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Low Power High-Resolution Data Converters
The conventional analog frontend (AFE) design includes an instrumental amplifier (IA) followed by a medium-resolution ADC, which suffers from a limited dynamic range due to the high gain of the IA. As a result, artifacts can easily saturate the AFE, leading to corrupted EEG recordings. One potential solution to this issue is the ADC direct digitizing AFE, which employs a high-resolution ADC, such as a ΔΣ modulator, to significantly increase the dynamic range, making it capable of tolerating large artifacts.
2nd-order ΔΣM-based direct digitizing AFE (1×2 mm^2)
ASIC built into a head-mounted device
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Power Management Integrated Circuits for Energy Harvesting
The Internet of Medical Things (IoMT) records critical body signals, such as the electrocardiogram (ECG), enabling remote health monitoring and unlocking the potential to enhance patient safety and wellness. IoMT devices leverage high-efficient power management integrated circuits, which enable energy harvesting or the utilization of batteries for extended periods of operation. In this project, we designed a high-frequency switched-capacitor boost converter for body heat energy harvesting and a high voltage charge pump for ultrasonic energy harvesting.
Switch capacitor DC-DC converter (2×2.5 mm^2)
High voltage charge pump (2×2.5 mm^2)
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Low Power Data Radio
The backscatter communication technique has garnered increasing attention due to its capacity to provide ultra-low-power wireless connectivity. Backscatter-based transceivers facilitate passive connectivity by reflecting the incident wave. This allows for wireless connectivity without necessitating active RF blocks, providing a significant power efficiency advantage over conventional transceivers. Given the prevalence of WiFi as the dominant pervasive wireless network infrastructure in home and office environments, it is desirable to leverage backscatter modulation for low-power implementation and take advantage of existing WiFi networks for low-cost Internet connectivity.
Backscattering transmitter (1.1×1 mm^2)
Wakeup receiver (1.2×0.9 mm^2)
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Wirelessly Powered Sensor Interface System-on-Chip for IoMT Applications
In the field of bioelectrodes, there are several notable trends: increasing channel counts, closed-loop systems, and minimally invasive techniques. To address these trends, we have been developing wirelessly powered multimodal sensor interface System-on-Chips (SoCs). These SoCs are designed to integrate power management blocks, bidirectional radio, stimulation drivers, analog frontends, data converters, and control blocks into a single chip.
Optical and electrical stimulation (1×1 mm^2)
Multichannel recording and stimulation (3×5 mm^2)
Electrical stimulation (1×1.2 mm^2)
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Application 1: Closed-Loop Neural Interface Device for Locomotion Control
This project aims to understand how sensory neurons regulate interlimb coordination and gait selection using the cat model. We proposed to design a wirelessly powered, implantable, closed-loop neural interface device, capable of high-resolution mapping of activities of neurons in DRG and muscle electrical activities of selected muscles while selectively and reversibly manipulating sensory neurons in DRGs via optogenetic stimulation in a closed-loop manner.
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Application 2: Miniature Wirelessly-Powered Neural Interface Implants
There is an increasing realization that most of the brain function processes arise from a large network of neurons that are spread over different interconnected regions of the brain and interplay with each other, forming a complicated neural communication network. The next-generation neural interface is expected to have a distributed architecture that consists of large populations of wireless, miniature, power-efficient implants.
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Application 3: Self-Powered Health Monitoring Wearables
Many commercial and research devices have aimed to be able to measure ECG outside of the clinic. A major barrier to achieving long-lifetime and small form factor is the power source. Energy harvesting from a variety of sources, e.g., body heat, ambient light, and body motion, have become valid solutions, resulting in a variety of self-powered wearables. We propose low-power ASICs that harvest energy from thermoelectric generators and measure heart rate, respiratory rate, and body temperature.
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Application 4: Inductive Power Transmission System for High-Throughput Behavioral Studies
A significant number of behavioral neuroscience experiments are conducted on small freely moving rodents. These experiments tend to run for extended periods in large enough subject populations to increase the quality and statistical validity of the experiment results. We will design a rack-mountable wireless cage system to simplify the experiment routine of automatic data collection and wireless power delivery to mobile devices.
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Application 5: Ultrasound-Based Chronic Implantable Monitor
Ultrasonic wireless power transmission using pre-charged capacitive micromachined ultrasonic transducers (CMUT) is drawing great attention due to the easy integration of CMUT with CMOS techniques. We will design ASIC that interfaces with pre-charged CMUT to perform multiple tasks: wireless ultrasonic power receiving, wall-to-wall distance measurements, and transmitting measurements out.
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Application 6: Smart Data Acquisition System
To eliminate tethering effects on the small animals’ behavior during behavioral neuroscience experiments, such as neural interfacing, a robust and wideband wireless data link is needed for communicating with the wearable/implantable sensing elements without blind spots. We present a software-defined radio (SDR) based scalable data acquisition system, which can be programmed to provide coverage over standard-sized or customized experimental arenas.
