A Percolation Model for Piezoresistivity in Conductor–Polymer Composites

Advanced Theory and Simulations 2019 Volume 2, Issue 2, Article 1800125

Insulating polymer composites with conductive filler particles are attractive for sensor applications due to their large piezoresistive response. Composite samples composed of a polymer matrix filled with particles of doped semiconductor that gives a piezoresistive response that is 105 times larger than that of bulk semiconductor sensors are prepared here. The piezoresistance of such composite materials is typically described by using a tunneling mechanism. However, it is found that a percolation description not only fits prior data better but provides a much simpler physical mechanism for the more flexible and soft polymer composite prepared and tested in this study. A simple model for the resistance as a function of applied pressure is derived using percolation theory with a conductivity exponent, s. The model is shown to fit experimental piezoresistive trends with the resistance measured both perpendicular and parallel to the pressure direction.