Vladimir Leonov

Thermoelectric Converters of Human Warmth for Self-Powered Wireless Sensor Nodes

Solar cells are the most commonly used devices in customer products to achieve power autonomy. This paper discusses a complementary approach to provide power autonomy to devices on a human body, i.e., thermoelectric conversion of human heat. In indoor applications, thermoelectric converters on the skin can provide more power per square centimeter than solar cells, particularly in adverse illumination conditions. Moreover, they work day and night. The first sensor nodes powered by human heat have been demonstrated and tested on people in 2004-2005. They used the state-of-the-art 100-muW watch-size thermoelectric wrist generators fabricated at IMEC and based on custom-design small-size BiTe thermopiles. The sensor node is completed with a power conditioning module, a microcontroller, and a wireless transceiver mounted on a watchstrap

Human++: autonomous wireless sensors for body area networks

This paper gives an overview of the results of BMECs Human++ research program. This program aims to achieve highly miniaturized and autonomous sensor systems that enable people to carry their personal body area network. The body area network will provide medical, lifestyle, assisted living, sports or entertainment functions. It combines expertise in wireless ultra-low power communications, packaging, 3D integration technologies, MEMS energy scavenging techniques and low-power design techniques.

Thermoelectric MEMS generators as a power supply for a body area network

Miniaturized and cost-effective thermoelectric generators (TEG) scavenging energy from environment could potentially provide power autonomy to consumer electronic products operating at low power. For example, TEG mounted in a wristwatch have been used to generate electricity from human heat. The key point of IMECs research in this field is the realization of a body area network, consisting of a set of wireless sensors/actuators, able to provide health, sports, comfort, and safety monitoring functions to the user. The development of miniature energy scavengers built on MEMS technology is a primary goal of the ongoing research, as this will make the network truly power autonomous. In this paper, the modeling and a novel design of MEMS TEG especially conceived for human body applications are described. The design is built on the basis of a thermal model of the device, which includes the human body as one of its important elements. For this purpose, the research on human body thermal features is performed. The TEG prototype made with commercial thermopiles is tested with power conditioning electronics and a wireless module mounted on a watchstrap.

Wearable electronics self-powered by using human body heat: The state of the art and the perspective

In this paper, we present our vision of what kind of wearable devices and how they can be powered by the heat of human beings and by using ambient light. The basic principles of designing body-powered devices and ways of their hybridizing with photovoltaic cells are discussed. The mechanisms of thermoregulation in humans and the laws of thermodynamics enable placing a distinct boarder between realistic targets and the science fiction. These allow prediction of application areas for wearable energy harvesters accounting for competitive batteries with long service life. The existing family of body-powered wearable devices and new technologies for thermopiles are discussed. The theory and practice point at the necessity of using microelectronic and microelectromechanical system technologies for the target application area. These technologies for thermopiles offer the possibility of reduced production cost. Therefore, autonomous systems powered thermoelectrically could be successfully marketed. The related as...

Human++: From technology to emerging health monitoring concepts

This paper gives an overview of the recent results from the Human++ research program, which targets the realization of miniaturized, intelligent and autonomous wireless sensor nodes for body area networks. It combines expertise in micro-power harvesting techniques, ultra-low-power radio, ultra-low-power DSP and sensors and actuators. This paper illustrates how technological breakthroughs in these areas lead to the emergence of new health monitoring concepts.

Human++: Emerging Technology for Body Area Networks

This paper gives an overview of results of the Human++ research program [1]. This research aims to achieve highly miniaturized and autonomous transducer systems that assist our health and comfort. It combines expertise in wireless ultra-low power communications, 3D integration technologies, MEMS energy scavenging techniques and low-power design techniques.

Body-Heat Powered Autonomous Pulse Oximeter

A wireless pulse oximeter for non-invasive measurement of pulse and blood oxygen saturation has been realized. The device is powered by a thermoelectric generator in the form of a watch using the persons body heat and therefore achieves full energy autonomy. It does not require a battery, only a small (super-)capacitor as a short-time energy buffer. At 22degC ambient temperature, the generator produces more than 100muW of electrical power. All signal processing is done locally in the sensor. To our knowledge, this is the first realization of a non-trivial biomedical sensor fully powered by the patients body heat.

A batch process micromachined thermoelectric energy harvester: fabrication and characterization

Micromachined thermopiles are considered as a cost-effective solution for energy harvesters working at a small temperature difference and weak heat flows typical for, e.g., the human body. They can be used for powering autonomous wireless sensor nodes in a body area network. In this paper, a micromachined thermoelectric energy harvester with 6 μm high polycrystalline silicon germanium (poly-SiGe) thermocouples fabricated on a 6 inch wafer is presented. An open circuit voltage of 1.49 V and an output power of 0.4 μW can be generated with 3.5 K temperature difference in a model of a wearable micromachined energy harvester of the discussed design, which has a die size of 1.0 mm × 2.5 mm inside a watch-size generator.

An electrostatic energy harvester with electret bias

We have designed, fabricated and characterized a MEMS electrostatic energy harvester using an electret as internal bias. The device operates in continuous mode and features a high voltage output, a large travelling distance of a big mass within a compact design using full bulk silicon thickness. The output power is about 1μW at an acceleration power spectral density of 0.03g2/Hz.

Technologies for highly miniaturized autonomous sensor networks

Recent results of the autonomous sensor research program HUMAN++ will be summarized in this paper. The research program aims to achieve highly miniaturized and (nearly) autonomous sensor systems that assist our health and comfort. Although the application examples are dedicated to human monitoring/assistance, the necessary technology development for this program is generic and can serve many wireless sensor applications. This multi-disciplinary program combines research on wireless ultra-low-power communications, research on 2D/3D integration and packaging platforms, energy scavenging techniques, as well as low-power and ultra-low-power sensor circuit design. An example sensor system is the wearable wireless EEG system.