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This paper reports on a CMOS fully integrated optoelectronic sensing system composed of a Si photodiode and a transimpedance amplifier acting as the electronic analog front-end for the conditioning of the photocurrent generated by the photodiode. The proposed device has been specifically designed and fabricated for wearable/portable/implantable biomedical applications. The massive employment of sensor systems in different industrial and medical fields requires the development of small sensing devices that, together with suitable electronic analog front ends, must be designed to be integrated into proper standard CMOS technologies. Concerning biomedical applications, these devices must be as small as possible, making them non-invasive, comfortable tools for patients and operating with a reduced supply voltage and power consumption. In this sense, optoelectronic solutions composed of a semiconductor light source and a photodiode fulfill these requirements while also ensuring high compatibility with biological tissues. The reported optoelectronic sensing system is implemented and fabricated in TSMC 180 nm integrated CMOS technology and combines a Si photodiode based on a PNP junction with a Si area of 0.01 mm2 and a transimpedance amplifier designed at a transistor level requiring a Si area of 0.002 mm2 capable to manage up to nanoampere input currents generated by the photodiode. The transimpedance amplifier is powered at a 1.8 V single supply showing a maximum power consumption of about 54 μW, providing a high transimpedance gain that is tunable up to 123 dBΩ with an associated bandwidth of about 500 kHz. The paper reports on both the working principle of the developed ASIC and the experimental measurements for its full electrical and optoelectronic characterizations. Moreover, as case-examples of biomedical applications, the proposed integrated sensing system has also been validated through the optical detection of emulated standard electrocardiography and photoplethysmography signal patterns. [ABSTRACT FROM AUTHOR]

An infant’s brain effortlessly acquaints to a motion. Fetuses in the third trimester of pregnancy can also exhibit similar capacity, but further investigations on this matter are needed. Literature studies have assessed fetal response to visual stimulus experiments, but the known setups are reinforced with fixed illumination points and cannot be used to render generic motion visually. This work presents a system to overcome this limitation, i.e., provide dynamic motion as a visual stimulus for fetuses in the third trimester of pregnancy when they can process visual stimulus, and thus biological motion can be used for assessing fetal reactions. Our Transcutaneous Fetal Visual Stimulator (TCFVS) uses two high-resolution LED arrays (16 $\times $ 20), a reconfigurable SoC (Xilinx FPGA and ARM core), and intuitive software to provide flexible control and ease of operation analyzing fetal reactions in response to visual stimulation. The paper details the TCFVS hardware and software architecture and presents benchmarks on the software toolchain to import generic patterns or motion capture in the visual stimulation domain. Our ad-hoc pixel remapping technique, an important component to precisely visualize stimulations in our hardware, is necessary and results in higher performance with respect to conventional downscaling techniques. To provide the first validation of our device in view of a systematic study, we verified real fetus movements when stimulated with TCFVS.