UC Merced

Conducting polymers offer the ability to create electronic devices that are lightweight with relatively simple processing compared to their inorganic counterparts. They have recently gained attention in the wearable electronics field due their ability to exhibit flexibility and low stiffness while conducting electricity. However, conducting polymers are not intrinsically flexible and must be modified, usually at the expense of electrical performance, or through the use of expensive and toxic additives. Here, we explore the use of architected materials to tune a conductive polymer's mechanical properties without chemical modification. To do so, a reliable and high-throughput 3D printing system for a conducting polymer-based hydrogel was established. The system utilizes a stereolithography apparatus (SLA) to 3D print a hydrogel of almost any 3D shape. The hydrogel acts as a dopant and structural component for a subsequently grown conducting polymer. This means a conducting polymer, which is usually limited to being a thin film or a stochastic foam, can be made into specific and complex geometries, enabling the tailoring of its mechanical properties through architecture, without compositing or chemical modification. When architected into a lattice, the conducting polymers can withstand compressive strain up to 80% without failure, whereas their bulk counterpart reaches just 25% strain before undergoing brittle fracture. The architected conducting polymers also exhibit a strain rate invariant stress-strain curve, suggesting that a potential strain rate invariant electrical resistance behavior may exist, but further investigation is required.