| This dissertation presents a microfluidic based tactile sensor mimicking the human slow-adapting mechanoreceptor such as the Merkel's disk. The sensor is composed of a polyimide (PI)/polydimethylsiloxane (PDMS) multilayer structure. The device is composed of a hemispherical reservoir filled with electrolyte solution in the PDMS layer, a microchannel in the PI layer and a pair of sensing electrodes below the microchannel as the force transducer. The tactile signal is detected as the impedance change resulting predominantly from the resistance variance due to the electrodes coverage by the 1M NaCl solution and is measured across the electrode pair. Based on the electrical modeling results, the working frequency is chosen at 1MHz. The sensor response is linear and the working range is shown to be in the range of 0-5 N. From the mechanical modeling results, the sensing range of the devices can be tuned by the diameter of the hemisphere and the mixing ratio of the PDMS. The characterization results also demonstrate the sensing of various levels of forces and its long term signal stability. An distributed 2x2 tactile sensor array with 0.4cm x 0.4cm spatial resolution is also presented. The 2x2 tactile sensor is mounted on the finger tip of a glove and tested. The sensor shows the detection result of the random touch, edge sensation and rolling of a pen. Based on the characterization of the device, the microfluidic based tactile sensor array can be used as a slow adapting sensor array on the fingers of the prosthetic hand. |
