Battery-free Operation Research Articles

InGaP/GaAs heterojunction photosensor powered by an on-chip GaAs solar cell for energy harvesting

In this study, an InGaP/GaAs heterojunction phototransistor (HPT) and a GaAs solar cell were monolithically integrated into an HPT epitaxial wafer, and the battery-free operation of the HPT was demonstrated for energy harvesting. Although the thickness and doping condition of the layers were optimized for the HPT performance, but not for the solar cell performance, the obtained short-circuit current was high enough to operate the InGaP/GaAs HPT in a two-terminal (2T) configuration. A collector photocurrent of 0.63 mA was obtained when the energy-harvesting InGaP/GaAs 2T-HPT was exposed to white light with a power density of 35 mW/cm2, and it linearly increased with the power density. For a potential application of the energy-harvesting InGaP/GaAs HPT as a photosensor in space, the device was irradiated with electrons of 1 MeV energy and 1015 cm−2 fluence. No significant degradation of the fabricated energy-harvesting 2T-HPT after the high-energy electron irradiation guarantees its battery-free operation in space.

A Closed-Loop Reconfigurable Switched-Capacitor DC-DC Converter for Sub-mW Energy Harvesting Applications

Energy harvesting is an emerging technology for powering wireless sensor nodes, enabling battery-free operation of these devices. In an energy harvesting sensor, a power management circuit is required to regulate the variable harvested voltage to provide a constant supply rail for the sensor circuits. The power management circuit needs to be compact, efficient, and robust to the variations of the input voltage and load current. A closed-form power expression and custom control algorithm for regulation of a switched-capacitor DC-DC converter with optimal conversion efficiency are proposed in this paper. The proposed regulation algorithm automatically adjusts both the voltage gain and switching frequency of a switched-capacitor DC-DC converter based on its input voltage and load current, increasing the power efficiency across a wide input voltage range. The design and simulation of a fully integrated circuit based on the proposed power managing approach is presented. This power management circuit has been simulated in a 0.25 μm standard CMOS process and simulation results confirm that with an input voltage ranging from 0.5 V to 2.5 V, the converter can generate a regulated 1.2 V output rail and deliver a maximum load current of 100 μA. The power conversion efficiency is higher than 74% across a wide range of the input voltage with a maximum efficiency of 83%.

Preliminary Validation of a New Magnetic Wireless Blood Pump

In general, a blood pump must be small, have a simple configuration, and have sufficient hydrodynamic performance. Herein, we introduce new mechanisms for a wireless blood pump that is small and simple and provides wireless and battery-free operation. To achieve wireless and battery-free operation, we implement magnetic torque and force control methods that use two external drivers: an external coil and a permanent magnet with a DC-motor, respectively. Power harvesting can be used to drive an electronic circuit for wireless monitoring (the observation of the pump conditions and temperature) without the use of an internal battery. The power harvesting will be used as a power source to drive other electronic devices, such as various biosensors with their driving circuits. To have both a compact size and sufficient pumping capability, the fully magnetic impeller has five stages and each stage includes four backward-curved blades. The pump has total and inner volumes of 20 and 9.8 cc, respectively, and weighs 52 g. The pump produces a flow rate of approximately 8 L/min at 80 mm Hg and the power generator produces 0.3 W of electrical power at 120 Ω. The pump also produces a minimum flow rate of 1.5 L/min and a pressure of 30 mm Hg for circulation at a maximum distance of 7.5 cm.

A Battery-Free Multichannel Digital Neural/EMG Telemetry System for Flying Insects

This paper presents a digital neural/EMG telemetry system small enough and lightweight enough to permit recording from insects in flight. It has a measured flight package mass of only 38 mg. This system includes a single-chip telemetry integrated circuit (IC) employing RF power harvesting for battery-free operation, with communication via modulated backscatter in the UHF (902-928 MHz) band. An on-chip 11-bit ADC digitizes 10 neural channels with a sampling rate of 26.1 kSps and 4 EMG channels at 1.63 kSps, and telemeters this data wirelessly to a base station. The companion base station transceiver includes an RF transmitter of +36 dBm (4 W) output power to wirelessly power the telemetry IC, and a digital receiver with a sensitivity of -70 dBm for 10⁻⁵ BER at 5.0 Mbps to receive the data stream from the telemetry IC. The telemetry chip was fabricated in a commercial 0.35 μ m 4M1P (4 metal, 1 poly) CMOS process. The die measures 2.36 × 1.88 mm, is 250 μm thick, and is wire bonded into a flex circuit assembly measuring 4.6 × 6.8 mm.

Battery-free Radio Frequency Identification (RFID) Sensors for Food Quality and Safety

Market demands for new sensors for food quality and safety stimulate the development of new sensing technologies that can provide an unobtrusive sensor form, battery-free operation, and minimal sensor cost. Intelligent labeling of food products to indicate and report their freshness and other conditions is one important possible application of such new sensors. This study applied passive (battery-free) radio frequency identification (RFID) sensors for the highly sensitive and selective detection of food freshness and bacterial growth. In these sensors, the electric field generated in the RFID sensor antenna extends from the plane of the RFID sensor and is affected by the ambient environment, providing the opportunity for sensing. This environment may be in the form of a food sample within the electric field of the sensing region or a sensing film deposited onto the sensor antenna. Examples of applications include monitoring of milk freshness, fish freshness, and bacterial growth in a solution. Unlike other food freshness monitoring approaches that require a thin film battery for operation of an RFID sensor and fabrication of custom-made sensors, the passive RFID sensing approach developed here combines the advantages of both battery-free and cost-effective sensor design and offers response selectivity that is impossible to achieve with other individual sensors.

Actuation of Novel Blood Pump by Direct Application of Rotating Magnetic Field

This paper presents a magnetic centrifugal pump, driven by an external rotating magnetic field, for use in artificial heart-assist blood pumps. The magnet rotor in the pump is synchronized to a rotating magnetic field, which then causes the fabricated impeller to produce a centrifugal force in the pump. Because the pump is driven by the direct application of an external rotating magnetic field, the proposed pump does not require a shaft or mechanical bearings. Thus, the proposed mechanism and external driving source give the pump the advantages of compact size; wireless, battery-free operation; heat-free operation; and minimal risk of bacterial infections. The pump weight, length, and diameter are 34 g, 35 mm, and 20 mm, respectively. The compact size and performance make the device suitable for use in pediatric cardiac assistance pumps.

Working Distance Comparison of Inductive and Electromagnetic Couplings for Wireless and Passive Underwater Monitoring System of Rinsing Process in Semiconductor Facilities

This paper reports a side-by-side comparison of two wireless and passive sensing systems: inductive and electromagnetic (EM) couplings for an application of in-situ and real-time monitoring of wafer cleanliness in the rinsing process at semiconductor/microelectromechanical system (MEMS) manufacturing facilities. A MEMS sensor is designed to measure the resistivity of water, corresponding to the ionic concentration, to evaluate the rinsing process inside the micro-features. The transponder, containing the MEMS sensor, receives power from an external interrogator, modulates the resistivity data, and emits back the modulated signal to the interrogator, in all wireless and battery-free operation. Two wireless systems based on inductive and EM couplings have been implemented on 4-inch glass wafers, maintaining the wafer form factor. Inductive coupling system has parasitic electric field coupling. The working distance of the inductive coupling system is attenuated in water and is likely limited by signal-to-noise ratio (SNR), while that of the EM coupling is primarily limited by the coupled power. Hence, inductive coupling is suitable for a short distance measurement that allows more sophisticated functionality with sufficient power, whereas EM coupling could be optimized for long distance detection but has a tight power budget. The implemented on-wafer wireless monitoring units achieve a working distance of 6 and 25 cm with a concentration resolution of less than 2% (4 ppb for a 200 ppb solution) for inductive and EM couplings, respectively.

A novel all-in-one magnetic pump and power harvester design for bio-medicalapplications

This paper presents a magnetic centrifugal pump with a magnetic power harvester(all-in-one system) for medical applications. The proposed pump is driven by an externalrotating magnetic field. To produce pressure and electrical power, an all-in-one deviceconsisting of a pump and a power harvester was designed. It consists of a multi-stageimpeller, a disc type NdFeB permanent magnet, and a fixed wound coil on the pumpcase. The rotation of the rotor creates a continuous flow of liquid through thepump, with a pressure head, and an electrical power is generated in the wound coilbecause of the rotating magnetic field. The maximum flow rate and pressure are5000 ml min−1 and16 kPa, respectively, at 100 Hz. These results meet the requirements of an artificial heart assistanceblood pump. Under these operating conditions, the harvested voltage can reach a maximum of8.2 Vp−p. With this configuration and control method, wireless and battery-free operation ispossible, which is required in the medical field. Moreover, the power harvester can monitorthe pump conditions without additional electrical power and can provide electrical power toother implanted electrical devices. The performances of the pump and powerharvester were verified in a laboratory experiment. Overall, the proposed systemacts as a pump and a power harvester that is fully wireless and battery-free.

Magnetic Robotics: A Biologically Inspired Walking Robot

In this paper, we introduce a biologically inspired walking robot and its biomimetic mechanism. The proposed magnetic robot is driven by a rotating magnetic field. The magnetic musculoskeletal structure (MMS) of the actuator produces magnetic torque within the rotating magnetic field. In addition, the rotating magnetic field provides wireless and battery-free operation to the micro-robot. The musculoskeletal structure of the human shoulder is developed by magnetic artificial muscles that consist of an NdFeB ball-type permanent magnet, 25 um polyimide thin film, and a metallic ring. Using the proposed system, we realized a new walking mechanism and walking robot for magnetic micro-robotics. The walking pattern depends on the direction of the magnetic torque between magnetic moment on the ball magnet and the rotating magnetic field. The direction of the magnetic moment is fixed. Therefore, the plane of the rotating magnetic field and the rotating direction are changed by an external joystick. This control method provides various walking performance such as turning, forward, and backward capabilities. The developed walking robot is analyzed through magnetics, biomechanics, and robotics. These various approaches can contribute development of the magnetic robotics.

Communication Concept for Sensors at an Inverter-Fed Electric Motor Utilizing Power-Line Communication and Energy Harvesting

In this paper, a novel communication concept for sensors at an inverter-fed electric motor is proposed. The concept utilizes power-line communication and a motor cable in data transmission. The signal used in communication is inductively coupled to the motor cable. The supply power for sensing and communication at the electric motor is harvested from the motor-phase conductor with a current-transformer-based power supply. The proposed concept has numerous advantages, such as no galvanic connection to the motor power circuit, an opportunity to implement the concept afterwards without electrical installation, and reliable and battery-free operation. The operation of the concept is analyzed, simulated, and verified by laboratory measurements.

Combinatorial Screening of Polymeric Sensing Materials Using RFID Sensors: Combined Effects of Plasticizers and Temperature

Recently, we have developed battery-free, passive RFID chemical and biological sensors that are attractive in diverse applications where sensor performance is needed at a low cost and when battery-free operation is critical. In this study, we apply this attractive low-cost sensing platform for the combinatorial screening of formulated sensing materials. As a model system, a 6 x 8 array of polymer-coated RFID sensors was constructed to study the combined effects of polymeric plasticizers and annealing temperature. A solid polymer electrolyte Nafion was formulated with five different phthalate plasticizers: dimethyl phthalate, butyl benzyl phthalate, di-(2-ethylhexyl) phthalate, dicapryl phthalate, and diisotridecyl phthalate. These sensing film formulations and control sensing films without a phthalate plasticizer were deposited onto 9-mm diameter RFID sensors, exposed to eight temperatures ranging from 40 to 140 degrees C using a gradient temperature heater, and evaluated for their response stability and gas-selectivity response patterns. This study demonstrated that our RFID-based sensing approach permits rapid cost-effective combinatorial screening of dielectric properties of sensing materials.

An Energy Management Circuit for Self-Powered Ubiquitous Sensor Modules Using Vibration-Based Energy

An energy management circuit is proposed for self-powered ubiquitous sensor modules using vibration-based energy. With the proposed circuit, the sensor modules work with low duty cycle operation. Moreover, a two-tank circuit as a part of the energy management circuit is utilized to solve the problem that the average power density of ambient energy always varies with time while the power consumption of the sensor modules is constant and larger than it. In addition, the long start-up time problem is also avoided with the timing control of the proposed energy management circuit. The CMOS implementation and silicon verification results of the proposed circuit are also presented. Its validity is further confirmed with a vibration-based energy generation. The sensor module is used to supervise the vibration of machines and transfer the vibration signal discontinuously. A piezoelectric element acts as the vibration-to-electricity converter to realize battery-free operation.