Bioelectronics Lab is the research lab of Dr. Hao Jiang. This lab is part of the School of Engineering at San Francisco State University. Dr. Jiang’s overarching research goals are to develop state-of-art memristor crossbar array based neuromorphic computing system as well as implantable circuits and systems for biomedical implants. The research activities in Dr. Jiang’s lab are summarized in the following:
Bio-inspired Neuromorphic Computing System
For implants that interfaces with neurons, a high-efficient miniaturized processor is highly desirable. Memristor based processor has demonstrated its potential to achieve high-efficient processing power with small factor; furthermore, the spike based neuromorphic computing scheme has the potential to exchange information with neuron systems directly, since both systems rely on electrical spikes to deliver information. In such a system, however, the high-speed read and write circuits pose major challenge to its overall efficiency. Dr. Jiang and his students actively look for new circuit architectures to achieve efficient read and write functions with maximal speed and minimal power and area. These circuits are different from traditional analog circuits because input and output signals swing from 0 to Vdd, also they are different from traditional digital circuits because the spacing time between any two spikes is a critical analog variable in the computation. A new breed of circuits is needed to achieve efficient signal processing with minimal power and area to meet implants’ requirements.
Passive Wireless Sensing
Passive wireless sensing system that only consists of an inductor and a sensing capacitor resonator is gaining popularity in medicine due to it simplicity and high-reliability. By wirelessly monitoring its resonant frequency, the variation of the capacitance that correlates to local in-vivo pressure or pH value can be extracted. The main challenge of a passive wireless sensing system is the trade off between the size of the coil and its maximal operating distance. By collaborating with Prof. Roy and Prof. Harrison in University of California at San Francisco (UCSF), Dr. Jiang and his students have developed a systematic approach to miniaturize the inductive coil yet maintaining the same operating distance.
Wireless Power Transfer
Biomedical implants demand more and more power to accommodate additional functionalities; however, the small size of an implant limits its battery capacity. Wireless power transfer can either charge the implant’s battery or support the implant’s activities by itself. The technology could significantly increase the implant’s functionality, improve its performance, and prolong its lifespan without dramatically increasing its size. The inductive-coupling based wireless power transfer using two face-to-face coils is an efficient way to deliver power wirelessly. Dr. Jiang and his students have developed a switching based rectifier that is able to efficiently boost and rectify the harvested low-voltage AC power to the usable high-voltage DC power.
Pulsed Ultra-Wide-Band (UWB) Circuits
Pulsed UWB is a desirable wireless communication protocol for implants. It needs much lower power for transmitting than for receiving, and its power consumption can dynamically correlate to the transmitting data rate. Both features are very desirable for implants. For most implants, reporting in-vivo data inside of the body to an external reader is one of the critical missions, and power is always scarce. Dr. Jiang and his collaborators explored several circuit design techniques to further reduce the power consumption of the pulse generator in its transmitter.