The results of recent research on our implantable CMOS biomedical devices are reviewed. Topics include retinal prosthesis devices and deep-brain implantation devices for small animals. Fundamental device structures and characteristics as well as in vivo experiments are presented.

We report a lens-free fluorescence imaging device using a composite filter composed of an interference filter and an absorption filter, each applied to one side of a fiber optic plate (FOP). The transmission of angled excitation light through the interference filter is absorbed by the absorption filter. The auto-fluorescence of the absorption filter is reduced by the reflection from the interference filter of normally incident excitation light. As a result, high-performance rejection of excitation light is achieved in a lens-free device. The FOP provides a flat, hard imaging device surface that does not degrade the spatial resolution. We demonstrate excitation rejection of approximately 10⁸:1 at a wavelength of 450 nm in a fabricated lens-free device. The resolution of fluorescence imaging is approximately 12 µm. Time-lapse imaging of cells containing green fluorescent protein was performed in a 5-µm thin-film chamber. The small dimensions of the device allow observation of cell culturing in a CO₂ incubator. We also demonstrate that the proposed lens-free filter is compatible with super-resolution bright-field imaging techniques. These features open a way to develop a high-performance, dual-mode, lens-free imaging device that is expected to be a powerful tool for many applications, such as imaging of labeled cells and point-of-care assay.

In this work, we present a simple complementary metal-oxide semiconductor (CMOS)-controlled photovoltaic power-transfer platform that is suitable for very small (less than or equal to 1–2 mm) electronic devices such as implantable health-care devices or distributed nodes for the Internet of Things. We designed a 1.25 mm × 1.25 mm CMOS power receiver chip that contains integrated photovoltaic cells. We characterized the CMOS-integrated power receiver and successfully demonstrated blue light-emitting diode (LED) operation powered by infrared light. Then, we integrated the CMOS chip and a few off-chip components into a 1-mm³ implantable optogenetic stimulator, and demonstrated the operation of the device.

We propose and characterize a CMOS LSI-based neural stimulator for retinal prosthesis technology. The stimulator is based upon a multichip architecture in which small-sized CMOS stimulators named ldquounit chipsrdquo are organized on a flexible substrate. We designed a unit chip with an on-chip stimulator and light-sensing circuitry. We verified that all the functions implemented on the unit chip worked correctly and that an organized unit chip can be used as a retinal stimulator with multisite image-based patterned stimulation. We also demonstrated light-controlled retinal stimulation for the first time in an in vivo animal experiment on a rabbit's retina.

In this study, we demonstrate a polarization sensitive pixel for a complementary metal-oxide-semiconductor (CMOS) image sensor based on 65-nm standard CMOS technology. Using such a deep-submicron CMOS technology, it is possible to design fine metal patterns smaller than the wavelengths of visible light by using a metal wire layer. We designed and fabricated a metal wire grid polarizer on a 20 × 20 μm² pixel for image sensor. An extinction ratio of 19.7 dB was observed at a wavelength 750 nm.