We have developed a fiber-optic Fabry–Perot interferometric pressure sensor of 125 µm in diameter and a detection system for medical use. A Fabry–Perot cavity is formed at an optical fiber end. A deformation of the diaphragm of the Fabry–Perot cavity induced by pressure varies the cavity length. White light interferometry is used to avoid error and noise caused by bending of the optical fiber and fluctuation of the light source. The reflection light of the sensor cavity is detected by a commercial high-speed spectrometer. A pressure change has been detected by using the developed sensor system. Animal experiments using a goat have been carried out and dynamic pressure changes in the internal pressure of heart and aorta have been successfully monitored.

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Three-dimensional (3D) photoresist patterns of which shape is precisely controlled are fabricated using a gray-scale photolithography. We utilize a maskless exposure system to achieve the precise gray-scale photolithography at low cost. Multilayered exposure patterns digitally generated by the maskless exposure system are superposed on a photoresist-coated substrate layer by layer. Changing the exposure patterns and the exposure parameters such as the exposure time and the scanning speed of the stage of each exposure make the precise control of the profile of UV dose possible. The exposure process does not require any hard masks such as expensive gray-scaled hard masks; therefore, a fabrication of variable 3D patterns at low cost can be achieved, which is an advantage for developing microelectromechanical systems devices. A spherical and an aspherical microlens and its arrayed patterns of 100μm in diameter and 6μm in height are fabricated by a superposition of sixteen-layered exposure patterns. The profile of the fabricated microlens pattern deviates from that of the designed microlens pattern by less than 0.2μm.

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