Fabrication of Temperature- and Humidity-Independent Silver Nanoparticle's Carbon Composite-Based Strain Sensor Through Additive Manufacturing Process.

A highly sensitive low-cost strain sensor was fabricated in this research study based on microdispensing direct write (MDDW) technique. MDDW is an additive manufacturing approach that involves direct deposition of functional material to the substrate. The devices were printed directly onto a polymeric substrate by optimizing the fabrication parameters. A composite of silver and carbon was used as active sensor material where both materials in the composite have opposite resistance temperature coefficients. The ratio of materials in the composite was selected so that the effect of temperature on the resistance of overall composite was canceled out. This resulted in achieving temperature compensation or inherent independence of the strain sensor resistance on temperature without requiring any additional sensors and components. The sensor was further encapsulated by electrospray deposition, which is also an additive manufacturing approach, to eliminate the effect of humidity as well. Electrical and morphological characterizations were performed to investigate the output response of the sensors and their physical and structural properties. An analog signal conditioning circuit was developed for seamless interfacing of the sensor with any electronic system. The sensor had an excellent gauge factor of 45 and a strain sensitivity of 45 Ω/μɛ that is higher than most of the conventional strain sensors. The sensor's response showed excellent temperature and humidity compensation reducing the relative effect of temperature on the resistance by ∼99.5% and humidity by ∼99.8%.