Micromachining of graphene based micro-capacitor using picosecond laser ablation

The present study investigated the characteristics of multilayer graphene micro-capacitor as a capacitive touch sensor. The interdigitated electrode was fabricated using 532 nm picosecond laser. Varying laser fluences were investigated to analyze the effectiveness of using picosecond (PS) laser ablation in patterning graphene based devices. The ablation threshold fluence for machining multilayer graphene on the glass substrate was 0.84 mJ/cm² at a constant scanning speed of 250 mm/s with a repetition rate of 300 kHz. The capacitance in the touched and untouched state as a function of electrode width and length were both investigated of the micro-capacitor. The experiments showed that the sensor capacitance was relatively sensitive to the length of the interdigitated electrode. The sensor capacitance increased approximated linearly as electrode width increased from 200 μm to 600 μm under touched and untouched state. As the electrode width continuously increase W ≥ 600 μm, the sensor capacitance increased sharply under different electrode lengths, especially under touched state. Through the experiments, the purpose of the present work was to demonstrate key parameters and sensing response of the interdigitated graphene based micro-capacitor.