A novel needle-free injection system by electrically induced microbubbles has been developed. First of all, we evaluated the depth of injected reagent for evaluating injection performance. Then, the cavitation-induced shock wave has been focused to magnify the injection performance by semi-spherical reflector. We successfully visualized the shock wave by Shlieren method and succeeded in measuring the pressure of focused shock wave and expansion wave by hydrophone.

Conformation and activity control of proteins adsorbed on certain material surfaces enables the development of numerous high-performance applications. Previously, we examined the relationship between the diameter (surface shape) of polyurethane (PU) nanofibers and the conformation/activity of adsorbed protein. Proteins adsorbed on thick nanofibers (diameter: 950 nm) showed decreased activity due to large conformational changes, whereas those adsorbed on thin nanofibers (diameter: 480 nm) retained a close-to-natural shape and thus showed relatively high activity, confirming that the shape of PU nanofiber surface affects the conformation and activity of proteins adsorbed thereon. In this study, in order to prove this hypothesis, the adsorption strength of the adsorbed protein onto the polyurethane nanofiber was evaluated. As a result, it was confirmed that proteins adsorbed on thick nanofibers have higher adsorption strength than thin nanofibers. These results suggested that the thickness of the nanofibers determines the adsorption area between molecule and nanofiber surface, and affects the structure and activity of the adsorbed protein.

Nonspherical monodisperse polydimethylsiloxane (PDMS) microparticles were fabricated by lithography and ultraviolet ozone (UVO) treatment for self-assembly of periodic structures. PDMS solution was poured into photoresist molds on glass substrates, whereupon it was cured at 80°C. After irradiating ultraviolet to the surface of the PDMS, remaining thin PDMS films on the molds were eliminated using ultrasonic waves. Attenuated-total-reflection Fourier-transform infrared spectra indicated that the surface of the UVO treated PDMS was changed to glass SiO₂-like materials, resulting that the remaining thin PDMS films could be ultrasonically removed by fracture. The PDMS microparticles were separated from the substrates using ultrasonic waves, and microparticles of a desired shaped were formed. A suspension was prepared by mixing the PDMS microparticles in deionized water, and a droplet of the suspension was placed on a hydrophobic template substrate. The PDMS microparticles self-assembled on the substrate along the template walls, leading to PDMS microparticles being closely packed. Such PDMS microfabrication would be useful for microdevices.

I developed a MEMS liquid cell for the visualization of bubbles and droplets at the microscale using scanning electron microscope (SEM). The MEMS liquid cell has an electron transparent membrane and a microchannel. The electron transparent membrane was Si₃N₄ of 80 nm in thickness. I tested the wettability of the electron transparent membrane and liquid leakage, and simulated the scattering of an electron beam. The MEMS liquid cell was equipped on the SEM custom-made holder for in-liquid specimens. I observed the bubbles floating in the microchannel and the formation and growth of droplets on the electron transparent membrane at the microscale using SEM.

Glucose detection characteristics were studied for an extended-gate field-effect transistor fabricated by an enzyme immobilization using a long-chain-aminosilane agent. The sensor was able to detect reversibly and repeatedly the glucose concentration in phosphate buffered solution with a considerably low Michaelis constant of 0.045 mg/mL for more than a month. These results indicate that the sensor enables to detect repeatedly such low glucose concentrations as those in sweat and saliva.

This paper addresses measurement with tactile sensor and FEM analysis of multi-layered flexible model for skin diagnosis. In the multi-axial-force MEMS sensor, we evaluated the change of output by contact with the multi-layered flexible object. A test piece similar to human skin consisting of a rigid layer and a flexible layer is prepared. The sensor output depends greatly on the ratio and hardness of the hard layer and the thickness of the flexible layer of the specimen, and the contact surface. Compared with the results of FEM analysis, it is suggested that the difference of the dependence is caused by the constant compressive load applied at the time of shear deformation.