Piezoresistive Models These material property groups for piezoresistive materials (including their associated physical properties) can be added to models from the Material window. These property groups require the MEMS Module. Table 9-9: Gas Models Materials Property Group and Property Name/Variable SI Unit Elastoresistance Form Elastoresistive coupling matrix ml Ω·m Piezoresistance Form Piezoresistive coupling matrix Pil A/m2