increasing concentration based on the plate preparation protocol, which is described further in the following section. The stabilization time in air before the dip command is one minute. The dip motion command results in full submersion of the sensor in the material. The second dwell command has a duration of three minutes during which the rheological properties of the material are obtained. A feed rate of 1 mm/s is used for all motion commands to reduce the potential for robot motion to cause vibration of the robot or plate holder and has been verified through our proof-of-concept studies. The measurement is repeated at successively higher or lower temperatures based on the starting temperature using a temperature increment of 3° C. across the 5-60° C. temperature range. The plate lid is closed during all heating and cooling cycles to mitigate the formation of temperature gradients in the well. Sensor data acquisition begins one hour before initiating the previously described tool path to allow the sensor signals to reach a steady state. Sensor data is continuously collected throughout the tool path.
Plate Preparation Protocol: The material systems are prepared in 96-well plates. Sol-gel systems are prepared in the solution phase and mixed for three minutes (ARE-310; Thinky) prior to plate filling to ensure the presence of a homogeneous phase. Following preparation, the mixtures are successively dispensed in the individual wells of the 96-well plate in the order of increasing concentration (see
The wells C0 to CN can be arranged in rows and columns as shown in
Data Acquisition: Sensor data is acquired as described in our previous reports (see e.g., references Mutharasan et al. 2010, Johnson et al. 2011, Sharma et al. 2011, Johnson et al. 2011, Johnson et al. J. Micromech. Microeng, 2011, Johnson et al. Anal. Chem., 2013, and Johnson et al. Analyst, 2013). The sensor impedance and phase angle frequency responses are continuously monitored across a frequency range of ±10 kHz centered on the resonant frequency using a network analyzer (E5061B; Keysight). This approach enables continuous monitoring of the sensor's mechanical and electrical outputs using a dedicated computer, including the resonant frequency (fn=ωn/2π), quality factor (Q=fn/frequency-width-at-half-maximum (FWHM)), impedance at resonance, and phase angle at resonance (see
Data Analysis and Interpretation: As described in the Data Acquisition Section, Matlab provides real-time monitoring of the sensor signals. As shown in
Risk Mitigation—Potential Pitfalls and Alternative Options: Although not observed in our proof-of-concept studies, if concerns arise with the stage-based thermoelectric cooling process, such as large temperature gradients in the material, thermal insulating material (silicone) will be added between the individual wells of the plate to increase the thermal inertia and reduce the rate of heat transfer between the material in the well plate and the surroundings. The CubeLab version of the HTC platform also contains integrated temperature sensing capabilities to ensure uniform heating of well plates (see the Operational Approach Section).
Proof-of-Concept Studies (Preliminary Data): Photographs of the ground version of the sensor-based HTC platform and the associated well-plate measurement format are shown in
As shown in
Given the fact that the concentration of the wells are known a priori, potential effects of mass transfer between adjacent wells during the measurement can be corrected for using the sensor's resonant frequency response which enables quantification of added-mass effects as Δmn=−0.5mnΔfn/fn, where Δfn is the resonant frequency shift, mn is the effective mass of the cantilever for the nth mode, and Δmn is the added mass. A positive correlation can be established between low- and high-frequency viscoelastic properties, ranging from 1 Hz (DMA acquired; Q800; TA Instruments) to ˜100 kHz (sensor acquired). PEMC sensors exhibit resonant modes from 10 kHz to 1.2 MHz, thereby enabling characterization of hydrogel viscoelastic properties over two orders of magnitude.
The process further includes maintaining the position of the senor in the first well 1402 (1712). The controller can maintain the sensor position in the first well to continue to acquire the electrical parameters that can be translated into the material properties of the sample. In some examples, the controller needs to maintain the sensor in the sample for only a time duration that is sufficient for acquiring a reliable reading. Any additional time spent in the first well can be wasteful, and can impact the total time needed for traversing all the wells in the well plate 1402. In some examples, the controller can determine when the retract the sensor based on whether the one or more electrical parameters have reached steady state value (1714). In one approach, the controller can determine a derivative, over a time window, of the one or more electrical parameters. The derivative can indicate the rate of change of the value of the electrical parameter. If the rate of change is below a threshold value, the controller can determine that the one or more electrical parameters has reached steady state. The threshold value can be determined experimentally and can include a value of rate of change that corresponds to a time in the well that provides readings at desired reliability. Once the controller determines that the one or more electrical parameters have reached steady state, the controller can instruct the robotic system to retract the sensor from the first well 1402 (1716). Traditional systems may set a fixed amount of time for which the sensor is immersed into the wells to measure the values of the electrical parameters. This, however, can cause an increase in the time per cell needed to capture the values of the electrical parameters, as the sensor may spend more time than that needed to capture reliable values from the sample. In contrast, the controller controls the sensor to remain in the sample for only as long as reliable values can be captured, and then retracts the sensor to move on to the next sensor. As a result, the time spent per cell to is reduced. In instances where the well plate include dozens of samples, even incremental decrease in per cell time can translate into large time savings and efficiency in characterizing the dozens of samples.
The controller, can store the time instance at which the retract instructions are sent as a time stamp at which the one or more electrical parameters can be used to characterize the sample within the first well. The controller after retracting the sensor from the first well 1402, can position the sensor over the second well 1404 and carry out the same process discussed above to lower and then retract the sensor from the second well 1404. In this manner, the controller can lower the sensor to capture values of the electrical parameters of the plurality of samples in the well plate.
In some example, the effectiveness of the sensor to measure the electrical properties of the samples can be diminished because of the adherence of the sample on the sensor. For example, the sensor after being immersed in one or more sample fluids can have some quantities of the sample fluid adhered onto the sensor. As a result, when the senor is immersed into a different sample, the previous sample adhered onto the sensor may affect or alter the readings for the current sample. Thus, the controller can occasionally immerse the sensor into a washing fluid, such as water, to wash off the samples from the surface of the sensor. In one example, the controller can immerse the sensor in a well that includes water between any two samples. In some instances, the controller can immerse the sensor in the washing fluid after taking readings in two or more samples. In some instances, the well plate can be filled with the washing fluid in appropriate wells along the sensor path 1408 such that the frequency at which the controller washes the sensor is predetermined. In some instances, the controller can dynamically determine when the sensor needs washing. For example, the controller can measure the values of the one or more electrical parameters of the sensor to determine whether the sensor needs washing. In some examples, the controller can measure the values of the one or more electrical parameters when the sensor is completely retracted from the sample and is assumed to be in air. If the value of the one or more electrical parameter is below a threshold value, the controller can determine that the sensor needs cleaning. The threshold value can be experimentally determined by adhering to the sensor to several quantities of sample substance and determining the corresponding values of the electrical parameters. The value below which the sensor does not provide reliable readings can be set as the threshold value. Once the controller determines that the value of the one or more electrical parameters is below the threshold value, the controller can refrain from immersing the sensor into another well containing a sample in the sensor path, but instead move the sensor over any of one or more wells that include a washing fluid and immerse the sensor in the washing fluid. The controller can immerse the sensor in the washing fluid for a predetermined time that is sufficient for cleaning the sensor or can monitor the electrical parameters and determine the time required for cleaning based on the instantaneous values of the electrical parameters. Once the sensor is cleaned, the controller can then resume the sensor path 1408 from its last position in the sensor path 1408 and continue to characterize samples in the well until the last sample has been characterized.
The approaches discussed above can be used for determining material properties of samples, and not just rheological properties. In particular, the approaches above can be used to determine physical properties (e.g., density, dielectric properties, etc.), mechanical properties (e.g., rheological properties), and molecular properties (e.g., binding constants), and structural data related to the samples. As an example, Campbell and Muthurasan (Detection and quantification of proteins using self-excited PZT-glass millimeter-sized cantilever, Biosensors and Bioelectronics 21 (2005), 597-607) discuss deriving molecular properties of a sample from the electrical parameters measured by the sensor when immersed in the sample. For example, the electrical parameters can be used to determine a binding reaction rate constant associated with proteins in the sample. One feature of the sensor discussed herein is that its resonant frequency is dependent on its mass. The controller can measure this resonant frequency in the sample while protein reacts or binds with the sensing glass cantilever surface. In some other instances, the approach discussed above also can be used to determine thermodynamic parameters associated with the binding reaction such as, for example, the entropy and enthalpy. Johnson and Muthurasan (pH Effect on Protein G Orientation on Gold Surfaces and Characterization of Adsorption Thermodynamics, ACS Journal of Surfaces and Colloids, 18 Apr. 2012, 28(17): 6928-6934) in equation 3 deriving the enthalpy based on resonance frequency shifts of a sensor in a sample. Thus, the above approach can be utilized to make high throughput characterizations of not only the physical and mechanical properties, but also molecular properties of a large set of samples.
Implementations of the subject matter and the operations described in this specification can be implemented in digital electronic circuitry, or in computer software embodied on a tangible medium, firmware, or hardware, including the structures disclosed in this specification and their structural equivalents, or in combinations of one or more of them. Implementations of the subject matter described in this specification can be implemented as one or more computer programs, i.e., one or more components of computer program instructions, encoded on computer storage medium for execution by, or to control the operation of, data processing apparatus. The program instructions can be encoded on an artificially-generated propagated signal, e.g., a machine-generated electrical, optical, or electromagnetic signal that is generated to encode information for transmission to suitable receiver apparatus for execution by a data processing apparatus. A computer storage medium can be, or be included in, a computer-readable storage device, a computer-readable storage substrate, a random or serial access memory array or device, or a combination of one or more of them. Moreover, while a computer storage medium is not a propagated signal, a computer storage medium can include a source or destination of computer program instructions encoded in an artificially-generated propagated signal. The computer storage medium can also be, or be included in, one or more separate physical components or media (e.g., multiple CDs, disks, or other storage devices).
It should be emphasized that the above-described embodiments of the present disclosure are merely possible examples of implementations, and are set forth only for a clear understanding of the principles of the disclosure. Many variations and modifications may be made to the above-described embodiments of the disclosure without departing substantially from the spirit and principles of the disclosure. All such modifications and variations are intended to be included herein within the scope of this disclosure.
References: All cited references, patent or literature, are incorporated by reference in their entirety. The examples disclosed herein are illustrative and not limiting in nature. Details disclosed with respect to the methods described herein included in one example or embodiment may be applied to other examples and embodiments. Any aspect of the present disclosure that has been described herein may be disclaimed, i.e., exclude from the claimed subject matter whether by proviso or otherwise.
This application claims priority to U.S. Provisional Patent Application No. 63/010,621, entitled “SENSOR-BASED HIGH-THROUGHPUT CHARACTERIZATION RHEOLOGY PLATFORM AND METHODS OF USE THEREOF,” filed Apr. 15, 2020, the entirety of which is incorporated by reference herein.
This invention was made with government support under award 1739318 awarded by the National Science Foundation. The government has certain rights in the invention.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2021/027521 | 4/15/2021 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 63010621 | Apr 2020 | US |
