Dr. Stephen A. Sarles Profile

Dr. Stephen A. Sarles

Assistant Professor at Univ of Tennessee

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Publications (14)

Proceedings Article | 8 May 2014 Paper

Role of the array geometry in multi-bilayer hair cell sensors

Nima Tamaddoni, Stephen Sarles

Proceedings Volume 9055, 90550D (2014) https://doi.org/10.1117/12.2045377

KEYWORDS: Sensors, Electrodes, Capacitance, Interfaces, Amplifiers, Biomimetics, Brain, Ear, Ion channels, Molecules

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Recently, a bio-inspired, synthetic membrane-based hair cell sensor was fabricated and characterized. This sensor generates current in response to mechanical stimuli, such as airflow or free vibration, which perturb the sensor’s hair. Vibration transferred from the hair to a lipid membrane (lipid bilayer) causes a voltage-dependent time rate of change in electrical capacitance of the membrane, which produces measurable current. Studies to date have been performed on systems containing only two droplets and a single bilayer, even though an array of multiple bilayers can be formed with more than 2 droplets. Thus, it is yet to be determined how multiple lipid bilayers affect the sensing response of a membrane-based hair cell sensor. In this work, we assemble serial droplet arrays with more than 1 bilayer to experimentally study the current generated by each membrane in response to perturbation of a single hair element. Two serial array configurations are studied: The first consists of a serial array of 3 bilayers formed using 4 droplets with the hair positioned in an end droplet. The second configuration consists of 3 droplets and 2 bilayers in series with the hair positioned in the central droplet. In serial arrays of up to four droplets, we observe that mechanotransduction of the hair’s motion into a capacitive current occurs at every membrane, with bilayers positioned adjacent to the droplet containing the hair generating the largest sensing current. The measured currents suggest the total current generated by all bilayers in a 4-droplet, 3-bilaye array is greater than the current produced by a single-membrane sensor and similar in magnitude to the sum of currents output by 3, single-bilayer sensors operated independently. Moreover, we learned that bilayers positioned on the same side of the hair produce sensing currents that are in-phase, whereas bilayers positioned on opposite sides of the droplet containing the hair generate out-of-phase responses.

Proceedings Article | 4 April 2012 Paper

Formation, encapsulation, and validation of membrane-based artificial hair cell sensors

Kevin Garrison, Stephen Sarles, Donald Leo

Proceedings Volume 8339, 83390B (2012) https://doi.org/10.1117/12.915172

KEYWORDS: Sensors, Ear, Data acquisition, Infrared sensors, Analytical research, Capacitance, Surface conduction electron emitter displays, Ions, Electrodes, Aluminum

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Proceedings Article | 4 April 2012 Paper

Fabricating neuromast-inspired gel structures for membrane-based hair cell sensing

Nima Tamaddoni, Christopher Stephens, S. Sarles

Proceedings Volume 8339, 833908 (2012) https://doi.org/10.1117/12.915203

KEYWORDS: Sensors, Interfaces, Neodymium, Electroluminescence, Polymers, Ultraviolet radiation, Mechanical sensors, Microelectromechanical systems, Electrodes, Laser induced plasma spectroscopy

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Proceedings Article | 4 April 2012 Paper

Study of the effects of ionic liquids on lipid bilayers

Taylor Young, Stephen Sarles, Tianyu Wu, Matthew Green, Timothy Long, Donald Leo

Proceedings Volume 8339, 833906 (2012) https://doi.org/10.1117/12.915078

KEYWORDS: Liquids, Electrodes, Interfaces, Capacitance, Ions, Sensors, Ultraviolet radiation, Water, Chemistry, Microscopes

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Proceedings Article | 4 April 2012 Paper

A bio-inspired aquatic flow sensor using an artificial cell membrane

Preston Pinto, Kevin Garrison, Donald Leo, Stephen Sarles

Proceedings Volume 8339, 833907 (2012) https://doi.org/10.1117/12.915198

KEYWORDS: Sensors, Biomimetics, Skin, Polyurethane, Interfaces, Receptors, Aluminum, Electrodes, Control systems, Organisms

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Proceedings Article | 29 March 2011 Paper

Cell-inspired electroactive polymer materials incorporating biomolecular materials

Stephen Sarles, Donald Leo

Proceedings Volume 7976, 797626 (2011) https://doi.org/10.1117/12.881703

KEYWORDS: Interfaces, Capacitance, Solids, Polymers, Resistance, Electroactive polymers, Molecules, Sensing systems, Molecular biology, Proteins

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Proceedings Article | 23 March 2011 Paper

Hair cell sensing with encapsulated interface bilayers

Stephen Sarles, Donald Leo

Proceedings Volume 7975, 797509 (2011) https://doi.org/10.1117/12.880571

KEYWORDS: Capacitance, Interfaces, Sensors, Motion measurement, Electrodes, Video, Polyurethane, Liquids, Resistance, Molecules

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Proceedings Article | 12 April 2010 Paper

Physical encapsulation and controlled assembly of lipid bilayers within flexible substrates

Stephen Sarles, Donald Leo

Proceedings Volume 7643, 764321 (2010) https://doi.org/10.1117/12.847751

KEYWORDS: Interfaces, Silicon, Semiconducting wafers, Proteins, Capacitance, Electrodes, Plasma, Microfluidics, Molecules, Molecular self-assembly

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Proceedings Article | 7 April 2009 Paper

Incorporation and characterization of biological molecules in droplet-interface bilayer networks for novel active systems

Stephen Sarles, Pegah Ghanbari Bavarsad, Donald Leo

Proceedings Volume 7288, 72880H (2009) https://doi.org/10.1117/12.815846

KEYWORDS: Proteins, Interfaces, Resistance, Molecules, Molecular biology, Molecular self-assembly, Ions, Dielectric spectroscopy, Electrodes, Electrical breakdown

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Proceedings Article | 18 April 2008 Paper

Characterization of porous substrates for biochemical energy conversion devices

Vishnu Baba Sundaresan, Stephen Andrew Sarles, Donald Leo

Proceedings Volume 6928, 69280K (2008) https://doi.org/10.1117/12.776328

KEYWORDS: Silicon, Proteins, Coating, Molecules, Capacitance, Microelectromechanical systems, Resistance, Capacitors, Prototyping, Dielectric spectroscopy

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Proceedings Article | 10 April 2008 Paper

Optimization of active electrodes for novel ionomer-based ionic polymer transducers

Andrew Duncan, Stephen Sarles, Donald Leo, Timothy Long, Barbar Akle, Matthew Bennett

Proceedings Volume 6927, 69271Q (2008) https://doi.org/10.1117/12.776575

KEYWORDS: Electrodes, Data modeling, Resistance, Particles, Transducers, Circuit switching, Polymers, Liquids, Interfaces, Electromechanical design

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Proceedings Article | 11 October 2007 Paper

Study of supported bilayer lipid membranes for use in chemo-electric energy conversion via active proton transport

Stephen Sarles, Vishnu Sundaresan, Donald Leo

Proceedings Volume 6769, 67690N (2007) https://doi.org/10.1117/12.734001

KEYWORDS: Resistance, Proteins, Acquisition tracking and pointing, Electrodes, Signal processing, Biological research, Ions, Molecules, Resistors, Sensors

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Bilayer lipid membranes (BLMs) have been studied extensively due to functional and structural similarities to cell membranes, fostering research to understand ion-channel protein functions, measure bilayer mechanical properties, and identify self-assembly mechanisms. BLMs have traditionally been formed across single pores in substrates such as PTFE (Teflon). The incorporation of ion-channel proteins into the lipid bilayer enables the selective transfer of ions and fluid through the BLM. Processes of this nature have led to the measurement of ion current flowing across the lipid membrane and have been used to develop sensors that signal the presence of a particular reactant (glucose, urea, penicillin), improve drug recognition in cells, and develop materials capable of creating chemical energy from light. Recent research at Virginia Tech has shown that the incorporation of proton transporters in a supported BLM formed across an array of pores can convert chemical energy available in the adenosine triphosphate (ATP) into electricity. Experimental results from this work show that the system-named Biocell-is capable of developing 2µW/cm² of membrane area with 15μl of ATPase. Efforts to increase the power output and conversion efficiency of this process while moving toward a packaged device present a unique engineering problem. The bilayer, as host to the active proton transporters, must therefore be formed evenly across a porous substrate, remain stable and yet fluid-like for protein interaction, and exhibit a large seal resistance. This article presents the ongoing work to characterize the Biocell using impedance analysis. Electrical impedance spectroscopy (EIS) is used to study the effect of adding ATPase proteins to POPS:POPE bilayer lipid membranes and correlate structural changes evident in the impedance data to the energy-conversion capability of various partial and whole Biocell assemblies. The specific membrane resistance of a pure BLM drops from 40-120kΩ•cm² to only a few hundred Ω•cm² upon reconstitution of ATPase proteins. Power characterization indicates that ATP hydrolysis may result in charging of the silver-silver chloride electrodes.

Proceedings Article | 27 April 2007 Paper

Chemoelectrical energy conversion of adenosine triphosphate

Vishnu Baba Sundaresan, Stephen Andrew Sarles, Donald Leo

Proceedings Volume 6525, 65250P (2007) https://doi.org/10.1117/12.715715

KEYWORDS: Acquisition tracking and pointing, Electrodes, Proteins, Resistance, Ions, Prototyping, Capacitance, Sodium, Plasma, Potassium

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Proceedings Article | 5 April 2006 Paper

Active rigidization of carbon-fiber reinforced polymer composites for ultra-lightweight space structures

Stephen Sarles, Donald Leo

Proceedings Volume 6173, 617316 (2006) https://doi.org/10.1117/12.658474

KEYWORDS: Composites, Temperature metrology, Carbon, Polymers, Feedback control, Fiber coatings, Particles, Control systems, Glasses, Thermal analysis

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An active approach for initiating rigidization in carbon-fiber reinforced polymer (CFRP) thermosets links controllable mechanical stiffening to inherent electrical resistivity. With direct applications toward the rigidization of ultra-lightweight, inflatable space structures, temperature-controlled resistive heating is used to create oncommand rigidization. As required by the on-orbit conditions in space, flexible, rigidizable structures demand stable and space-survivable materials that incorporate techniques for providing shape control and structural stiffening. Methods currently employed to achieve a mechanical hardening include many passive techniques: UV curing, sub-T_g hardening, and hydro-gel evaporation. The benefits of a passive system (simplicity, energy efficiency) are offset by their inherent lack of control, which can lead to long curing times and weak spots due to uneven curing. In efforts to significantly reduce the transition time of the composite from a structurally-vulnerable state to a fully-rigidized shape and to increase control of the curing process, an active approach is taken. Specifically, temperature-controlled internal resistive heating initiates thermoset curing in a coated carbon fiber composite to form an electrically-controlled, thermally-activated material. Through controlled heating, this research examines how selective temperature control can be used to prescribe matrix consolidation and material rigidization on two different thermosetting resins, U-Nyte Set 201A and 201B. Feedback temperature control, based on a PID control algorithm, was applied to the process of resistive heating. Precise temperature tracking (less than 1.1°C RMS or ±3.3% error) was achieved for controlled sample heating. Using samples of the thermoset-coated carbon-fiber tow, composite hardening through resistive heating occurred in 24 minutes and required roughly 1 W-hr/inch of electrical energy. The rigidized material was measured to be 14-21 times stiffer in bending than the uncured material. In addition, the cure completion of the resin was measured through differential scanning calorimetry (DSC).

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