Low-cost and versatile integration of microwire electrodes and optical waveguides into silicone elastomeric devices using modified xurographic methods

Microelectrodes are used in microfluidic devices for a variety of purposes such as heating, applying electric fields, and electrochemical sensing. However, they are still manufactured by expensive deposition techniques such as sputtering or evaporation and patterned using photolithography methods. More recently, alternate methods including nanoparticle sintering and use of liquid metal flowing through microchannels have been used to fabricate microelectrodes. These methods are limited in the material choices or require post processing to be integrated into microchannels. Here we developed a low-cost and versatile method to integrate high-quality metal microwires into polydimethylsiloxane (PDMS) using xurography. The microwire integration process includes cutting slit pattern on PDMS substrate and subsequent writing metal microwires into the slit pattern using a specialized tip. Then the microwire-integrated PDMS was sealed/bonded using uncured PDMS prepolymer. This method enables integration of metal microwires of diameter as small as 15 μm into PDMS devices. Integration of multiple microwires with minimum spacing of 150 μm has also been demonstrated. The versatility of this method is demonstrated by the fabrication of metal microwire suspended in the middle of the microchannel, which is difficult to achieve using conventional electrode fabrication methods. This low-cost method avoids expensive clean room fabrication yet producing high-quality electrodes and can be used in a variety of microfluidic and MEMS applications.