Stretchable Bioelectrodes
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1271-JJ01-04
Stretchable Bioelectrodes
Pinghung Wei and Babak Ziaie Birck Nanotechnology Center, Purdue University, W. Lafayette, IN, 47907, USA. ABSTRACT
In this paper, we present a stretchable electrode array for studying cell behavior subjected to mechanical strain. The electrode array consists of four gold nail-head pins (250μm tip diameter and 1.75mm spacing) or tungsten microwires (25.4μm in diameter) inserted into a polydimethylsiloxane Fusible indium alloy (liquid at room temperature) filled (PDMS) platform (25.4x25.4mm2). microchannels were used to connect the electrodes to the outside, thus providing the required stretchability. The electrodes were able to withstand strains of up to 40%. Repeated strain tests of several hundred cycles did not reveal any failure, illustrating the robustness of the platform. Mice cardiomyocytes and chick neurons were successfully cultured onto the platform.
INTRODUCTION
Strechable electrodes as cell culture platforms have recently garnered particular attention for their utility in studying cellular behavior central to several important pathologies such as traumatic brain injury, cardiomyopathy, and vascular disorders. A central theme common to these diseases is the subjection of tissue to strain. The ability to record and stimulate nerve and muscle cell populations while subjecting them to mechanical strain can provide insights into mechanism of the aforementioned diseases. In addition, stretchable electrodes can be used to study stem cell differentiation since it is widely believed that mechanical cues are important in this process. Most reported stretchable electrodes are based on the evaporation of a thin gold layer on a PDMS substrate [1-5]. While many of these electrodes can be stretched to tens of percent, they can suffer from gold line disconnection or delamination due to poor adhesion between gold and PDMS. In this work, we present a stretchable electrode array using room temperature liquid-alloy filled microchannels as interconnects and miniature gold nail-head pins or tungsten microwires as the electrodes. Liquid alloy allows for repeated strains beyond what is typically achievable by thin metal films on elastomeric substrates while providing robustness for applications that require numerous (hundreds) cycles of strain.
STRETCHABLE PLATFORM
Figure 1 shows a schematic of the cell stretchable electrode array which consists of two PDMS layers. The top layer incorporates sub-surface liquid-alloy-filled microchannels and provides a biocompatible exterior surface for cell culture. The bottom layer is bonded to the top layer, sealing the microchannels. Gold coated nail-head pins acting as electrodes are placed in the channels with their
sharp head punched through the top PDMS layer and their flange-shaped nail-head bottom flush against the PDMS sealing the junction against the leakage of alloy into the culture medium.
Figure 1. Schematic of the stretchable electrode array.
FABRICATION PROCE
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