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.

In the context of IoT applications, together with the use of deep-submicron technologies as FinFET, this paper presents a revision of the gm/ID methodology for radio-frequency analog front-end circuits. Particularly, this methodology is applied for the design of LC-VCOs in the 5.8-GHz band using 20-nm FinFET transistors. To incorporate the FinFET model into the design flow, a semi-empirical model is extracted from electrical simulations. To show the good performance of the methodology, an LC-VCO design, picked from the calculated design maps, is electrically simulated, achieving good match regarding oscillation frequency and phase noise.

/pdf/all-inversion-region-g-m-i-d-methodology-for-rf-circuits-in-yoee2l0b6d.pdf

All-inversion region g m /I D methodology for RF circuits in FinFET technologies

The threat of viral influenza infections has sparked research efforts to develop vaccines that can induce broadly protective immunity with safe adjuvants that trigger robust immune responses. Here, we demonstrate that subcutaneous or intranasal delivery of a seasonal trivalent influenza vaccine (TIV) adjuvanted with the Quillaja brasiliensis saponin-based nanoparticle (IMXQB) increases the potency of TIV. The adjuvanted vaccine (TIV-IMXQB) elicited high levels of IgG2a and IgG1 antibodies with virus-neutralizing capacity and improved serum hemagglutination inhibition titers. The cellular immune response induced by TIV-IMXQB suggests the presence of a mixed Th1/Th2 cytokine profile, antibody-secreting cells (ASCs) skewed toward an IgG2a phenotype, a positive delayed-type hypersensitivity (DTH) response, and effector CD4+ and CD8+ T cells. After challenge, viral titers in the lungs were significantly lower in animals receiving TIV-IMXQB than in those inoculated with TIV alone. Most notably, mice vaccinated intranasally with TIV-IMXQB and challenged with a lethal dose of influenza virus were fully protected against weight loss and lung virus replication, with no mortality, whereas, among animals vaccinated with TIV alone, the mortality rate was 75%. These findings demonstrate that TIV-IMXQB improved the immune responses to TIV, and, unlike the commercial vaccine, conferred full protection against influenza challenge.

/pdf/quillaja-brasiliensis-nanoparticle-adjuvant-formulation-1d2vkwy4.pdf

Quillaja brasiliensis nanoparticle adjuvant formulation improves the efficacy of an inactivated trivalent influenza vaccine in mice

This paper presents a comprehensive review of state-of-the-art, commercially available neurostimulators. We analyse key design parameters and performance metrics of 45 implantable medical devices across six neural target categories: deep brain, vagus nerve, spinal cord, phrenic nerve, sacral nerve and hypoglossal nerve. We then benchmark these alongside modern cardiac pacemaker devices that represent a more established market. This work studies trends in device size, electrode number, battery technology (i.e., primary and secondary use and chemistry), power consumption and longevity. This information is analysed to show the course of design decisions adopted by industry and identifying opportunity for further innovation. We identify fundamental limits in power consumption, longevity and size as well as the interdependencies and trade-offs. We propose a figure of merit to quantify volumetric efficiency within specific therapeutic targets, battery technologies/capacities, charging capabilities and electrode count. Finally, we compare commercially available implantable medical devices with recently developed systems in the research community. We envisage this analysis to aid circuit and system designers in system optimisation and identifying innovation opportunities, particularly those related to low power circuit design techniques.

Trends in Volumetric-Energy Efficiency of Implantable Neurostimulators: A Review From a Circuits and Systems Perspective

A model for active resonators based on active inductors implemented with gyrator-C structure is proposed. The model includes transcapacitive effects between the gyrator ports, needed for accurately modeling transistor level implementation in nanometer process. The main trade-offs (quality factor, noise, linearity) are visualized based on the model. The limits to maximum Q and strategies to decrease noise are shown and validated by simulation on a case study of a 50 Ω 2.4 GHz resonator on a 28 nm FD-SOI process that achieves less noise than its passive counterpart with a consumption of 2.1 mA from a 1 V power supply.

Active inductors modelling and trade-offs reexamined

A simple technique for on-chip tuning of ultra low power Gm-C filters is analyzed in this paper. The technique locks the filter Gm/C2? frequency to an external reference clock. The proposed tuning method is tested with a low frequency first order high pass section. The tuning of this filter for different applications by changing the reference frequency is also explored. The circuit tunes the filter frequency in a range from 10 Hz to 200 Hz with a consumption of less than 800 nA.

Fernando Silveira

Papers

All-inversion region g m /I D methodology for RF circuits in FinFET technologies

Quillaja brasiliensis nanoparticle adjuvant formulation improves the efficacy of an inactivated trivalent influenza vaccine in mice

Trends in Volumetric-Energy Efficiency of Implantable Neurostimulators: A Review From a Circuits and Systems Perspective

Active inductors modelling and trade-offs reexamined

Ultra low power automatic tuning for gm-C filters