Paper-based strain sensing material

We have developed an inexpensive inkjet printing process to fabricate percolation-based resistive strain gauges in a paper substrate. These strain sensors were fabricated by inkjet printing different suspensions containing conductive carbon black (CB). We have measured the resistance of these elements as a function of strain under low frequency cyclic loads to characterize the sensitivity of these sensing materials. Within the range of parameters investigated, our results suggest that a suspension with 3 wt% CB and 0.1 wt% binder has the highest sensitivity with a gauge factor (GF) of up to 70; however, these materials show a limited reproducibility. Devices printed from other suspensions show a lower gauge factor but can have a much higher reproducibility with a coefficient of variation of their GF below 10%. This makes these inexpensive materials ideal for disposable devices that only need to carry out a few measurements such as load and / or impact force measurement with packing material or destructive testing.