Design and Fabrication of a Metal Resistance Strain Sensor With Enhanced Sensitivity

This letter reports a novel design of a resistance strain sensor and its method of fabrication. The sensor is made of printed silver (Ag), but its sensitivity, which is measured by the gauge factor (GF), surpasses most commercial metal foil strain gauges (COTS). These COTS have a low GF (∼2) because they exhibit a weak piezoresistive effect. As a result, their sensitivity is dominated by the geometric effect. In this design, the GF is not limited by the weak piezoresistive effect in Ag. Its enhanced sensitivity (GF∼55) originates from the junctions that are created when a conductive cross-pattern is laser sintered on a printed Ag pad. The cross-pattern consists of a low-resistivity vertical trace and a high-resistivity horizontal trace. The difference in resistivity is achieved by changing the laser sintering power. The junction that joins the high and the low resistivity traces is a boundary with interfacial resistance. This interfacial resistance exhibits high sensitivity to strain leading to a different design and fabrication of a resistance strain sensor.