Selective Laser Based Postprocessing to Convert Flexible Printed Circuits into Stretchable Circuits and Their Use in Biomedical Applications

Flexible printer circuit boards (Flex-PCBs) have become ubiquitous in commercial electronics and are pervasive across multiple industries. These components can bend and flex, allowing them to be used in a wide variety of interconnects and durable circuits, but they cannot accomodate significant in plane strain. More recently, a wide variety of applications have been demonstrated based on the use of fully stretchable sensors, that can undergo this type of deformation. In particular, because tissues are intrinscially soft and stretchable, and anatomies tend to be complex and unique, there are a wide variety of biomedical application where the ability of sensor to stretch and deform themselves to make intimate contact with tissue presents unique benefits.<br/>A wide variety of wearable and soft robotics systems have been developed demonstrating the importance of these novel classes of devices. These are based on a wide variety of fabrication methods ranging from sophisticated approaches to use advanced fabrication of traditional brittle electronic materials, rendering them stretchable, to the use of novel materials that are intrinsically stretchable. We have demonstrated a low cost method to employ these design strategies, coupled with a self-aligned laser based postprocessing method to convert traditional Flex-PCBs into stretchable sensing arrays. We have demonstrated these approaches for both single and multilayer Flex-PCBs.<br/>Here, we will describe this methodology. Fursthermore, we will describe thermal simulations to understand the underlying mechanisms for this process. We use these simulations to understand the basic design trade-offs associated with this method, such as limits to resolution, number of layers, and other process parameters.<br/>Seperately, we describe the utility of these approaches by describing several practical demonstrations of biomedical devices that utilize these types of stetchable electronics, based on laser-based postprocessed Flex-PCBs. Here we describe the ability of these arrays to be easily integrated with stetchable biomedical grade polyurethanes for applications in cardiac mapping and patient intubation.