The trend toward energy self-sufficient probes and ever smaller mobile electronics systems continues unabated. They are used, for example, to monitor the status of the engines on airplanes, or for medical implants. They gather the energy they need for this from their immediate environment - from vibrations, for instance.
Fraunhofer researchers have developed a process for the economical production of piezoelectric materials. They will unveil a preliminary demonstration model at this year’s electronica trade show from November 11 to 14 in Munich (Hall A4, Booth 113).
Energy Harvesting Demonstrator
© Fraunhofer FEP | Picture in printable resolution: www.fep.fraunhofer.de/press
When there is little space, or an exchange is complicated, then power supply for sensors via battery or cable is most often too circuitous. The best approach is to have the energy intake integrated and highly durable. One solution is offered by Energy Harvesting – onsite power production for instance through solar cells, thermoelectric or piezoelectric materials.
Piezoelectric materials can convert mechanical vibrations into electric energy because the effect of mechanical force results in a charge separation. They can be applied in places where a defined but not necessarily constant state of vibration exists – on industrial equipment, for example, or airplane engines, in car engines or even on the human body, where blood pressure, breathing or heartbeat are constantly creating momentum.
Up to now, the piezoelectric material of choice has mainly been leadzirconium-titanium composites (PZT). Aluminum nitride (AlN) is another option. Compared to PZT, it possesses more favorable mechanical properties, is lead-free, more stable and biocompatible. Moreover, it is virtually no problem to integrate AlN layers into conventional manufacturing processes for microelectronics.
New process for manufacturing piezo coatings
Here’s the dilemma: In order to integrate piezoelectric materials into increasingly smaller electrical systems, they likewise have to be as small as possible – on the one hand. On the other hand, they need a certain volume in order to produce sufficient energy. So far it has been impossible to produce the targeted coatings in a manner that is economically feasible enough using the available methods to date.
Deposition rates, homogeneity and coating areas are too small. But now, scientists at Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP have developed a process by which they can precipitate highly homogeneous layers on diameters of up to 200 mm with simultaneously high deposition rates. Thus, the process is substantially more productive and profitable than previous processes.
The researchers deposited the layers by reactive magnetron sputtering of aluminum targets in an argon-nitrogen atmosphere onto a silicon wafer. With this physical procedure, atoms from solid bodies are discharged into the gas phase by bombarding the targets with highly energetic noble gas ions. They then deposit on the wafer as a layer. For this purpose, the Fraunhofer FEP scientists use the DRM 400, a double ring magnetron sputter source developed in-house that consists of two ring-shaped targets.
Since the discharges of both targets overlap, it is possible to deposit the AlN layers homogeneously onto a large coating surface with a piezo-coefficient d33 of up to 7 pC/N. The higher this figure, the more strongly the material reacts. The typical values described in available research literature for the piezo-coefficient d33 of AlN ranges between 5 to 7 pC/N. At the same time, the mechanical stress of the layers can be flexibly modified to the relevant field of application. These impact for example the adhesion strength of the coating, the electromechanical coupling and the values of the energy produced.
Boosting energy yields even further
Working in collaboration with the Technical University of Dresden and Oulu University in Finland, the Fraunhofer FEP researchers conducted tests on energy harvesting with AlN coatings on silicon strips measuring 6×1cm². For demonstrations, they were able to reach generated powers of several hundred μW.
According to project manager Stephan Barth, this figure admittedly cannot be transferred to a practical application at a 1:1 ratio, since the generated power depends on multiple factors: “On the one hand, the design – that is to say the layer thickness, transducer geometry, volume, space and substrate materials all have an impact; on the other hand, there is an effect from the vibrational behavior, such as frequency, amplitude or ambient medium and one should also keep in mind the necessity of the matching to the sensor electronics." Nonetheless, the AlN layers are a practicable alternative for operating low-power sensors, as they are used in industrial applications or with cardiac pacemakers.
In order to raise the power yield even higher, scientists are additionally using layers made from aluminum-scandium-nitride, which they deposit by reactive co-sputtering. Compared to pure AlN, these exhibit substantially higher piezo-coefficients with similar coating rates. This means three to four times more power is produced through this. Another future focus of the researchers’ work will be placed on optimization of the transducer design for power production. The goal would be to downsize the entire construction, to elevate capacities even further, and to better adapt resonance frequency to the respective application.
For further information
Stephan Barth | Phone +49 351 2586-379 | email@example.com
Organic Electronics, Electron Beam and Plasma Technology FEP| Phone +49 351 2586 452 | Annett.Arnold@fep.fraunhofer.de
Winterbergstraße 28 | 01277 Dresden | Germany | www.fep.fraunhofer.de
Annett Arnold | Fraunhofer-Institut
Did you know that specialty light sources are being used for water analysis?
22.03.2018 | Heraeus Noblelight GmbH
Neutrons pave the way to accelerated production of lithium-ion cells
20.03.2018 | Technische Universität München
Satellites in near-Earth orbit are at risk due to the steady increase in space debris. But their mission in the areas of telecommunications, navigation or weather forecasts is essential for society. Fraunhofer FHR therefore develops radar-based systems which allow the detection, tracking and cataloging of even the smallest particles of debris. Satellite operators who have access to our data are in a better position to plan evasive maneuvers and prevent destructive collisions. From April, 25-29 2018, Fraunhofer FHR and its partners will exhibit the complementary radar systems TIRA and GESTRA as well as the latest radar techniques for space observation across three stands at the ILA Berlin.
The "traffic situation" in space is very tense: the Earth is currently being orbited not only by countless satellites but also by a large volume of space...
An international team of researchers has discovered a new anti-cancer protein. The protein, called LHPP, prevents the uncontrolled proliferation of cancer cells in the liver. The researchers led by Prof. Michael N. Hall from the Biozentrum, University of Basel, report in “Nature” that LHPP can also serve as a biomarker for the diagnosis and prognosis of liver cancer.
The incidence of liver cancer, also known as hepatocellular carcinoma, is steadily increasing. In the last twenty years, the number of cases has almost doubled...
In just a few weeks from now, the Chinese space station Tiangong-1 will re-enter the Earth's atmosphere where it will to a large extent burn up. It is possible that some debris will reach the Earth's surface. Tiangong-1 is orbiting the Earth uncontrolled at a speed of approx. 29,000 km/h.Currently the prognosis relating to the time of impact currently lies within a window of several days. The scientists at Fraunhofer FHR have already been monitoring Tiangong-1 for a number of weeks with their TIRA system, one of the most powerful space observation radars in the world, with a view to supporting the German Space Situational Awareness Center and the ESA with their re-entry forecasts.
Following the loss of radio contact with Tiangong-1 in 2016 and due to the low orbital height, it is now inevitable that the Chinese space station will...
Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, provider of research and development services for OLED lighting solutions, announces the founding of the “OLED Licht Forum” and presents latest OLED design and lighting solutions during light+building, from March 18th – 23rd, 2018 in Frankfurt a.M./Germany, at booth no. F91 in Hall 4.0.
They are united in their passion for OLED (organic light emitting diodes) lighting with all of its unique facets and application possibilities. Thus experts in...
A new scenario seeking to explain how Mars' putative oceans came and went over the last 4 billion years implies that the oceans formed several hundred million...
23.03.2018 | Event News
19.03.2018 | Event News
16.03.2018 | Event News
23.03.2018 | Materials Sciences
23.03.2018 | Agricultural and Forestry Science
23.03.2018 | Physics and Astronomy