The integration of more advanced electronics technology into medical devices for patient monitoring, diagnosis and treatment continues at an ever-increasing rate, with new developments being announced daily. Among these significant technology breakthroughs are several advanced medical electronics circuit designs being presented at the upcoming 2014 Symposia on VLSI Technology & Circuits, scheduled for Honolulu from June 9-13.
Of particular note is a highlighted paper by researchers from the University of Washington that details a single-chip solution for a low-power, encrypted-signal wearable electrocardiography (ECG) system that enables secure cardiac monitoring on mobile devices such as smartphones or tablets. The chip is integrated into a form-fitting “smart shirt” that incorporates flexible electrodes, batteries and an antenna that interfaces with a clinical-standard 12-lead ECG to encrypt and wirelessly transmit the patient’s cardiac data via an on-chip ISM-band radio and flexible antenna, using less than 1mW.
Reference: Paper C18.4, “A Single-chip Encrypted Wireless 12-Lead ECG Smart Shirt for Continuous Health Monitoring,” T. Morrison et al., University of Washington.
Several other presentations at the Symposia highlight significant medical technology developments, including:
Wireless Power Transfer Technology
A 13.56MHz wireless power transfer system with a 1X/2X reconfigurable resonant regulating (R3) rectifier and wireless power control for biomedical implants will be presented by researchers from the Hong Kong University of Science & Technology. The system achieves output voltage regulation through two mechanisms – the local PWM loop of the secondary side controls the duty cycle of switching the rectifier between the 1X and 2X modes; and the duty cycle information
encoded in Manchester code is fed back wirelessly to the primary side using a novel backscattering uplink technique to adjust the transmitter power of the primary coil, adapting to load and coupling variations. The primary transmitter and the secondary R3 rectifier are fabricated in 0.35µm CMOS process, and exhibit a measured maximum received power and receiver efficiency of 102mW and 92.6%, respectively.
Reference: Paper C3.4, “A 13.56MHz Wireless Power Transfer System with Reconfigurable Resonant Regulating Rectifier and Wireless Power Control for Implantable Medical Devices,” X. Li, C.-Y. Tsui and W.H. Ki, HKUST
Non-Invasive Diagnostic Tools
Researchers from the Korea Advanced Institute of Science & Technology will present a paper highlighting a multi-modal spectroscopy IC that combines impedance spectroscopy (IMPS) and multi-wavelength near-infrared spectroscopy (mNIRS) as a proposed method for high-precision non-invasive glucose level estimation. A frequency sweep (10kHz-76kHz) sinusoidal oscillator (FSSO) is proposed for high resolution (500 steps) IMPS; while the proposed FSSO uses both linear digital frequency switching and continuous analog frequency sweep, with its output voltage swing stabilized by an adaptive gain control (AGC). The measurement results of IMPS and mNIRS are combined using an artificial neural network (ANN) in external smart device to enhance absolute relative difference (mARD) to 8.3% from 15% of IMPS, 15%-20% of mNIRS. The proposed 12.5mm2 0.18µm CMOS chip consumes peak power of 38mWat 1.5V.
Reference: Paper C13.1, “An Impedance and Multi-wavelength Near-infrared Spectroscopy IC for Non-invasive Blood Glucose Estimation,” K. Song, U. Ha, S. Park and H.-J. Yoo, KAIST
Ultra-sensitive Reactance Sensors for Dielectric Spectroscopy
A team of researchers from the University of California (Berkeley & San Francisco) will demonstrate a series of high-sensitivity reactance sensors at 6.5/11/17.5/30GHz for dielectric spectroscopy sensing on a single micron-size biological specimen. Signal-to-noise ratio is enhanced with the combination of interferometry and injection-locked oscillator sensors, while the offset incurred by chopping-ripple is reduced through ping-pong nested chopping. The sensors achieve a sensitivity of less than 1.25aF at 100kHz, enabling label-free cellular detection as a new analytical tool.
Reference: Paper C13.2, “A 6.5/11/17.5/30-GHz High Throughput Interferometer-based Reactance Sensors using Injection-Locked Oscillators and Ping-Pong Nested Chopping,” J.-C. Chien, M. Anwar*, E.-C. Yeh, L. Lee and A. Niknejad, University of California, Berkeley, *University of California, San Francisco
Ion-Image Sensor for DNA Sequencing
A 64x64 CMOS ion-image sensor for accurate high-throughput DNA sequencing will be demonstrated by researchers from the Nanyang Technological University. Dual-mode (pH/image) sensing is performed with ion-sensitive field-effect transistor (ISFET) fabricated using a standard CMOS image sensor (CIS) process. After addressing physical locations of DNA slices by optical contact imaging, local pH for one DNA slice can be mapped to its physical address with accurate correlation. Moreover, pixel-to-pixel ISFET threshold voltage mismatch is reduced by correlated double sampling (CDS) readout. Measurements show a sensitivity of 103.8mV/pH and fixed-pattern-noise (FPN) reduction from 4% to 0.3% with speed of 1200fps.
Reference: “Paper C13.3, “A 64×64 1200fps CMOS Ion-Image Sensor with Suppressed Fixed-Pattern-Noise for Accurate High-throughput DNA Sequencing,” X. Huang, F.Wang, J. Guo, M. Yan, H. Yu and K.S. Yeo, Nanyang Technological University
NMR-compliant Wirelessly Programmable Implant for Artificial Pancreas
Researchers from the University of Florida will demonstrate the design, implementation, and nuclear magnetic resonance (NMR) measurements for a wireless, magnetic compliant implant for the noninvasive monitoring of a bio-artificial pancreas post-implantation. The device increases NMR image signal sensitivity by 3.8dB and 2.6dB in 4.7T(200MHz) and 11.1T (470MHz) magnetic field strengths, respectively; and it supports sustained reliable operation through a strongly coupled resonance wireless powering scheme, in addition to improving high-resolution image SNR up to 73%.
Reference: Paper C13.4, “A 4.7T/11.1T NMR Compliant Wirelessly Programmable Implant for Bio-Artificial Pancreas In Vivo Monitoring,” W. Turner and R. Bashirullah, University of Florida
A team from University of California, Berkeley will present a 65nm CMOS 4.78mm2 integrated neuromodulation SoC. The device consumes just 417µW from a 1.2Vsupply while operating 64 acquisition channels with epoch compression at an average firing rate of 50Hz and engaging two stimulators with a pulse width of 250µs/phase, differential current of 150µA, and a pulse frequency of 100Hz. Compared to the state of the art, this represents the lowest area and power for the highest integration complexity achieved to date.
Reference: Paper C18.1, “A 4.78mm2 Fully-Integrated Neuromodulation SoC Combining 64 Acquisition Channels with Digital Compression and Simultaneous Dual Stimulation,” D. Yeager, W. Biederman, N. Narevsky, J. Leverett, R.Neely, J. Carmena, E. Alon and J. Rabaey, University of California, Berkeley
Low Power Neural Signal Recording
Researchers from the University of Michigan will demonstrate a low power, high efficiency neural signal recording amplifier with a novel multi-chopper technique implemented in 180nm CMOS. The input referred rms noise is 1.54µV (1-500Hz), with 266nA tail current and PSRR/CMRR of 92/89dB. The result corresponds to a 1.38 noise efficiency factor, which is the best reported among current state-of-the-art amplifiers.
Reference: Paper C18.2, “A 266nW Multi-Chopper Amplifier with 1.38 Noise Efficiency Factor for Neural Signal Recording,” Y.-P.Chen, D. Blaauw and D. Sylvester, University of Michigan
Implantable Glucose Monitoring Microsystem
California Institute of Technology researchers will demonstrate a fully implantable subcutaneous continuous glucose monitoring (CGM) microsystem on CMOS platform. The proposed design incorporates electrochemical sensing using an ultra-low-power potentiostatic system that is wirelessly powered through an inductive coupling at 900MHz and supports bidirectional data communication with an outside reader. A low-power potentiostat and an ADC record the on-chip sensor glucose readout. Pt and Ag/AgCl on-chip electrodes are post-fabricated and functionalized in situ by glucose oxidase enzyme to enable glucose measurement. The 1.4×1.4×0.25mm3 prototype, fabricated in a 0.18µm CMOS technology, was validated in glucose measurements, and exhibited a total system power consumption of 6µW.
Reference: Paper C18.3, “An Implantable Continuous Glucose Monitoring Microsystem in 0.18µm CMOS,” M.H. Nazari, M. Mujeeb-U-Rahman and A. Scherer, California Institute of Technology
Information about registration, Short Courses and technical abstracts of all accepted papers are available on the Symposia website.