Frost & Sullivan Recognizes Holst Centre and imec for Its Path Breaking Wearable Energy Harvester Technology

Recently, Holst Centre and imec developed miniaturized health monitoring systems, which consume heat naturally dissipated from the human body in order to operate. While wearable devices that operate using the body’s heat have been in use for several years, small thermoelectric energy generators have so far proven their capability to power only small personal devices such as watches without needing an external power source. The unique device developed by Holst Centre and imec is the result of clever design of a thermal harvester, matched specifically to a human body, as well as a large reduction of the power consumption of the electronics. The thermal harvester is made of a thermoelectric material, in this case bismuth telluride, that converts human body heat into electric current. Once this device is placed close to the body, it generates electricity that is further accumulated in an energy storage system. The electricity capacitor subsequently powers the autonomous wearable electrocardiography (ECG) system and a radio which transmits the ECG signal real-time to a base station. Thanks to clever optimization, the power consumption of the electronics has been largely reduced. The thickness of the system components does not exceed 6.5 mm and can be easily integrated into fabric. Once installed, the system requires no technical maintenance.



“The personal devices, which couldn’t be made portable due to their large sizes or high power requirements can now be developed in the form of easy to wear and care gadgets,” says Frost & Sullivan Research Analyst Krzysztof Grzybowski. “This approach is valid for monitoring systems and related personal low-power appliances that could be integrated in clothes, e.g watches. On the other hand, devices like mobile phones currently still use too much power to be powered by body heat.



Holst Centre and imec’s demonstrated energy harvesting solution provides tens of microwatts of energy per square centimetre of the skin for modules with 3x4 cm2 dimensions. In this specific application, the energy harvesting module efficiency was sufficient to operate the wearable ECG using fourteen units integrated in a shirt and occupying less than 1.5 per cent of its total area. The device operation was tested in indoor and outdoor conditions with outdoor clothes worn on and off. During energy harvesting, the power management unit of the presented system uses the ASIC converter to charge two 2.4V batteries, which are powering the second stage DC/DC converter supplying the ECG unit. In all cases, the system performance was sufficient to operate the ECG.



Further, the whole unit is fortified against the mechanical stress that would accidentally destroy the fragile thermopiles of the energy harvester. The shock protection, made of thermally isolating material, is placed between the radiator and the hot end of the device (exposed to the source of a heat). It was found that this protection facilitates even washing the device in laundry with a drying cycle of 1,000 rpms. Interestingly, the developed prototype is service-free for its entire life and user activity is only limited to the need of wearing it. Once placed close to the body the device starts itself and monitors the patient’s health.



“Most personal devices still consume large amounts of energy that cannot be provided by currently available energy harvesting solutions,” notes Krzysztof Grzybowski. “However, increasing efficiencies of energy harvesters, such as the system developed by Holst Centre and imec for health monitoring systems, combined with a further decrease of power consumption of the electronic elements could enable the fabrication of a wide range of self sustainable personal solutions in the future.”



Holst Centre and imec will continue to miniaturize self-powered health monitoring devices such as this one through decreasing their power consumption. Maintenance-free devices, self-powered for their entire service life such as the demonstrated electrocardiograph in a shirt, allow for efficient and easy monitoring of human health, which was not possible in the past. In recognition of this unique wearable energy harvesting technology based on a unique design platform, Frost & Sullivan is proud to present Holst Centre and imec with the 2009 European Technology Innovation Award in the wearable energy harvesters market.



Each year, Frost & Sullivan presents this award to a company that has carried out new research, which has resulted in innovations that have or are expected to bring significant contributions to the industry in terms of adoption, change, and competitive posture. The award recognizes the quality and depth of a company’s research and development program as well as the vision and risk-taking that enabled it to undertake such an endeavour.



Frost & Sullivan Best Practices Awards recognize companies in a variety of regional and global markets for demonstrating outstanding achievement and superior performance in areas such as leadership, technological innovation, customer service, and strategic product development. Industry analysts compare market participants and measure performance through in-depth interviews, analysis, and extensive secondary research in order to identify best practices in the industry.