A new, low-cost, PDMS metallization process for highly conductive flexible and stretchable electronics

This thesis describes a novel microfabrication process to produce thick-film copper microstructures that are embedded in polydimethylsiloxane (PDMS). This process has reduced fabrication complexity and cost compared to existing techniques, and enables rapid prototyping of designs using minimal microfabrication equipment. This technology differs from others in its use of a conductive copper paint seed layer and a unique infrared-assisted transfer process. The resulting microstructures are embedded flush with the PDMS surface, rather than on top, and adhere to PDMS without the need of surface modifications. The 70-micrometers-thick copper layer has a surface roughness of approximately 5 micrometers, a low film resistivity of 2.5-3 micro-Ohm-cm, and can be patterned with feature sizes of 100 micrometers. The low-cost, thick metal films demonstrate a comparative advantage in high-current, low-power applications, with feature sizes and metal layer properties that are otherwise comparable to similar processes. Several applications are fabricated, including stretchable interconnects integrated with fabrics for wearable devices and a multi-layer electromagnetic microactuator with a soft magnetic nanocomposite polymer core for large magnetic field generation. The interconnects can accommodate strains of 57 percent before conductive failure, which is similar to existing technology, and demonstrate a significantly lower resistance of less than 0.5 Ohm per device. The actuator produces an average magnetic field of 2.5 milli-Tesla per volt applied within a cylindrical volume of 34 cubic millimeters. Simulations indicate that fields of up to 1 Tesla are possible for 200 micro-second input pulses, and that significantly larger fields are achievable through simple design modifications. These results are comparable to existing devices, while our device has the advantage of being fully flexible, low-cost, and is easily integrated with various substrates and polymer microfabrication processes.