Human skin, the largest organ in our body, is a sensitive detector of both pressure and temperature. Efforts to develop similar sensors for electronics are widespread
A joint international research project of the Universities of Cambridge, Linz and Princeton, the Joanneum Weiz and the University of Applied Science Jena has resulted in a nanocomposite for electronic skin that can distinguish between pressure and heat just as can real skin. The bifunctional material features nanoparticles of the piezoelectric ceramic lead titanate embedded in a ferroelectric polymer that can be pressed into a film 30 µm thick. The polarizations of the two constituents can be configured independently.
The “Journal of Applied Physics” by the American “Institute of Physics” reported the research in its December 2009 Research Highlights in cooperation with the University of Applied Science Jena. The project is entitled “Flexible active-matrix cells with selectively poled bifunctional polymer-ceramic nanocomposite for pressure and temperature sensing skin.” The investigation links the research group around Professor Dr. Bernd Ploss, FH Jena, with 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, explains “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.
See also the “Physics Today” article from July 13th 2009:
Contact Information:
Prof. Dr. Bernd Ploss
Prof. Dr. Bernd Ploss
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Source: University of Applied Science Jena
Thema: Micro-Nano-Opto, New Materials and Chemistry
Thema: Micro-Nano-Opto, New Materials and Chemistry
