Fabrication of EHD Fiber Pumps for Soft Robots and Wearables

Electrohydrodynamic (EHD) pumps are a promising technology with respect to the development of soft robotics and wearables. Light, compact and silent, EHD pumps provide a useful pressure source for the fluidic actuators which are fundamental to much of soft robotics. Indeed, as first demonstrated in our group, EHD pumps can themselves be created from soft materials.<br/><br/>Despite this, however, the planar configuration of interdigitated electrodes which almost exclusively characterizes EHD pumps does not necessarily lend itself to straightforward integration within wearables: flexibility is essentially constrained to one direction, and achieving stretchable electrodes requires the use of specialized materials.<br/><br/>In this work, we detail how soft EHD pumps can be produced in a fiber format. Through a filament winding method, thin copper wire and polyurethane thread are twisted together to create mm-wide hollow tubes with continuous helical electrodes embedded within the walls. By applying an electric field strength of order 10 kV/mm between these electrodes, centimeter lengths of pump can generate more than 8 kPa of pressure and 15 ml/min of flowrate in a fluorinated dielectric liquid. The fiber form factor affords flexibility in all directions, simplifying integration into wearables, while the use of helical structures means stretchable electrodes can be achieved using conventional metallic wire.