This Small Business Technology Transfer Phase I project seeks to develop a flexible, pressure-sensitive membrane comprising chemically functionalized multiwalled carbon nanotubes (f-MWCNTs) to address several issues that hamper the use of existing piezoresistive membrane materials: a) interfacial integrity, b) fatigue life related to the number of pressure application cycles, and c) cost effectiveness. A piezocomposite sensor converts mechanical energy into an electrical signal and shows reversibility of electromechanical response in the elastic region of deformation. Commercial piezoresistive composites based on lead zirconia titanate (PZT) or metallic fillers lack reliability over time because of brittleness and poor adhesion to the substrate. Piezoresistive composites incorporating conductive carbon black suffer from nonlinearity, non-uniformity, hysteresis and limited sensor life. While use of f-MWCNTs to form the conductive network will enable piezo-resistive behavior, their use will also convey multifunctional aspects to the membrane: improved fatigue life, physical strength, and thermal conductivity (reducing heat buildup that contributes to fatigue). The Phase I project will tackle the initial development phase of a piezo-resistive nanocomposite (PZ-NC) elastomeric membrane incorporating homogeneously dispersed f-MWCNTs as the conductive element. Ultimately, the PZ-NC membrane thus developed will be integrated into a Schottky diode array element for repetitive use, large-area pressure sensors. The broader impact/commercial potential of this project extends to several distinct market verticals. Modern biometric analysis, such as fingerprinting, is accomplished with digital scanners, where images can be distorted by sweat or excess pressure. Alternatively, pressure sensitive membranes can be used for fingerprinting where a load of 0-5 N results in a significant change in resistance of the membrane. For this type of application the increase in horizontal conductivity with pressure and the gradient response of the conductivity are vital. The proposed technology of PZ-NC, if successful, will address these issues, and will significantly improve the accuracy of the latter technology, for example by lowering the False Acceptance Rate (FAR). Furthermore, elastomer seals and gaskets are routinely used in oil and gas operations. The ability to quickly and accurately measure pressure on sealing elements in difficult-to-reach locations is a critical and currently underserved need. Pressure sensitive seals, comprising PZ-NC materials such as those proposed herein, could relay pressure changes or overpressure conditions, giving operators an indication of impending danger or of required maintenance.
