A Biocompatible Pressure Sensor Based on Styrene-Isobutylene-Styrene (SIBS) and Carbon Black

摘要

The effect of carbon black (CB) loading percentage on the pressure-sensingcapability of a thermoplastic elastomer (SIBS) composite was investigated. SIBS iswell-known for its excellent biocompatibility and lack of foreign body reaction duringin vivo use. As such, the goal of this effort is the exploitation of this characteristic todevelop implantable and/or external (stick-to-skin) pressure sensors. This studyrepresents an initial analysis of sensing performance as a function of carbon blackcontent; a necessary step toward probing the interaction between the competing designgoals of retained biocompatibility, suitable mechanical strength, flexibility, andsufficient carbon black content to meet or exceed the percolation threshold as requiredfor sensor functionality. The SIBS/CB composites were manufactured throughsolution casting in toluene and a combination of high-shear mixing andultrasonication. The dependence on carbon black content and optimum carbon loadingfor pressure sensing applications was determined for these composites by measuringthe change in voltage (5V max) across the bulk film as a function of pressure via acustom Arduino/Matlab voltmeter. The highest sensitivity was recorded for sampleswith 20% CB by weight, which exhibited a voltage drop of 1.9 V at the maximumloading of 4861 Pa and a maximum rate of 0.380 mV/Pa. The optimum carbon blackloading for maximum sensitivity, 20% by weight, is considerably higher than typicalloadings intended to improve mechanical performance. Accordingly, design ofpressure-sensing composites based on SIBS will likely require careful tradeoff studiesspecific to the requirements of each application. Fortunately, SIBS-based compositesare uniquely suited to this type of application-specific tailoring due to the ability toadjust molecular weight, styrene content, and carbon black loading to achieve a widerange of material performance and functionality.