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Posted: December 18, 2009
A nanocomposite for electronic skin
(Nanowerk News) Joint research project of the Universities of Cambridge, Linz and Princeton, the Joanneum Weiz and the University of Applied Science Jena.
The Journal of Applied Physics by the American Institute of Physics currently lists a research paper in the Research Highlights section of its homepage that has been devised in cooperation with the University of Applied Science Jena: The “Flexible active-matrix cells with selectively poled bifunctional polymer-ceramic nanocomposite for pressure and temperature sensing skin” project has been developed by the research group around Professor Dr. Bernd Ploss, FH Jena, including research groups from Cambridge University, Johannes Kepler University Linz, Joanneum Research Weiz and Princeton University.
Dr. Bernd Ploss, Professor for physical metrology at the SciTec department, states on this: “Human skin is a sensitive detector of both pressure and temperature. Efforts to develop similar sensors for electronics are widespread, and many of the tools are already well-known. Piezoelectrical materials generate electrical signals in response to changes in applied pressure, and pyroelectrics are sensitive to changes in temperature.”
Unfortunately, almost all materials from each of those groups also fall into the other, which makes it difficult to discriminate between changes in pressure and temperature. However, the international team of researchers has come up with a nanocomposite that is able to differentiate between the two sensitivities.
Professor Ploss describes the material as follows: “Nanoparticles from lead titanium, embedded in a ferroelectric polymer, are the characteristic feature of this bifunctional material. Both components’ electric polarization can be configured independently. Thus, the polymer’s polarization can be oriented by alternating voltage with respect to the ceramic’s. When adjusting the polarizations parallel, the piezoelectric coefficients of the polymer and the ceramic cancel each other out, whereas the pyroelectric response is increased. When antiparallel, the material shows a piezoelectrical response only.
By selecting the phase of the last cycle of the AC voltage applied to different parts of their composite film, the scientists have defined areas sensitive to either pressure or temperature only. The films thus prepared have been mounted onto a flexible foil containing silicon or organic transistors. Initial results show linear responses of the pressure- and temperature-sensitive regions with only limited cross-sensitivities.