Here, we report advanced materials and devices that enable high-efficiency mechanical-to-electrical energy conversion from the natural contractile and relaxation motions of the heart, lung, and diaphragm, demonstrated in several different animal models, each of which has organs with sizes that approach human scales. A cointegrated collection of such energy-harvesting elements with rectifiers and microbatteries provides an entire flexible system, capable of viable integration with the beating heart via medical sutures and operation with efficiencies of ∼2%. Additional experiments, computational models, and results in multilayer configurations capture the key behaviors, illuminate essential design aspects, and offer sufficient power outputs for operation of pacemakers, with or without battery assist.

https://www.pnas.org/content/pnas/111/5/1927.full.pdf

Conformal piezoelectric energy harvesting and storage from motions of the heart, lung, and diaphragm

This paper presents a low power boost converter for thermoelectric energy harvesting that demonstrates an efficiency that is 15% higher than the state-of-the-art for voltage conversion ratios above 20. This is achieved by utilizing a technique allowing synchronous rectification in the discontinuous conduction mode. A low-power method for input voltage monitoring is presented. The low input voltage requirements allow operation from a thermoelectric generator powered by body heat. The converter, fabricated in a 0.13 μm CMOS process, operates from input voltages ranging from 20 mV to 250 mV while supplying a regulated 1 V output. The converter consumes 1.6 (1.1) μW of quiescent power, delivers up to 25 (175) μW of output power, and is 46 (75)% efficient for a 20 mV and 100 mV input, respectively.

A 20 mV Input Boost Converter With Efficient Digital Control for Thermoelectric Energy Harvesting

This paper presents a physically based model for the metal-oxide-semiconductor (MOS) transistor suitable for analysis and design of analog integrated circuits. Static and dynamic characteristics of the MOS field-effect transistor are accurately described by single-piece functions of two saturation currents in all regions of operation. Simple expressions for the transconductance-to-current ratio, the drain-to-source saturation voltage, and the cutoff frequency in terms of the inversion level are given. The design of a common-source amplifier illustrates the application of the proposed model.

An MOS transistor model for analog circuit design

The selection of drain current, inversion coefficient, and channel length for each MOS device in an analog circuit results in significant tradeoffs in performance. The selection of inversion coefficient, which is a numerical measure of MOS inversion, enables design freely in weak, moderate, and strong inversion and facilitates optimum design. Here, channel width required for layout is easily found and implicitly considered in performance expressions. This paper gives hand expressions motivated by the EKV MOS model and measured data for MOS device performance, inclusive of velocity saturation and other small-geometry effects. A simple spreadsheet tool is then used to predict MOS device performance and map this into complete circuit performance. Tradeoffs and optimization of performance are illustrated by the design of three, 0.18-mum CMOS operational transconductance amplifiers optimized for DC, balanced, and AC performance. Measured performance shows significant tradeoffs in voltage gain, output resistance, transconductance bandwidth, input-referred flicker noise and offset voltage, and layout area.

/pdf/tradeoffs-and-optimization-in-analog-cmos-design-2vmcctfb10.pdf

Tradeoffs and Optimization in Analog CMOS Design

Pythium insidiosum: an overview.

A recently proposed technique for enhancing near field, wireless energy transfer is to add resonant coils between the transmitter and the receiver. It also has the potential to provide a simple method for enhancing read range of near field radio frequency identification (RFID) systems. In spite of this, its application to the RFID context has not been, yet, deeply analyzed. This paper models and analyzes a half-duplex, frequency shift keying RFID system with one additional coil between the reader and the tag, considering both phases (charging and reading) of this bidirectional operation. A three-coil RFID system was designed using a commercial tag (RI-INL-R9QM widely used in cattle identification), reader (using a TMS3705), and the additional resonant coil (whose radius and quality factor were optimized). In addition, the influence of high coil quality factor is addressed for steady-state and transient response. The designed system increases almost $2.7 \times $ the original RFID read distance (from 16 to 43 cm). The analytical design and measurements data are in good agreement. The design procedure can be applied not only to other RFID systems but also to other systems that use the same channel to energize and transfer data, such as some implantable medical devices.

Bidirectional Analysis and Design of RFID Using an Additional Resonant Coil to Enhance Read Range

Arterial hypertension affects a quarter of the world’s population and is a major risk factor for cardiovascular disease. Blood pressure (BP) is one of the most relevant parameters used for continual monitoring of possible hypertension states in the elderly population. Furthermore, emerging evidence suggests that central blood pressure is a more accurate predictor of future cardiovascular events than brachial pressure, thus potentially providing a better hemodynamic determinant for clinical outcomes. This work presents a non-invasive Central (Aortic) blood pressure estimation method based on the pulse transit time (ptt) principle estimated from electrocardiogram (ECG) and ballistocardiogram (BCG) recordings. As the measured transit time presented takes place mainly within the aortic domain, we estimate aortic blood pressure instead of brachial pressure. Validation of the proposed method was performed with a small sample of healthy volunteers at a local gym. An Atcor Medical SphygmoCor device was used to monitor central and brachial blood pressure (systolic, mean, and diastolic) during rests of the strength maneuvers. Pulse transit time was estimated from ECG and BCG recordings and simultaneously recorded with all BP readings. Results showed that Systolic and Mean central blood pressures were most strongly correlated with ppt-estimated blood pressure in comparison to all other blood pressure readings; Bland-Altman plots showed an almost zero mean error (|μ|< 0.02mmHg) and bounded standard deviation σ< 5mmHg for all systolic and mean central BP readings. Experimental data, thus showed promissory results for monitoring aortic blood pressure via ptt. The scope of this pilot work is to provide initial validation of this method in order to develop a compact miniaturized device that allows the integration of wireless blood pressure monitoring into a wearable system.

Central blood pressure monitoring method oriented to wearable devices

A MOS-diode biased by a constant inversion level current source is a simple MOSFET-only circuit that implements a voltage source with a linear temperature dependence. Through adjustment of the inversion level, the temperature slope may be changed from negative to positive, including the constant voltage condition. A test circuit, fabricated on a 0.35μm CMOS technology, was measured from 300K to 375K while sweeping the inversion coefficient from 0.06 to 180. The theoretical model agrees with the measured data, accurately predicting the temperature slope. The presented all-region continuous model is especially useful at and near zero temperature slope operation.

A MOSFET-only voltage source with arbitrary sign adjustable temperature coefficient

The design of a binary ASK noncoherent demodulator circuit in CMOS technology is described. It will be used to decode an ASK signal carrying information from an external programming device to an implantable cardiac pacemaker. The cell , currently being fabricated, has a core die area of 0.29mm on a 2.4μm standard CMOS technology with 0.85V nominal threshold voltage. We review the characteristics of the signal and the specifications for the circuit. A non-standard topology is proposed, allowing the circuit to be fully integrated, thus, lowering the component count of the system and increasing reliabilit y. We detail the design to the transistor level with special consideration to the limitations associated with low supply voltage. We emphasize the careful sizing, using the (g m/ID) method, of transistors operating in the weak and moderate inversion regions. This allowed to lower the gate-source and saturation voltages, achieving operation for 2V even in the worst case condition of 1V maximum threshold voltage and 5 μA current consumption. We present simulation results and the cell l ayout for the proposed circuit and an alternative design. Finally, we draw some conclusions. An ASK Demodulator in CMOS Technology Marcelo Barú, Hugo Valdenegro, Conrado Rossi and Fernando Silveira Instituto de Ingeniería Eléctrica Universidad de la República J. Herrera y Reissig 565 Montevideo 11300 Uruguay Tel: +598 2 7110974 Fax: +598 2 7117435 E-mail: cabeza@iie.edu.uy

/pdf/an-ask-demodulator-in-cmos-technology-ybze6g6xrc.pdf

An ASK demodulator in CMOS technology

This paper presents a wide frequency range, ultra low power pulse generator based on a ring oscillator. The proposed architecture avoids the direct path current, reaching pulse frequencies down to the kHz range while maintaining the power consumption proportional to frequency. Furthermore, the used topology for the current starved inverter circuit improves the symmetry between rising and falling edges of the output signals of the ring oscillator with respect to the traditional implementation. A frequency range from 1.75kHz to 10MHz consuming 1nW and 3.6μW respectively was achieved in a 130nm CMOS process. The modular design can be used to generate any non-overlapping pulse sequence with variable width.

Fernando Silveira

Papers

Bidirectional Analysis and Design of RFID Using an Additional Resonant Coil to Enhance Read Range

Central blood pressure monitoring method oriented to wearable devices

A MOSFET-only voltage source with arbitrary sign adjustable temperature coefficient

An ASK demodulator in CMOS technology

Ultra low power pulse generator based on a ring oscillator with direct path current avoidance