Investigating Branched Polyethylene Sensors for Applications in Prosthetics

There is a need for new conductive, scalable sensors with piezoresistive and thermoresistive properties for applications in bioengineering. For example, the demand for real-time sensory feedback in upper-limb prosthetics requires sensors that are low-cost, scalable, and sensitive to temperature, pressure, and movement. It is possible to manufacture low-cost conductive sensors by directly mixing a low-cost filler such as graphite into fillers such as polyorganosiloxane, although they can have poor electrical and mechanical homogeneity. In this paper, an alternative approach is outlined to form these sensors: ethylene was polymerized using a nickel catalyst to form a polymer with up to 93 branches per 1000 carbon atoms. This branched polyethylene was fibrous and had a greater volume than high-density polyethylene. After hot pressing with a graphite filler to form a conductive, flexible sensor, the polyethylene samples had electrical resistivity down to approximate to 0.067 omega m, a thermal coefficient of resistance approximate to-7.5 omega circle C-1 at 27 circle C, and a electrical resistance sensitive to forces down to 0.1 N. The process is scalable, and provides a route to homogeneous, low-cost sensors for future prosthetics applications.