Study on fabrication of force transducer based on carbon nano-flake balls

The purpose of this study was to fabricate a force sensor. A novel three-dimensional carbon-based material called a carbon nano-flake ball (CNFB) was used because it exhibits a large surface-area and high electrical conductivity. Moreover, CNFB can be easily fabricated using a one-step process via microwave plasma chemical vapor deposition. In the present study, two different methods, chemical and mechanical exfoliation, were used to fabricate the CNFB thin films. CNFEs were successfully synthesized on the silicon-based composite substrate. The substrate was constructed by the Si, SiO₂, and Al₂O₃, where Al₂O₃played the role of the substrate for the force sensor while SiO₂was the interface layer and was removed in the process by hydrogen fluoride (HF) solution to separate Al₂O₃from Silicon. The experiments showed that using sol-gel catalyst coating as pretreatment precursor, results in a larger ball-size but lower deposition density of CNFB on Al₂O₃substrate. By using mechanical exfoliation by polyimide (PI) tape, the CNFB grown on silicon substrate can be easily exfoliated from the substrate. PI/CNFB was successfully exfoliated from the substrate with a silver-grey color at the bottom of the CNFB which is likely to be silicon carbide (SiC) from the energy dispersive spectrometer analysis. The sheet resistance of PI/CNFB was 18.3 ± 1.0 Ω sq.^-1PI/CNFB exhibits a good force sensing performance with good stability after 10 times of loading-unloading cycles and a good sensitivity of 11.6 Ω g^-1.