Biochar: A “green” carbon source for pressure sensors

Biochar obtained from pyrolysis of plant biomass is an alternative “green” carbon source for manufacturing pressure sensors based on polymer foams. In this study, biochar from pyrolysis of rice husk in the extraction of liquid fuel was explored as fillers. Biochar/PDMS foams were fabricated using sugar templating method. Mechanical and pressure sensing properties were investigated by static and cyclic loading of a sensing device in which a Biochar/PDMS foam is sandwiched between copper electrodes. Biochar/PDMS foams fabricated display negative pressure coefficient of resistance (NPCR) in which electrical resistance decreases applied with pressure. The observed NPCR behavior is attributed to formation of additional conducting paths formed between carbon particles protruding from pore walls during compression. Electrical resistance decreases in-sync with applied pressure over 1 mm/min to 150 mm/min compression rate. Electrical response of Biochar/PDMS foam is comparable to recent reports using nanostructured carbon as fillers.