Pencil drawn interdigitated capacitive sensors on wood substrate

Abstract

This research presents the fabrication and characterization of an interdigitated capacitive (IDC) sensor on a wooden substrate using pencil traces. The resistance of the pencil traces decreased from 100 kΩ to 5 kΩ as the pencil grade shifted from HB to 8B. Concurrently, capacitance measurements revealed an increase from approximately 5 pF for a 5-finger IDC made with HB pencil to around 32 pF for an 8B pencil counterpart. Increasing the number of pencil traces from 10 to 50 resulted in a significant decrease in resistance and a proportional increase in capacitance. Application of the IDC sensor demonstrated notable changes in capacitance upon proximity and touch, with a significant decrease upon removal. The interdigitated capacitance sensor exhibits good proximity effects and contact sensitivity in touch, with capacitance increasing exponentially from 0.3 pF (7 cm) to 1.2 pF (direct contact), highlighting its ability to detect objects with high precision. Additionally, environmental factors such as temperature and humidity influence capacitance values. These findings underscore the potential of pencil-drawn IDC sensors for responsive and adaptable applications in various fields.