Electrical responses of conductive nylon for application in low cost exoskeletons for stroke rehabilitation

Abstract

Despite the rising popularity of robotic exoskeletons, high cost and bulkiness are two limitations that hinder their popularity and everyday use. Our overarching goal is to develop an electrically powered low-cost lightweight exoskeleton for stroke rehabilitation by expanding upon previous research showing that nylon can be utilized as an artificial muscle. Nylon fishing line and silver coated nylon were used as materials for coil production. Lines were twisted together into coils, keeping consistent contact throughout testing. Voltages were generated, while keeping tension on a coil, using a single channel function generator with frequencies of 1Hz and 2Hz, and voltages ranging from 500mV to 3V in increments of 500mV. Unexpectedly, when voltage was applied to coils no response was seen, except for an observed contracting force at one volt in each frequency. Conductive artificial muscle coils displayed contracting forces with at least one voltage level. Given that coils only responded to one volt and coil resistance did not vary significantly, we infer that the response was produced from a combination of the coils voltage and current level. Current work is focusing on developing more coils that can be tested for a wider range of voltage/current levels. Future work will focus on testing additional conductive nylon varying in resistance. This study represents an important step towards designing artificial muscles that are electrically controlled. These muscles have shown the potential to be electrically powered and controlled, giving promise to electrically powered soft exoskeletons in future work which could replace bulky motor and actuator driven robotics altogether.