Drop-on-demand lift-off patterning of compliant electrodes

We present a method for the patterning of compliant electrodes for dielectric elastomer actuators (DEA) using drop-on-demand (DoD) printing and a lift-off process. DoD is a very appealing method for the patterning of electrodes, due to its high resolution, and the design versatility brought by printing from computer files. However, it has very narrow requirements regarding the viscosity, surface tension, and agglomeration size of the solution to be printed, and a new jetting waveform must be developed for each ink. This makes experimenting with new compliant electrode formulations difficult and time-consuming. Our approach consists in printing a water-soluble sacrificial layer on the elastomer, which serves as a mask selectively protecting portions of the membrane. Compliant electrodes can then be applied on the mask by different means (brush, spray coating, stamping etc.), and the mask can subsequently be dissolved to wash away the excess of ink and reveal the pattern, similar to a lift-off process. The inkjet printing process must only be developed and optimized for a single solution (the sacrificial layer), whereas many different electrodes formulations can then rapidly be patterned and tested, without having to meet the requirements of the printer regarding viscosity, surface tension or agglomeration size. We demonstrate the method by patterning an Polyvinylpyrrolidone (PVP) mask. We then use an airbrush to apply a carbon black/silicone mixture over the whole membrane. Finally, we wash away the mask to reveal the compliant electrodes.