Authors: X. Chen, S. Yang and S. Motojima
Affilation: Gifu University, Japan
Pages: 289 - 292
Keywords: carbon microcoils, carbon nanocoils, tactile sensors
Carbon microcoils/nanocoils (CMC) have an interesting anisotropic morphology of 3D-herical/spiral structure such as a DNA or proteins. The CMC have double-helix or single-helix structure with a coil diameter of 0.05-10 _m and a coil pitch of 0.05-3_m as shown in Figs. 1-4. The CMC have very high elasticity, and the electrical parameters; inductance (L), capacitance (C) and electrical resistivity (R), change by the extension and contraction. The Meissner’s corpuscles, which is the most important tactile receptor of human skin and have helical forms of micron sizes as similar to the CMC. The novel CMC tactile sensor elements (10x10x0.2mm3) were prepared by embedding the CMC by 1-5 wt% addition in elastic polysilicone resin. The changes of LCR parameters of the CMC sensor elements under applying static loads or other stimulations, such as IR-ray, heat, microwaves, sound, etc. were measured using an impedance analyzer. The load or stimulations was applied for about 1-10 sec on the surface of sensor elements and signal change was measured. Fig. 5 shows the changes of L parameter under applying load of 200-1 mgf (20-0.1Pa). It can be seen that L parameter clearly changes under applying a very small load of 1mgf (0.1Pa). The minimum detection ability is below 0.1Pa. This value is 1, 000-10, 000 times higher than that of commercially available tactile sensors. It was found that different kinds of stresses, by pressing a finger, sticking by a needle, picking by tweezers, etc. could be detected by different wave-forms. Fig.6 shows the change of L parameter of the CMC sensor elements under approximating a hand and a heated solder tong, as well as under applying static load of 200mgf. Strong signal changes are observed when a hand or heated solder tong is approximated to the sensor elements. An IR ray is emitted from a hand. Furthermore, it was observed that L and R signal changes was observed when cellular phone or sound was approximated. That is, the CMC tactile sensors can be detected various stresses, temperature, IR, EM waves, etc. with very high detection sensitivity and high discrimination ability. Accordingly, the CMC sensor elements has high potential applications as tactile sensors for endoscopes, catheters, manipulation sheet, etc., or as artificial skin of a humanoid robot, detection sensors of humans buried in debris by earthquake, and various industrial sensors. These properties may be effect by the formation of hybrid LCR oscillation circuit between CMC and dielectric elastic matrix.