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Helbling T.,greenTEG | Roman C.,ETH Zurich | Durrer L.,greenTEG | Stampfer C.,RWTH Aachen | Hierold C.,ETH Zurich
IEEE Transactions on Electron Devices | Year: 2011

Integrated piezoresitive strain gauges are established transducers for measuring displacements in microelectromechanical systems (MEMS). Due to large gauge factors (GFs) and low power operation and nanometer dimensions, carbon nanotubes (CNTs) are ideal candidates for further downscaling strain-gauge-based MEMS devices. Here, we present zero-level packaged strain gauges based on individual single-walled CNTs in a field-effect transistor configuration, which can be utilized as long-term stable and tunable transducers for measuring membrane deflections in ultraminiaturized pressure sensors. The gate electrode allows adjusting GFs of nanotube strain gauges by almost a factor of 10. Studies on nanotube segments of different lengths show highly reproducible GFs along the same CNT. The zero-level packaged pressure sensors show stable GFs over a period of at least 14 months. This paper is an important step toward reliable nanoscaled strain gauges with many potential applications, such as ultraminiaturized pressure-sensitive membranes or cantilever-based transducers. © 2011 IEEE.


Schwyter E.S.,ETH Zurich | Schwyter E.S.,greenTEG | Helbling T.,greenTEG | Glatz W.,greenTEG | Hierold C.,ETH Zurich
Review of Scientific Instruments | Year: 2012

A measurement setup is presented that allows for a complete and non-destructive material characterization of electrochemically deposited thermoelectric material. All electrical (Seebeck coefficient α, electrical conductivity σ), thermal (thermal conductivity λ), and thermoelectric (figure of merit ZT) material parameters are determined within a single measurement run. The setup is capable of characterizing individual electrochemically deposited Bi 2+xTe 3-x pillars of various size and thickness down to a few 10 μm, embedded in a polymer matrix with a maximum measurement area of 1 × 1 cm 2. The temperature range is limited to an application specific window near room temperature of 10 °C to 70 °C. A maximum thermal flux of 1 Wcm 2 can be applied to the device under test (DUT) by the Peltier element driven heat source and sink. The setup has a highly symmetric design and DUTs can be mounted and dismounted within few seconds. A novel in situ recalibration method for a simple, quick and more accurate calibration of all sensors has been developed. Thermal losses within the setup are analysed and are mathematically considered for each measurement. All random and systematic errors are encountered for by a MATLAB routine, calculating all the target parameters and their uncertainties. The setup provides a measurement accuracy of ±2.34 μVK for α, ±810.16 Sm for σ, ±0.13 WmK for λ, and ±0.0075 for ZT at a mean temperature of 42.5 °C for the specifically designed test samples with a pillar diameter of 696 μm and thickness of 134 μm, embedded in a polyethylene terephthalate polymer matrix. © 2012 American Institute of Physics.


Wojtas N.,ETH Zurich | Ruthemann L.,ETH Zurich | Glatz W.,greenTEG | Hierold C.,ETH Zurich
Renewable Energy | Year: 2013

There is a significant push to increase the output power of thermoelectric generators (TEGs) in order to make them more competitive energy harvesters. The thermal coupling of TEGs has a major impact on the effective temperature gradient across the generator and therefore the power output achieved. The application of micro fluidic heat transfer systems (μHTS) can significantly reduce the thermal contact resistance and thus enhance the TEG's performance. This paper reports on the characterization and optimization of a μTEG integrated with a two layer μHTS. The main advantage of the presented system is the combination of very low heat transfer resistances with small pumping powers in a compact volume. The influence of the most relevant system parameters, i.e. microchannel width, applied flow rate and the μTEG thickness on the system's net output performance are investigated. The dimensions of the μHTS/μTEG system can be optimized for specific temperature application ranges, and the maximum net power can be tracked by adjusting the heat transfer resistance during operation. A system net output power of 126mW/cm2 was achieved with a module ZT of 0.1 at a fluid flow rate of 0.07l/min and an applied temperature difference of 95K.It was concluded that for systems with good thermal coupling, the thermoelectric material optimization should focus more on the power factor than on the figure of merit ZT itself, since the influence of the thermal resistance of the TE material is negligible. © 2013 Elsevier Ltd.


PubMed | ETH Zurich and greenTEG
Type: | Journal: Scientific reports | Year: 2016

Light detection and quantification is fundamental to the functioning of a broad palette of technologies. While expensive avalanche photodiodes and superconducting bolometers are examples of detectors achieving single-photon sensitivity and time resolutions down to the picosecond range, thermoelectric-based photodetectors are much more affordable alternatives that can be used to measure substantially higher levels of light power (few kW/cm


Wojtas N.,ETH Zurich | Grab M.,ETH Zurich | Glatz W.,greenTEG | Hierold C.,ETH Zurich
Journal of Electronic Materials | Year: 2013

This study presents modeling and experimental results of micro thermoelectric generators (μTEGs) integrated into a multilayer micro heat exchange system. The multilayer configuration benefits from low heat transfer resistances at small fluid flow rates and at the same time from low required pumping powers. The compact stacked power device allows for high net output power per volume, and therefore a reduction in size, weight, and cost compared with conventional large-scale heat exchangers. The influence of the boundary conditions and the system design parameters on the net output power of the micro heat exchange system was investigated by simulation. The theoretical results showed a major impact of the microchannel dimensions and the μTEG thickness on the overall output performance of the system. By adapting the applied fluid flow rate, the system's net power output can be maximized for varying operating temperatures. Experimental measurements of the cross-flow micro heat exchange system were in good agreement with the performed simulations. A net μTEG output power of 62.9 mW/cm2 was measured for a double-layer system at an applied water inlet temperature difference of 60 K with a Bi 2Te3 μTEG (ZT of 0.12), resulting in a net volumetric efficiency factor of 37.2 W/m3/K2. © 2013 TMS.


Trademark
greenTEG | Date: 2010-10-25

Scientific and monitoring apparatus, namely, heat exchanger, heat flux sensor, thermoelectric converter; apparatus and instruments for conducting, transforming, regulating or controlling electricity, namely, electronic devices for generating electrical power from heat or water, thermoelectric heat pump and heat flux sensor, in International Class 9. Treatment of materials, namely, metal coating, deposition of semiconductor material by electrochemical deposition, in International Class 40. Scientific and technological services and research and design relating thereto; consultancy in connection with technology; industrial analysis and research services in International Class 42.


Trademark
greenTEG | Date: 2010-10-25

Scientific and monitoring apparatus, namely, heat exchanger, heat flux sensor, thermoelectric converter; apparatus and instruments for conducting, transforming, regulating and controlling electricity, namely, electronic devices for generating electrical power from heat or water, thermoelectric heat pump and heat flux sensor. Treatment of materials, namely, metal coating, deposition of semiconductor material by electrochemical deposition. Scientific and technological services and research and design relating thereto, namely, for integration of thermoelectric converter in devices for generation of electric power; consultancy in connection with process technology; industrial analysis and research services in the field of generating electrical power from heat or water.


Patent
greenTEG | Date: 2013-12-23

A heat flow sensor (WFS) and use thereof, which heat flow sensor should have the lowest possible invasiveness and nevertheless is robust enough to satisfy the requirements of individual applications. For this purpose, the heat flow sensor includes an active sensor element, which is provided with a highly thermally conductive heat-conducting element (8, 9) on the cold side and on the hot side, wherein the sensor element is covered or encased by an extremely thin, electrically strongly insulating, chemically inert, and strongly adhering protective layer (6).


greenTEG | Entity website

Norms and requirements What is the ISO 9869 norm? The ISO norm is established to secure the reliability of a heat flux measurement for investigating the thermal transmission properties of plain building components . If a measurement is conducted in line with ISO 9869, the measurement results can be considered as accurate ...


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