For our paper-based MEMS sensors, we developed a
monolithic approach that integrated the whole Wheatstone
bridge circuit with the paper-based sensor. This approach
was inspired by a previous paper [11], which used paper as a
flexible PCB for construction of circuits. As shown in Figure
3B, we laid out connections of the entire Wheatstone bridge
circuit (including the carbon resistor Rs) by screen-printing
silver ink on the base of the paper-based sensor, then gluing
three surface-mount resistors (R1, R2, R3) at appropriate
locations, and finally ‘solding’ them into the circuit using
silver ink. R3 is an adjustable resistor that is used to initially
balance the Wheatstone bridge.