A piezoresistive dielectric elastomer switch consisting of inkjet-printed carbon black

Abstract

The piezoresistive effect is a key physical property utilized in soft and stretchable electronics, functioning as intrinsic electromechanical sensors. However, most conventional piezoresistive sensors can only passively measure and quantify external stimuli. To address these limitations, this work integrates an inkjet-printed piezoresistive pattern and a dielectric elastomer actuator (DEA) into a single monolithic dielectric elastomer film, creating a dielectric elastomer switch (DES). This DES can realize dramatic resistance changes along with DEA actuation, leveraging DEA-driven piezoresistivity for active and effective circuit control and signal processing. Theoretically, the DES operates by exhibiting resistance change through the periodic compression induced by DEA actuation. Experimentally, the piezoresistive pattern and the DEA electrodes were fabricated on an acrylic dielectric elastomer (VHB) using inkjet-printed piezoresistive carbon black (CB) and manually brushed conductive grease, respectively. The optimized DES demonstrated approximately 3.77 (±0.11) orders of magnitude in resistance change at a DEA frequency of 0.1 Hz. Compared to previously reported methods (smearing and stamping), inkjet-printed CB patterns showed significant improvements. These included negligible Joule heating impact, precise digital fabrication control, larger resistance change (up to 3.77 orders of magnitude), faster response speeds to DEA actuation (∼0.25 s for 3 orders of magnitude in resistance change), and greater durability (operating at 0.5 Hz for 112 min). Scanning electron microscopy (SEM) characterization revealed that these improvements were attributed to a more uniform distribution of conductive “CB islands” and appropriate non-conductive gap size among them. For demonstrating the applications of DES, it was employed for LED control, DEA-based soft gripper control, and as a multiplexer for signal processing.