Inkjet-printed strain sensors for monitoring cylindrical pressure vessels

The demand for flexible, low-cost, and lightweight sensors is increasing, particularly for structural health monitoring in harsh environments exposed to temperature fluctuations and mechanical strain. Inkjet printing, an additive manufacturing technique for electronics, offers low-cost fabrication with high spatial resolution. In this work, we present strain sensors fabricated by inkjet-printing silver onto flexible Kapton substrates. The sensing grid is protected from the environment by a polymeric encapsulant. The sensors exhibit a linear increase in resistance with increasing strain, with gauge factor values ranging from 1.40 to 1.80 recorded over a temperature range of −40 to 100 °C. Furthermore, we demonstrate the applicability of these sensors for monitoring the mechanical deformation of a propellant tank with an aluminum liner. The strain sensor was printed directly onto the Kapton, which was pre-glued on a curved surface (tank). To compensate for temperature effects, two strain gauges, i.e., one aligned in the hoop direction and the other in the axial direction, were connected in a half-Wheatstone bridge configuration. A linear increase in output voltage with rising internal pressure up to 50 bar was observed, confirming the potential of inkjet-printed sensors for direct integration into structural health monitoring systems.