This paper reports a microfabricated triaxial capacitive force sensor. The sensor is fully encapsulated with inert and biocompatible glass (fused silica) material. The sensor comprises two glass plates, on which four capacitors are located. The sensor is intended for subdermal implantation in fingertips and palms and providing tactile sensing capabilities for patients with paralyzed hands. Additional electronic components, such as passives and IC chips, can also be integrated with the sensor in a hermetic glass package to achieve an implantable tactile sensing system. Through attachment to a human palm, the sensor has been shown to respond appropriately to typical hand actions, such as squeezing or picking up a bottle.

Capacitive sensors are prevalent in IoT and healthcare devices due to their low cost and zero static power consumption. As a pivotal component in these devices, the sensor interface [1–4] poses distinct design challenges, especially in wireless systems with considerable channel loss. In this work, an interface IC is implemented for one such application, where it is combined with a force sensor to create a subcutaneous implant for tactile sensing. Through a sensor-brain interface, this device aims to help restore somatosensation, an important yet lacking function in the existing reanimation treatment of hand paralysis [4]. As illustrated in Fig. 17.10.1, the sensor device, intended for palm implantation, is controlled via a bidirectional inductive link with the primary coil worn on the wrist or affixed to the back of the hand, causing no interference with natural hand movements.

The sense of touch is critical to dexterous use of the hands and thus an essential component to efforts to restore hand function after amputation or paralysis. Prosthetic systems have focused on wearable tactile sensors. But wearable sensors are suboptimal for neuroprosthetic systems designed to reanimate a patient's own paralyzed hand. Here, we developed an implantable tactile sensing system intended for subdermal placement. The system is composed of a microfabricated capacitive force sensor, a custom integrated circuit supporting wireless powering and data transmission, and a laser-fused hermetic silica package. The miniature device was validated through simulations, benchtop testing, and ex vivo testing in a primate hand. The sensor implanted in the fingertip accurately measured skin forces with a resolution of 4.3 mN. The output from this novel sensor could be encoded in the brain with microstimulation to provide tactile feedback. More broadly, the materials, system design, and fabrication approach establish new foundational capabilities for various applications of implantable sensing systems.

Electrochemical detection is widely used in biosensing fields, such as medical diagnosis and health monitoring due to its real-time response and high accuracy.Both passive and active electrodes and the corresponding readout circuits have been continuously improved over the past decades.This article summarizes the redox reaction method, state-of-the-art electrode materials, and readout circuits based on the passive three-electrode.The redox-current-based readout circuits are widely used and developed toward multichannel high precision and low power consumption.In terms of active electrodes, this article reviews the development of field-effect transistors (FETs)-based electrochemical detection and readout circuits.In the past decade, the development of organic electrochemical transistors (OECTs) has also enabled more precise electrochemical detection.

Paralyzed individuals would benefit from brain-computer interface (BCI) systems that restore not just motor function but also tactile and proprioceptive feedback. Such feedback has been shown to be critical to motor performance. Intracortical microstimulation (ICMS) has often been employed to provide artificial sensory feedback. However, it remains a question of how best to encode the multidimensional nature of this information (e.g. location, intensity, frequency of tactile signals). This project explored encoding goal-directed error signals as a way to simplify the feedback. We used a behavioral paradigm with rats in which ICMS was used as a tunable error signal to direct the subjects to unseen goal locations. We found that with relatively little training, the rats performance in the task with ICMS feedback was statistically as good as with natural sensory feedback. The results provide a demonstration that multidimensional sensory feedback can be mapped to single goal-related encoded signal in certain behavioral contexts to decrease the cognitive burden associated with interpreting multiple ICMS-evoked percepts.

This book has presented the analysis and design of BMI systems. To the best of our knowledge, this is the first work dedicated to studying bidirectional closed-loop BMI systems. The main motivation of this work is the fact that many significantly meaningful neuroscience experiments, especially in freely behaving animals, cannot be conducted without custom designed bidirectional closed-loop BMIs. With the close collaboration between neuroscientists and engineers, this work was able to identify and address several important and practical issues in BMI systems’ design. The developed system has been successfully used in several animal experiments, resulting in significant new observations.

Presents the President’s message for this issue of the publication.

In this paper, a wireless electrogoniometer is described using a pair of ultra-wide band (UWB) wireless smart sensor nodes that are interfaced to low power 3-axis accelerometers. A high resolution SAR ADC as well as a low power asynchronous continuous sampling event-driven ADC are integrated for the digitization of the input signal under different operation modes. An anti-self-locking circuit is included in the asynchronous event-driven ADC to improve the robustness. A tri-channel UWB transceiver is designed particularly for the data transmission of the 3-axis accelerometers. A power consumption of 4.6pJ/bit is achieved for the transmitter at 10Mbps while operating under 1.2V power supply. The receiver power consumption can be as low as 0.32nJ/bit at 10Mbps under 1.8V supply. To demonstrate one application of the device, the electrogoniometer was used to quantify the in-vivo response of a somatosensory neuron to joint angle changes.

We demonstrate the design and fabrication of tilted micropillar arrays on wrinkled elastomeric poly(dimethylsiloxane) as a reversibly switchable optical window. Upon re-stretching the as-prepared (opaque) film to the original pre-strain, the grating color is restored and ∼ 30% transmittance is recovered. Further stretching beyond the pre-strain makes the film more transparent. This process is fully reversible and repeatable for many cycles.

The articles in this special issue focus on applications supported by bioinspired image processing.

In this paper, we report on an image sensor with an integrated focal-plane 2 × 2 wire-grid polarizer for the visible spectrum, fabricated in a 65-nm standard CMOS technology. This imager enables the reconstruction of the polarization response for each pixel. Finite-difference time-domain method has been used to optimize the extinction ratio (ER) in the visible spectrum of a multilayered focal-plane wire-grid polarizer. Experimental results show that an ER of 16.35 dB is achieved with a standard error of ~ 0.25% between the experimental results and the fitting sinusoidal polarization response curve. Design guidelines for the wire-grid polarizer are derived based on numerical analysis and experimental results. Sensitivity ratio is defined to balance the tradeoff between the intensity sensitivity and polarization sensitivity of the imager.

In this paper, a low-power, multifunctional CMOS smart sensor node is designed for an electronic facade, which provides an alternative solution to the concept of energy-efficient responsive buildings. Various sensing capabilities, including light intensity sensing, temperature sensing, motion tracking, and compressive image acquisition, are implemented on the sensor node. An 80 × 80 image pixel array is employed for motion tracking and compressive image acquisition. Various operational modes are realized, including: 1) event generation mode; 2) motion tracking mode; and 3) video output mode in full-resolution or compressed by the region of interest (ROI). A low-power, high-throughput motion detection algorithm is proposed in this paper. The power consumption of the proposed work is modeled, analyzed, and compared with traditional motion detection methods. According to numerical analysis, the throughput can be increased by 45% while using the proposed design instead of traditional temporal differential motion tracking methods with simislar power consumption. The proposed algorithm is realized by a pixel-level focal-plane motion detection unit, consisting of switched-capacitor circuit, analog memory, and dual-threshold comparator. The proposed design was fabricated in 0.5 μm 3M2P standard CMOS technology, occupying 3×3 mm 2 silicon area. The total power consumption is 17 μW, while the pixel array is performing motion tracking with a frame rate of 30 fps and a supply voltage of 3.3 V.

This paper presents a high efficiency, net-zero charge neural stimulator. A new stimulation strategy is proposed to reduce the charge error that originates from the irreversible charge diffusion, which is a common issue in traditional current matching stimulator designs. In addition, an arbitrary channel configuration of the working and counter electrodes is achieved. Two methodologies are applied to the proposed design to increase the stimulation efficiency: i) feedback control of an adaptive driving voltage, which enables a constant low operating voltage for the entire active circuits; ii) charge recycling, which “recycles” the accumulated charges on the blocking capacitor. An improved current mode DAC and a digital feed-forward error compensation comparator are integrated in the output stage to suppress the process variation, and minimize the charge error in continuous stimulation pulse trains. Performance characterization and invivo experimental result of a prototype chip fabricated in standard 180nm CMOS technology are presented. An efficiency improvement of 51% is measured in the experiment.