Enhanced actuation performance of silk-polypyrrole composites

Abstract

Recently we have shown that a composite material of silk and the conducting polymer polypyrrole (PPy) has promising characteristics for use as a bending bilayer actuator. In this study, the reaction conditions were varied for the in situ incorporation of polypyrrole into silk films during pyrrole polymerization. While surface morphology and mechanical properties were minimally affected, polymerization conditions were identified where the resistivity, stability of the films during storage and stability during prolonged electrochemical cycling were dramatically improved. When fabricated into bilayer-type electromechanical actuation devices, stress and strain generation, as well as the stability during repeated actuation, was found to be superior for silk-polypyrrole composite films with improved electrical properties.

Performance of silk‐polypyrrole bilayer actuators under biologically relevant conditions

“…Mechanical stress was calculated by dividing the force output during actuation by the cross‐sectional area of the device. A stress of about 3.0 MPa was applied to samples and maintained for 30 min prior to actuation in order to help align the polymer networks and allow samples to relax …”

“…Towards the end of the 20 cycles measured, the linear stress generated for devices tested at room temperature (22 °C) remained within error of the original value at 0.77 MPa, while the values for devices tested at 37 and 43 °C decreased slightly to 0.53 and 0.49 MPa, respectively. However, it is worth noting that the devices continued to generate significant stresses as compared to state‐of‐the‐art silk‐CP actuators at all temperatures over the full 20 cycles shown.…”

“…The linear stress generated by the devices during actuation was measured using an Aurora Dual‐Mode Muscle Lever System . Electrical contact was made to the films by using a wire covered with copper tape and encapsulating the connection with Kapton tape.…”

“…Previously, our group developed strategies for incorporating conductive PPy into silk structures to form a completely integrated interpenetrating network (IPN) of silk and PPy, and demonstrated their use as electromechanical bilayer bending actuators . These silk‐PPy bilayer actuators were capable of generating stresses comparable to human muscle (>0.1 MPa) and were electrochemically stable . While the majority of studies involving CP actuators employ optimized electrolyte systems that use toxic salts or organic solvents, our studies utilized the biomimetic phosphate buffered saline solution (PBS).…”

Polypyrrole-based Conducting and Antibacterial Hybrid Cellulose Membranes: A Study on the Effect of UV Exposure on the Conductivity and Formation of Silver Nanoparticles

“…The surface polymerization of pyrrole monomers has successfully transformed the nonconducting insulating hydrophobic substrates (polyester, silk, wool, and aramid) to conducting flexible substrates that open up avenues for subsequent smart applications. (11)(12)(13) Paper is a form of cellulose regularly used in writing, printing, cleaning, decorating, and packing. Additionally, paper as a filter is readily used as a support for polymers to develop novel functional materials.…”