Both the electrical conductivity and the piezoresistive or elastoresistive coupling matrix are strong functions of the material dopant density. The material models include appropriate functions, although the piezoresistive and elastoresistive matrices scale only with the conductivity, which is appropriate only at lower dopant densities (below approximately 1016 cm−3). The low doping level piezoresistance and elastoresistance values are based on those given in Ref. 1. The conductivity is computed from an empirical functional fit to experimental data given in equation 8 of Ref. 2. Data on the piezoresistance properties of Silicon at higher doping levels is available in Ref. 3 and Ref. 4. Because this data does not include all components of the coupling matrix, it is not included in the material models.