Pencil-on-paper capacitors for hand-drawn RC circuits and capacitive sensing.

Electronic capacitors were constructed via hand-printing on paper using pencil graphite. Graphite traces were used to draw conductive connections and capacitor plates on opposite sides of a sheet of standard notebook paper. The paper served as the dielectric separating the plates. Capacitance of the devices were generally < 1000 pF and scaled with surface area of the plate electrodes. By combining a pencil-drawn capacitor with a resistive element an RC low-pass filter was demonstrated. Further utility of the pencil-on-paper devices was demonstrated through description of a capacitive force transducer (used as a scale) and reversible chemical sensing. The latter was achieved for water vapor when the hygroscopic cellulose matrix of the paper capacitor's dielectric adsorbed water.