Implantable Image Sensor Research Articles

Image sensor with hybrid emission filter for in vivo fluorescent imaging

AbstractIn this paper, we report a method of fabricating an implantable image sensor equipped a bandpass hybrid filter for highly sensitive fluorescence observation. A hybrid filter that combines an interference filter and an absorption filter enables a high excitation light removal performance in an implantable image sensor that does not use a lens. In this study, a thin hybrid filter was successfully mounted on the image sensor using the transfer method by using a laser lift‐off technique. The transferred filter has no crack. It was demonstrated that the prototype device exhibited high excitation light removal performance and was able to acquire a fluorescent image with high contrast.

Wireless image-data transmission from an implanted image sensor through a living mouse brain by intra body communication

Intra body communication technology allows the fabrication of compact implantable biomedical sensors compared with RF wireless technology. In this paper, we report the fabrication of an implantable image sensor of 625 µm width and 830 µm length and the demonstration of wireless image-data transmission through a brain tissue of a living mouse. The sensor was designed to transmit output signals of pixel values by pulse width modulation (PWM). The PWM signals from the sensor transmitted through a brain tissue were detected by a receiver electrode. Wireless data transmission of a two-dimensional image was successfully demonstrated in a living mouse brain. The technique reported here is expected to provide useful methods of data transmission using micro sized implantable biomedical sensors.

Implantable self-reset CMOS image sensor and its application to hemodynamic response detection in living mouse brain

A self-reset pixel of 15 × 15 µm2 with high signal-to-noise ratio (effective peak SNR ≃64 dB) for an implantable image sensor has been developed for intrinsic signal detection arising from hemodynamic responses in a living mouse brain. For detecting local conversion between oxyhemoglobin (HbO) and deoxyhemoglobin (HbR) in brain tissues, an implantable imaging device was fabricated with our newly designed self-reset image sensor and orange light-emitting diodes (LEDs; λ = 605 nm). We demonstrated imaging of hemodynamic responses in the sensory cortical area accompanied by forelimb stimulation of a living mouse. The implantable imaging device for intrinsic signal detection is expected to be a powerful tool to measure brain activities in living animals used in behavioral analysis.

Digital signal transmission from fully implantable CMOS image sensor in simulated body environment

A method for wireless data transmission from an implantable image sensor through the biological tissue as a conductive medium is reported. A battery-powered implantable image sensor unit is dipped in phosphate-buffered saline (PBS) as the simulant body solution and received the data signal through the PBS. Its equivalent circuit model for simulation is also proposed. The transmitted signal waveforms are in good agreement with the simulation result. Image recovery from the signal obtained from the implantable image sensor received outside the PBS is also demonstrated.

Functional brain fluorescence plurimetry in rat by implantable concatenated CMOS imaging system

Measurement of brain activity in multiple areas simultaneously by minimally invasive methods contributes to the study of neuroscience and development of brain machine interfaces. However, this requires compact wearable instruments that do not inhibit natural movements. Application of optical potentiometry with voltage-sensitive fluorescent dye using an implantable image sensor is also useful. However, the increasing number of leads required for the multiple wired sensors to measure larger domains inhibits natural behavior. For imaging broad areas by numerous sensors without excessive wiring, a web-like sensor that can wrap the brain was developed. Kaleidoscopic potentiometry is possible using the imaging system with concatenated sensors by changing the alignment of the sensors. This paper describes organization of the system, evaluation of the system by a fluorescence imaging, and finally, functional brain fluorescence plurimetry by the sensor. The recorded data in rat somatosensory cortex using the developed multiple-area imaging system compared well with electrophysiology results.

Implantable Image Sensor with Light Guide Array Plate for Bioimaging

We propose and demonstrate the fabrication of a light guide array (LGA) structure to improve the spatial resolution of an implantable image sensor. An LGA structure is composed of an array of holes with a high aspect ratio. By restricting the incident angle into image sensor pixels, unwanted incident light is eliminated and degradation of the spatial resolution owing to the gap from the image sensor is reduced. An LGA plate is fabricated by etching holes on a silicon wafer. The LGA plate is embedded on an image sensor and the improvement of spatial resolution is verified. As an example, images of fluorescent beads were obtained using the image sensor with the LGA plate. The imaging contrast and resolution were successfully enhanced.