- Mechanics of fibrous assemblies
- Electronic Textiles or E-textiles (Fiber/Textile based electrical devices)
- Electroactive polymers
- Design and analysis of technical textiles
- Technology of fabric formation, in particular, weaving technology
Examples of Recently Completed and Current Research Projects:
Functionally Tailored Textiles: 3-D Structures Through Melt Blown Technology: The research is aimed at developing appropriate technology necessary to produce three-dimensional molded garments to produce low-cost combat uniforms with effective barrier characteristics, using minimal joining. The system being developed is called Robotic Fiber Assembly and Control (RFAC) system. RFAC system will allow the incorporation of fibers, powders, or other appropriate additives into the garment systems. The additives may identify, measure, absorb, and/or deactivate chemical/biological agents. In the RFAC system deposition of melt-blown fibers on an appropriate mold is controlled by a six-axis industrial robot. The system allows precise control of fiber orientation distribution, fiber diameter distributions, and pore size distribution.
Woven Fabric-based Electrical Circuits (Electro-textiles): Fabric-based electrical circuits are fundamental to electronic textile products of the future. The objective of the current research is to develop fabric-based electrical circuits by interlacing conducting and non-conducting threads into woven textile structures for civilians as well as military applications. Wired interconnections between different devices attached to the conducting elements of these circuits are made by weaving conductive threads so that they follow desired electrical circuit designs. In a woven electrically conductive network, routing of electrical signals is achieved by the formation of effective electrical interconnects and disconnects. Resistance welding is identified as one of the most effective means of producing crossover point interconnects and disconnects. These circuits are evaluated for signal integrity issues (crosstalk, etc.). Two new thread structures – coaxial and twisted Pair copper threads to minimize cross talk have been developed and evaluated. Significant reductions in crosstalk were obtained with the coaxial and twisted pair thread structures when compared with bare copper thread or insulated conductive threads.
Development of Fiber Actuators: Fiber actuators are capable of dimensional change under the applied electrical field. Dielectric elastomer-based prototype fiber actuators have been developed using commercially available dielectric elastomer tubes and by applying appropriate compliant electrodes to the inner cavity and outer walls of these tubes. The force and displacement generated by such actuators have been studied under different isometric conditions and as a function of the applied electric field. The actuation characteristics such as axial strains, radial strains, and actuation blocking forces produced in the prototype upon actuation were studied. Actuation strain and blocking force are strongly influenced by the applied prestrain and have a parabolic relationship to the applied electric field. High actuation strains (>50%) are currently afforded by dielectric elastomers at relatively high electric fields (>50 V/µm). A new class of electroactive polymers, suitable for fiber formation, have been developed by incorporating low-volatility, aliphatic-rich solvent into a nanostructured triblock copolymer yielding physically crosslinked micellar networks that exhibit excellent displacement under an external electric field. Ultrahigh areal actuation strains (>200%) at significantly reduced electric fields (<40 V/µm) has been achieved.
Electroactive Nanostructured Polymers as Tunable Actuators: Lightweight and conformable electroactive actuators stimulated by acceptably low electric fields are required for emergent technologies such as micro-robotics, flat-panel speakers, micro air vehicles and responsive prosthetics.1,2 High actuation strains (>50%) are currently afforded by dielectric elastomers at relatively high electric fields (>50 V/µm). In this work, we have developed a nanostructured copolymer blend that yields a physically cross-linked micellar network and exhibits excellent displacement under an external electric field. Such property development reflects reductions in matrix viscosity and nanostructural order, accompanied by an enhanced response of highly polarizable groups to the applied electric field. These synergistic property changes result in ultrahigh areal actuation strains (>200%) at significantly reduced electric fields (<40 V/µm). The use of nanostructured polymers whose properties can be broadly tailored by varying copolymer characteristics or blend composition represents an innovative and tunable avenue to reduced-field actuation for advanced engineering, biomimetic and biomedical applications.
Design, Characterization, and Processing of Carbon Nanofiber-Modified PVC as Fabric Sensor Composites for E-Textiles: The research aims to use screen-printing to fabricate an elastic and conductive nanocomposite layer of Plastisol, plasticized poly(vinyl chloride) (PVC), and carbon nanofiber (CNF) on textile fabrics to produce a piezoresistive strain-sensing substrate. The fabric sensor composite (FSC) being developed is based on the hypothesis that an elastomeric layer containing conducting nanoparticles printed on fabric substrates can yield a flexible, piezoresistive coating that can be tailored for specific applications. The research marries the demonstrated utility of plastisol as a print medium with the novelty of CNF-based polymer nanocomposites as applied to FSCs designed for use in electronic textiles. Previous studies have repeatedly identified benefits of CNFs relative to their CNT analogs, but relatively few studies have focused on conformable nanocomposites containing CNFs. The work seeks to establish a fundamental understanding of the physical factors governing CNF dispersion, percolation and subsequent mobility (upon drying) in a solvated polymer system (plastisol print medium) as a necessary prerequisite to the rational development of the target FSC. Insight into the percolation behavior of CNFs embedded in plastisol and subsequent property evolution will help to elucidate and further optimize the piezoresistive behavior of the FSC. Thus far, the percolation threshold of the plastisol-CNF was observed to be at ~2wt% and that the concentration of CNF where the resistivity starts to saturate is observed to be at 5wt%. Another significant observation is the increase of about 8 orders of magnitude in the conductivity of the composite when the concentration of the CNF was increased from 2wt % to 5wt %.
- TT 351 – Woven Fabric Technology ,
- TT 331 – Performance Evaluation of Textile Materials ,
- TT 581 – Technical Textiles ,
PhD Fiber and Polymer Science North Carolina State University
MS Textile Materials and Management North Carolina State University
M Tech Textile Engineering Indian Institute of Technology
BSc Tech Textile Technology University of Calcutta
Area(s) of Expertise
- Bioinspired Structures for Soft Actuators , ADVANCED MATERIALS TECHNOLOGIES (2022)
- Bioinspired Bistable Dielectric Elastomer Actuators: Programmable Shapes and Application as Binary Valves , SOFT ROBOTICS (2021)
- Melt-Extruded Sensory Fibers for Electronic Textiles , MACROMOLECULAR MATERIALS AND ENGINEERING (2021)
- Skin-Inspired Capacitive Stress Sensor with Large Dynamic Range via Bilayer Liquid Metal Elastomers , ADVANCED MATERIALS TECHNOLOGIES (2021)
- Textile-Based Pressure Sensors for Monitoring Prosthetic-Socket Interfaces , IEEE SENSORS JOURNAL (2021)
- Thermoelectric Materials for Textile Applications , MOLECULES (2021)
- 3D Printing of Textiles: Potential Roadmap to Printing with Fibers , Advanced Materials (2020)
- Form-stable phase-change elastomer gels derived from thermoplastic elastomer copolyesters swollen with fatty acids , THERMOCHIMICA ACTA (2020)
- Fully‐Textile Seam‐Line Sensors for Facile Textile Integration and Tunable Multi‐Modal Sensing of Pressure, Humidity, and Wetness , Advanced Materials Technologies (2020)
- In-Plane Thermoelectric Properties of Flexible and Room-Temperature-Doped Carbon Nanotube Films , ACS Applied Energy Materials (2020)
This proposal aims at solving a long-standing problem in the field of prosthetics ÃƒÂ¢Ã¢â€šÂ¬Ã¢â‚¬Å“lack of inner-socket sensor technology. Due to this limitation, monitoring the inner socket environment (such as socket pressure, moisture, and temperature) is impossible. The proposed textile based multimodal sensor interface will be evaluated in real-time inner socket environment monitoring to enable self-management.
Textiles constitute an obvious choice as multifunctional platforms, since they are worn and used to cover and drape over many of the surfaces around us. They are commonly used to provide protection in hostile environments. The present work proposes a systematic investigation into sensory characteristics of textile structures assembled from multicomponent fibers to produce fiber-based sensory textiles that are capable of generating measurable electrical response under various stimuli.
EMN-14-F-S-06 Phase-Change Gels Designed for Laminated Products for Use in Home and Office Settings Phase change materials (PCMs) constitute a broad class of chemical compounds that typically undergo a first-order phase transition (e.g., melting/freezing or evaporation/ condensation) at a temperature that lies near a target value for a given application. Associated with this thermodynamically-reversible transition is a latent heat that must be overcome before a rise or fall in temperature proceeds. In this fashion, the PCM can be used effectively to extract heat from (and thus cool) a warm body or provide heat to a cool body. For illustrative purposes, consider a PCM that is heated from a temperature below its transition temperature. Initially, the temperature of the PCM increases according to its heat capacity, which is a material property that relates a change in heat to the corresponding change in temperature. Once the PCM reaches its transition temperature, however, it remains isothermal until it fully undergoes its phase transition. Beyond this temperature, the PCM continues to change temperature with a new, higher heat capacity. This series of events is schematically depicted in Figure 1. As is evident from this heating scenario, an effective PCM must possess (1) a target-specific transition temperature, (2) a relatively high latent heat to absorb/emit heat under isothermal conditions, and (3) relatively high heat capacities to absorb heat without changing temperature significantly above and below the transition temperature. Another consideration is the extent of thermal expansion at temperatures lower than and above the thermal transition, as well as at the transition itself. For this reason, while high latent heats can be best achieved with PCMs designed to possess an evaporation/condensation transition, the associated volume increase and likelihood of losing PCM vapor from a reusable thermal comfort system preclude such materials from further consideration. Challenges in the use of PCMs that activate upon melting/freezing include incorporating the mass required to achieve adequate performance under target conditions, heat transfer limitations and the degree of cooling required to induce freezing (along with crystallization kinetics). To avoid complications due to melting of the PCM, we intend to use a technology derived from thermoplastic elastomers wherein the PCM is incorporated into the matrix of the TPE. In this manner, melting of the PCM results in a thermodynamically stable gel that does not flow. To improve heat transfer, the PCMs will be modified with thermally conductive nanoparticles at concentrations above the percolation threshold to expedite thermal conduction. For this reason, we refer to these hybrid nanomaterials as Phase-Change Elastomer Nanocomposites (PCENs). Promising and economically viable conductive nanoparticles for use in this design include high-aspect-ratio silver nanowires, which tend to possess relatively low percolation thresholds (ca. 1 wt%). Analysis of these materials sandwiched between polymers of interest to Eastman (e.g., Tritan) will be conducted to ascertain the cooling/heating efficiency of such laminates for use in homes and/or automobiles.
Abstract: As a natural interface between humans and the environment in which we live, textiles offer tremendous surface area to functionalize and deploy sensors, actuators, and other devices ubiquitously and in relatively lower production costs to allow for electronic sensory textiles to enable novel cyber-physical systems towards Internet of Things. We have developed a strategically designed textile structure, assembled from co-extruded multicomponent fibers (CoMFi), to produce Fabric-based Integrated Sensing Technology (FIrST) that is capable of generating useful electrical response under various stimuli. The unique structural and material characteristics of CoMFi integrates sensing elements into the structure of the textile for concurrent real-time monitoring of biopotentials, tactile forces, moisture, temperature, hydration and detection of analytes in bodily fluids such as urine or sweat.
The objectives of this project are to: 1. Develop a portable pneumatic splicing system for heavy denier continuous filament yarns 2. Optimize the pneumatic splice configuration that provide the least structure changes of woven fabricÃƒÂ¢Ã¢â€šÂ¬Ã†â€™
Fiber actuators are capable of changing their dimensions (length, diameter etc) as well as generate a force when activated using appropriate electric field. Our objective is to fabricate fiber actuators from electroactive polymers, specifically dielectric elastomers. Through appropriate experimental design and theoretical analysis we plan to understand the critical parameters in the design of the fiber actuator. For the analysis we plan on using finite element modeling (using ABAQUS) of the deformation of the actuator under electrostatic stress.
Polymeric nanocomposites that are filled with conducting nanoparticles have attracted considerable scientific and commercial interest in recent years because of their wide ranging potential and availability as new functional materials. The objective of the proposed research is to fabricate lightweight, conformable sensory materials that are compatible with electronic textile products including body-worn sensors. The proposal aims to use screen-printing to fabricate an elastic and conductive nanocomposite layer of plastisol, plasticized poly(vinyl chloride) (PVC), and carbon nanofiber (CNF) on existing textile fabrics to produce a piezoresistive strain-sensing fabric. Our overarching objective of developing a fabric sensor composite (FSC) is based on the hypothesis that an elastomeric layer containing conducting nanoparticles printed on fabric substrates can yield a flexible, piezoresistive coating that can be tailored for specific applications. The objective is also based on the premise that lightweight sensory materials can be produced by controlling the volume fraction of CNF relative to the percolation threshold at which the insulating polymer layer transitions into a conducting medium. The novelty of the proposed research lies in the use of PVC in the form of plastisol and CNF. Plastisol is a commercially available dispersion of PVC resin in a plasticizer that provides unique and tunable print properties. Fractionated CNFs, on the other hand, are well-suited to the fabrication of FSCs since they are more easily dispersed, less expensive and less rigid than their carbon nanotube (CNT) analogs. In addition, the proposed method of application, screen-printing, is a well understood process that can be readily adapted to the general development of conformable self-monitoring systems and, more specifically, FSCs. The scope of the project proposed here includes the following: (1) dispersion of CNFs in plasticized PVC by reported and novel methods, (2) characterization of CNF/PVC nanocomposites varying in CNF diameter, aspect ratio, concentration and dispersion route to determine the percolation threshold and piezoresistive response, (3) application and drying of the CNF/PVC nanocomposites on fabric surfaces to determine adhesion, wettability and electro-mechanical properties, and (4) examination of the resultant FSCs by advanced microscopy methods to elucidate the distribution and orientation of the CNFs under the same conditions listed in (2).
The objective of the proposed research is to fabricate fiber actuators from electroactive polymers, specifically, dielectric elastomers (DE) using multi-component fiber extrusion technologies. The ?fiber actuators? are fibers that are capable of changing their dimensions (length, diameter, etc.) as well as generate a force when activated using appropriate electrical field. Muscle-like fiber actuators capable of mimicking biological muscles have many potential applications including medical assist devices, and next generation humanoid robots. In textiles, the fibers can be used for porosity control and fabric bulk control among many other potential applications. The work is motivated by successful demonstration of the concept in a recently completed limited study and the simplicity of the principle of working of DE actuators as well as the tremendous potential offered by the current fiber forming technologies to fabricate these.
An integrated, low-cost Braille reader will be developed using micromachining techniques and polymer actuator technologies.
The proposed research is to adapt various preparatory and weaving technologies to weave carbon nanotube (CNT) yarns. The challenge is to develop an optimal process to weave very thin CNT yarns (ca. 2.8 tex) along both warp and filling to form a fabric.