Retinal implants aim to partially restore vision to patients suffering from blindness caused by age-related macular degeneration (AMD) or retinitis pigmentosa (RP). Up until now, most prostheses were powered using an inductive link coupled with cables penetrating through the eyeball. Although they efficiently power the implant, they limit long-term reliability and cause postoperative complications. A fully wireless near-infrared power and data link entering the eye through the pupil alleviates these issues but limits the available power and causes energy supply interruptions during blinking. This article presents a retinal implant ASIC architecture optimized for optical operation despite these constraints. It contains 288 individually controlled electrode drivers, each connected to electrode pads with a pitch of 150 μm. A digital controller with a stateless communication scheme allows flexible stimulation sequences and is capable of restoring stimulation within 3 ms after an eye blink. The prototype was fabricated using a CMOS 65-nm low-power technology and occupies an area of 2.8 × 3.1 mm ² with a static power consumption of 3.1 mW.

The design and benchtop operation of a wireless miniature epiretinal stimulator implant is reported. The implant is optically powered and controlled using safe illumination at near‐infrared wavelengths. An application‐specific integrated circuit (ASIC) hosting a digital control unit is used to control the implant's electrodes. The ASIC is powered using an advanced photovoltaic (PV) cell and programmed using a single photodiode. Diamond packaging technology is utilized to achieve high‐density integration of the implant optoelectronic circuitry, as well as individual connections between a stimulator chip and 256 electrodes, within a 4.6 mm × 3.7 mm × 0.9 mm implant package. An ultrahigh efficiency PV cell with a monochromatic power conversion efficiency of 55% is used to power the implant. On‐board photodetection circuity with a bandwidth of 3.7 MHz is used for forward data telemetry of stimulation parameters. In comparison to implants which utilize inductively coupled coils, laser power delivery enables a high degree of miniaturization and lower surgical complexity. The device presented combines the benefits of implant miniaturization and a flexible stimulation strategy provided by a dedicated stimulator chip. This development provides a route to fully wireless miniaturized minimally invasive implants with sophisticated functionalities.

A better timing resolution for positron emission tomography (PET) detectors adds time-of-flight information to increase the image contrast. The timing resolution can be improved by timestamping multiple photons from a scintillation event and combining the information using the mean or the Gauss-Markov estimator. To circumvent the performance degradation incurred by these estimators at higher dark count rates (DCRs), two dark count resilient algorithms were studied independently in the literature: the filtered Gauss-Markov and the artificial neural networks. This paper presents parametric simulations that compare them under different DCR conditions. We studied two different types of scintillator-based digital silicon photomultipliers: a typical 1×1×10 LYSO:Ce crystal paired with a 180 ps single photon timing resolution (SPTR) photodetector and a fast 1×1×3 LYSO:Ce:Ca crystal paired with a 35 ps SPTR photodetector. For a single photon avalanche diode with DCR over 1 , simulations show a significant coincidence timing resolution (CTR) gain when using the filtered Gauss-Markov estimator, improving the CTR of the typical detector by 10 % and the fast detector by 33 % over the unfiltered Gauss-Markov estimator. In all evaluated cases, the filtered Gauss-Markov estimator yields the lowest CTR.

Clinical trials previously demonstrated the notable capacity to elicit visual percepts in blind patients affected with retinal diseases by electrically stimulating the remaining neurons on the retina. However, these implants restored very limited visual acuity and required transcutaneous cables traversing the eyeball, leading to reduced reliability and complex surgery with high postoperative infection risks. To overcome the limitations imposed by cables, a retinal implant architecture in which near-infrared illumination carries both power and data through the pupil to a digital stimulation controller is presented. A high efficiency multi-junction photovoltaic cell transduces the optical power to a CMOS stimulator capable of delivering flexible interleaved sequential stimulation through a diamond microelectrode array. To demonstrate the capacity to elicit a neural response with this approach while complying with the optical irradiance limit at the pupil, fluorescence imaging with a calcium indicator is used on a degenerate rat retina. The power delivered by the laser at the permissible irradiance of 4 mW/mm2 at 850 nm is shown to be sufficient to both power the stimulator ASIC and elicit a response in retinal ganglion cells (RGCs), with the ability to generate of up to 35 000 pulses per second at the average stimulation threshold. This confirms the feasibility of generating a response in RGCs with an infrared-powered digital architecture capable of delivering complex sequential stimulation patterns at high repetition rates, albeit with some limitations.

This paper presents a fully-CMOS, tunable impulse radio ultra-wideband (IR-UWB) transmitter for high-density implantable neural recording systems. Fabricated in 28 nm CMOS technology, the transmitter features an ultra-compact edge-combining architecture based on a digitally tunable impulse response filter (IRF) occupying only $0.0027~ {\mathrm {\text {m}\text {m} ^{2}}}$ . The measured output exhibits a central frequency of $4.5~ {\mathrm {\text {G}\text {Hz} }}$ with a 10-dB bandwidth of $3.6~ {\mathrm {\text {G}\text {Hz} }}$ , providing robust spectral performance. It achieves $1~ {\mathrm {\text {G}\text {Hz} }}$ frequency tunability by adjusting pulse widths from $650~ {\mathrm {\text {p}\text {s} }}$ to $800~ {\mathrm {\text {p}\text {s} }}$ , ensuring compliance with FCC spectral masks. A current-starved ring VCO (CSRVCO), with a compact $150~ {\mathrm {\mu \text {m} ^{2}}}$ layout, serves as the clock source, offering wide frequency tuning, low power consumption, and enhanced output power. The transmitter employs On-Off Keying (OOK) modulation and delivers a peak output amplitude of $660~ {\mathrm {\text {m}\text {V} }}$ with up to 5.1% energy efficiency. At a $20~ {\mathrm {\text {M}\text {Hz} }}$ pulse repetition rate, the transmitter consumes only $78~ {\mathrm {\mu \text {W} }}$ while producing -24.5dBm of output power. Measurement results confirm compliance with FCC regulations and suitability for deep implantation in biomedical applications. The design achieves a competitive Figure-of-Merit (FoM) of $0.017~({\mathrm {\text {m}\text {m} ^{2}}} \cdot {\mathrm {\text {p}\text {J} }}) / (\text {b} \cdot {\mathrm {\text {V}}})$ , demonstrating its scalability and efficiency compared to prior state-of-the-art solutions.