Thin and Scalable Hybrid Emission Filter via Plasma Etching for Low-Invasive Fluorescence Detection.

Hybrid emission filters, comprising an interference filter and an absorption filter, exhibit high excitation light rejection performance and can act as lensless fluorescent devices. However, it has been challenging to produce them in large batches over a large area. In this study, we propose and demonstrate a method for transferring a Si substrate, on which the hybrid filter is deposited, onto an image sensor by attaching it to the sensor and removing the substrate via plasma etching. Through this method, we can transfer uniform filters onto fine micrometer-sized needle devices and millimeter-sized multisensor chips. Optical evaluation reveals that the hybrid filter emits light in the 500 to 560 nm range, close to the emission region of green fluorescent protein (GFP). Furthermore, by observing the fluorescence emission from the microbeads, a spatial resolution of 12.11 µm is calculated. In vitro experiments confirm that the fabricated device is able to discriminate GFP emission patterns from brain slices.

Development of Compact Readout Device for Neural Observation System using Fluorescence Imaging and Fast-scan Cyclic Voltammetry.

A readout device for a dual-functional neural observation system is presented. The authors separately developed the reading operation of an implantable CMOS image sensor and a setup for fast-scan cyclic voltammetry and implemented them together in a microcontroller-based device. The developed imaging readout device with a size of [Formula: see text] can reach the highest reading rate of 160 fps with a 120×268 pixel image sensor. The voltammetry function was verified through an experiment using commercial carbon fiber electrodes in phosphate-buffered saline. When the imaging is sequentially operated with 400 V/s-scan rate voltammetry from -0.4 to 1.3 V, the system can operate at up to 60 fps. With this system, calcium imaging and dopamine recording in a freely behaving mouse can be achieved together in a simpler manner. This study aims to be the basis for the development of an implantable multi-functional sensor.

Chronic brain blood-flow imaging device for a behavioral experiment using mice.

A chronic brain blood-flow imaging device was developed for cerebrovascular disease treatment. This device comprises a small complementary metal-oxide semiconductor image sensor and a chronic fiber-optic plate window on a mouse head. A long-term cerebral blood-flow imaging technique was established in a freely moving mouse. Brain surface images were visible for one month using the chronic FOP window. This device obtained brain surface images and blood-flow velocity. The blood-flow changes were measured in behavioral experiments using this device. The chronic brain blood-flow imaging device may contribute to determining the cause of cerebrovascular disease and the development of cerebrovascular disease treatment.