Piezoresistiv

Piezoresistiv, or the piezoresistive effect, refers to the change in electrical resistance of a material caused by applied mechanical stress. The effect is especially pronounced in semiconductors, where lattice distortion can alter carrier concentration and mobility, but it is also observed in metals, polymers, and composite materials.

In metals, resistance changes mainly through geometric factors during strain, as length increases and cross-sectional area decreases. In semiconductors, changes in band structure and carrier mobility generally produce a larger resistance response, making these materials particularly sensitive for sensing applications. The sensitivity is described by the gauge factor, GF = (ΔR/R) / (ΔL/L). Metals typically exhibit GF around 2, while silicon-based piezoresistors and other semiconductors can achieve substantially higher values.

Materials and devices: Piezoresistive sensing is implemented across a range of materials. Metal foil strain gauges remain common for structural sensing. Silicon-based microelectromechanical systems (MEMS) employ doped silicon piezoresistors for on-chip pressure, acceleration, and force sensing. Flexible polymers and composites incorporating carbon nanotubes, graphene, or other conductive fillers enable stretchable piezoresistive sensors for wearables and soft robotics.

Applications: Piezoresistive devices are used in pressure sensors, tactile sensors, accelerometers, load and force sensors, and structural health monitoring. They offer simple construction, low power consumption, and compatibility with standard microfabrication, while challenges include temperature sensitivity and, in some materials, hysteresis and drift.