Bioelectronic Sensor Nodes for Internet of Bodies

Energy-efficient sensing with Physically-secure communication for bio-sensors on, around and within the Human Body is a major area of research today for development of low-cost healthcare, enabling continuous monitoring and/or secure, perpetual operation. These devices, when used as a network of nodes form the Internet of Bodies (IoB), which poses certain challenges including stringent resource constraints (power/area/computation/memory), simultaneous sensing and communication, and security vulnerabilities as evidenced by the DHS and FDA advisories. One other major challenge is to find an efficient on-body energy harvesting method to support the sensing, communication, and security sub-modules. Due to the limitations in the harvested amount of energy, we require reduction of energy consumed per unit information, making the use of in-sensor analytics/processing imperative. In this paper, we review the challenges and opportunities in low-power sensing, processing and communication, with possible powering modalities for future bio-sensor nodes. Specifically, we analyze, compare and contrast (a) different sensing mechanisms such as voltage/current domain vs time-domain, (b) low-power, secure communication modalities including wireless techniques and human-body communication, and (c) different powering techniques for both wearable devices and implants.Comment: 30 pages, 5 Figures. This is a pre-print version of the article which has been accepted for Publication in Volume 25 of the Annual Review of Biomedical Engineering (2023). Only Personal Use is Permitte

A brain-spinal interface (BSI) system-on-chip (SoC) for closed-loop cortically-controlled intraspinal microstimulation

This paper reports on a fully miniaturized brain-spinal interface system for closed-loop cortically-controlled intraspinal microstimulation (ISMS). Fabricated in AMS 0.35 µm two-poly four-metal complementary metal–oxide–semiconductor technology, this system-on-chip measures ~ 3.46 mm × 3.46 mm and incorporates two identical 4-channel modules, each comprising a spike-recording front-end, embedded digital signal processing (DSP) unit, and programmable stimulating back-end. The DSP unit is capable of generating multichannel trigger signals for a wide array of ISMS triggering patterns based on real-time discrimination of a programmable number of intracortical neural spikes within a pre-specified time-bin duration via thresholding and user-adjustable time–amplitude windowing. The system is validated experimentally using an anesthetized rat model of a spinal cord contusion injury at the T8 level. Multichannel neural spikes are recorded from the cerebral cortex and converted in real time into electrical stimuli delivered to the lumbar spinal cord below the level of the injury, resulting in distinct patterns of hindlimb muscle activation

Suppressing quantum errors by scaling a surface code logical qubit

Practical quantum computing will require error rates that are well below what is achievable with physical qubits. Quantum error correction offers a path to algorithmically-relevant error rates by encoding logical qubits within many physical qubits, where increasing the number of physical qubits enhances protection against physical errors. However, introducing more qubits also increases the number of error sources, so the density of errors must be sufficiently low in order for logical performance to improve with increasing code size. Here, we report the measurement of logical qubit performance scaling across multiple code sizes, and demonstrate that our system of superconducting qubits has sufficient performance to overcome the additional errors from increasing qubit number. We find our distance-5 surface code logical qubit modestly outperforms an ensemble of distance-3 logical qubits on average, both in terms of logical error probability over 25 cycles and logical error per cycle ($2.914\%\pm 0.016\%$ compared to $3.028\%\pm 0.023\%$). To investigate damaging, low-probability error sources, we run a distance-25 repetition code and observe a $1.7\times10^{-6}$ logical error per round floor set by a single high-energy event ($1.6\times10^{-7}$ when excluding this event). We are able to accurately model our experiment, and from this model we can extract error budgets that highlight the biggest challenges for future systems. These results mark the first experimental demonstration where quantum error correction begins to improve performance with increasing qubit number, illuminating the path to reaching the logical error rates required for computation.Comment: Main text: 6 pages, 4 figures. v2: Update author list, references, Fig. S12, Table I

Non-Abelian braiding of graph vertices in a superconducting processor

Indistinguishability of particles is a fundamental principle of quantum mechanics. For all elementary and quasiparticles observed to date - including fermions, bosons, and Abelian anyons - this principle guarantees that the braiding of identical particles leaves the system unchanged. However, in two spatial dimensions, an intriguing possibility exists: braiding of non-Abelian anyons causes rotations in a space of topologically degenerate wavefunctions. Hence, it can change the observables of the system without violating the principle of indistinguishability. Despite the well developed mathematical description of non-Abelian anyons and numerous theoretical proposals, the experimental observation of their exchange statistics has remained elusive for decades. Controllable many-body quantum states generated on quantum processors offer another path for exploring these fundamental phenomena. While efforts on conventional solid-state platforms typically involve Hamiltonian dynamics of quasi-particles, superconducting quantum processors allow for directly manipulating the many-body wavefunction via unitary gates. Building on predictions that stabilizer codes can host projective non-Abelian Ising anyons, we implement a generalized stabilizer code and unitary protocol to create and braid them. This allows us to experimentally verify the fusion rules of the anyons and braid them to realize their statistics. We then study the prospect of employing the anyons for quantum computation and utilize braiding to create an entangled state of anyons encoding three logical qubits. Our work provides new insights about non-Abelian braiding and - through the future inclusion of error correction to achieve topological protection - could open a path toward fault-tolerant quantum computing

Single-chip wireless microsystems for multichannel neural biopotential recording.

This project has developed single-chip low-power wireless microsystems, fabricated using a 1.5-mum double-poly double-metal n-well standard CMOS process, that can be used with micromachined recording microelectrode arrays for interfacing with the nervous system at the cellular level in unrestrained biological hosts. In particular, an ultralight 2-channel hybrid backpack telemeter is developed for muscle biopotential recording in small insects. It dissipates 2mW of power from a 3-V power supply, weighing only 0.74g (including two miniature batteries) that is light enough to be carried by air-borne moths. This system has been successfully employed for wireless in vivo recording of EMG biopotentials in a male giant sphinx moth Manduca Sexta over a transmission range of ∼2m. Two wireless battery-powered recording systems-on-a-chip (SOC) for multichannel neural interfacing have been developed that combine ac amplification, dc baseline stabilization, clock generation, time-division multiplexing, and wireless FM transmission of muV- and mV-range input biopotentials on chips interfaced with only three off-chip components. The 4-channel recording device measures 1.7 x 1.2 x 0.16cm3 and weighs 1.1g including two miniature batteries whereas the 8-channel recording system measures 2.1 x 2.1 x 0.16cm3 and weighs 2.2g. They dissipate in vitro tests in saline using two different neural recording microelectrodes. Successful single-channel wireless in vivo recordings of neural activity in the auditory cortex of an awake marmoset monkey have been performed at 96.2MHz at several transmission ranges up to 0.5m with measured SNR >8.4dB. Finally, a telemetry command receiver integrated with a multichannel neural recording transmitter is developed for wireless site selection and site monitoring within a 4.6 x 4.6-mm2 bi-directional biotelemetry chip. The receiver is designed to select seven recording sites from a total of 28 available sites according to four pre-defined site selection patterns and to perform power management via a 1-MHz Manchester-encoded ASK link. Detailed system simulation results together with preliminary measurement results from a fabricated prototype receiver are presented.Ph.D.Applied SciencesBiomedical engineeringElectrical engineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/125452/2/3192731.pd

Introduction to the Special Issue on the 2020 IEEE International Solid-State Circuits Conference (ISSCC)

It is an annual tradition ever from the start of the IEEE Journal of Solid-State Circuits (JSSC) in 1966 to publish extended manuscripts of a selected set of papers presented at the annual International Solid-State Circuits Conference (ISSCC). In this November issue, you will find selected papers from the Imagers, Medical, MEMS, and Displays (IMMD) and the Technology Directions (TD) sessions. Most of the bio-related papers are covered in these topics. Next month, the sessions of Analog, Power Management, Data Converters, RF, and Wireless will be covered, and in January, you will find the selected papers from the Wireline, Digital Circuits, Digital Architectures and Systems, Memory, and Machine Learning subcommittees