Optimization of Silk Films for Use in Composite Conducting Polymer Actuator Devices

jordan donohue, Western Washington University
Rebecca Szabo, Western Washington University

Abstract

The biocompatibility of conducting polymers (CPs) makes them promising for a variety of biomedical applications such as devices capable of biomimetic movements (artificial muscles). CPs are capable of expansion or contraction when an electric potential is applied in the presence of electrolyte, allowing them to function as actuators in biological fluids. Unfortunately, CPs are brittle and difficult to process. We have developed a method to create an interpenetrating network of silk and CP that combines the excellent mechanical strength of silk and the conductive properties of the polymer, while maintaining biocompatibility. These composite films have been shown to function as actuators in biologically relevant electrolytes. Here, we explore three methods to further optimize and expand the versatility of these composites: 1) Nanopatterning. Methods to produce silk substrates with nanoscale grooves are being developed. These parallel grooves are anticipated to enhance bilayer actuation and dictate direction of movement. 2) Decreasing beta-sheet content. The beta-sheet crystalline regions of regenerated silk films give them mechanical strength, but in excess cause brittleness. Various annealing methods are evaluated to control beta-sheet content and improve flexibility. 3) Silk-chitin films. The addition of chitin nanofibers to silk films is evaluated to improve mechanical properties, conductivity, and actuation.

 
May 14th, 10:00 AM May 14th, 2:00 PM

Optimization of Silk Films for Use in Composite Conducting Polymer Actuator Devices

Chemistry

The biocompatibility of conducting polymers (CPs) makes them promising for a variety of biomedical applications such as devices capable of biomimetic movements (artificial muscles). CPs are capable of expansion or contraction when an electric potential is applied in the presence of electrolyte, allowing them to function as actuators in biological fluids. Unfortunately, CPs are brittle and difficult to process. We have developed a method to create an interpenetrating network of silk and CP that combines the excellent mechanical strength of silk and the conductive properties of the polymer, while maintaining biocompatibility. These composite films have been shown to function as actuators in biologically relevant electrolytes. Here, we explore three methods to further optimize and expand the versatility of these composites: 1) Nanopatterning. Methods to produce silk substrates with nanoscale grooves are being developed. These parallel grooves are anticipated to enhance bilayer actuation and dictate direction of movement. 2) Decreasing beta-sheet content. The beta-sheet crystalline regions of regenerated silk films give them mechanical strength, but in excess cause brittleness. Various annealing methods are evaluated to control beta-sheet content and improve flexibility. 3) Silk-chitin films. The addition of chitin nanofibers to silk films is evaluated to improve mechanical properties, conductivity, and actuation.