Electrospun rubber fibre mats with electrochemically controllable pore sizes

Abstract

Electroactive, elastomeric, microfiber mats that show controllable pore size variation upon electrochemical stimulation are produced from semi-interpenetrating polymer networks (s-IPNs). This type of porous, elastomeric scaffolds that are mechanically dynamic under electrochemical stimuli could find new applications in stretchable electronics, (bio)filtration, soft robotics and stimulation of biological cells.These microfiber mats are prepared in two simple steps. Firstly, a mixture of high molecular weight nitrile butadiene rubber (NBR) and cross-linking agent, poly(ethylene glycol)dimethylacrylate are electrospun with in situ cross-linking. Secondly, a conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) is embedded into the electrospun fibres by oxidative chemical polymerization of EDOT-swollen microfiber mats. This two-step process affords robust, highly flexible and conductive s-IPN microfiber mats. The microfiber mat undergoes a controllable pore size variation upon applying an electrochemical stimulus in the form of a reduction-oxidation cycle to the mats in an electrolyte. The maximum average pore size variation, measured in situ using confocal microscopy, is 25%, achieved in 1 M lithium bistrifluoromethanesulfonimide (LiTFSI) in propylene carbonate (PC) for a potential step between +0.6 V and À0.5 V (vs. Ag wire). These mats also show pore size variation in a biologically compatible solution, phosphate buffered saline. † Electronic supplementary information (ESI) available: Video showing pore size variation in 1 M LiTFSI PC solution, properties and compositions of nonelectrospun films, SEM and EDX of electrospun microfibers and PEDOT embedded fibres respectively, and confocal microscopy and pore size variation data for microfiber mats in PBS solution. See

Flexible and Stretchable PEDOT‐Embedded Hybrid Substrates for Bioengineering and Sensory Applications

“…To create flexible fiber substrates, the electrospun fiber mats (shown in Figure ) were prepared from a solution of NBR and PEGDM, with partial photo‐crosslinking induced during the electrospinning process. Additional crosslinking was achieved by curing at 80 °C in an oven with the use of a thermal crosslinker, as previously reported by us . The random fibers were formed by using a stationary plate collector, while the aligned fibers were fabricated using a custom electrospinning apparatus (Figure A).…”

“…After PEDOT polymerization, we observed the dark blue/black color of the PEDOT‐embedded fiber mat (Figure F) compared with the pristine NBR/PEGDM fiber mats. In addition, the SEM images confirmed the deposition of PEDOT into the NBR/PEGDM fiber network (Figure G) . The PEDOT‐embedded fibers appeared to have a rough surface in comparison to the pristine NBR fibers.…”

“…A second approach consists of incorporating conductive nanoparticles or CPs into/onto the fibers post electrospinning . The latter approach has been employed more commonly, owing to the wider range of materials available to it.…”

“…We overcame PEDOT's drawbacks by incorporating it into flexible and stretchable electrospun rubbery fiber mats forming a semi‐interpenetrating polymer network of two polymers. In this way, the formed mats preserved the elastomeric properties of rubber and the electrical properties of PEDOT …”

“…In this work, a stretchable, biocompatible, robust and conductive electrospun fiber mat is introduced as a substrate or scaffold for flexible and stretchable devices for various biomedical applications. The electrospun fiber mat is specifically composed of a blend of nitrile butadiene rubber (NBR) and poly(ethylene glycol)dimethacrylate (PEGDM) was used for its compatibility of the formed fibers with PEDOT and its effect on ionic conductivity . The resulting electrospun mats are flexible, conductive and contain fibers that are orientated either randomly or aligned.…”