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R2.03 - Piezo-Nano-Devices on Flexible Substrates: Challenges and Opportunities 
April 22, 2014   2:15pm - 2:45pm

Piezoelectric nanodevices can offer crucial advantages for energy harvesting, mechanical sensing/actuation, biomedical devices, optoelectronics, and more. In fact, in comparison with conventional piezoelectric materials, nanostructures can be highly deformed by tiny forces, exhibit outstanding mechanical properties, and can have substantially higher piezoelectric coefficients. However, many issues must be addressed, both at the theoretical and at the technological level, in order to design and fabricate optimal piezo-nano-devices on flexible substrates. In the first part of this presentation, I show how shape, electrical boundary conditions, position of contacts, type of mechanical input, and charge transport properties can all crucially affect the piezopotential, the mechanical-to-electrical conversion efficiency, and the on-off ratios of piezoelectric nanodevices. As an example, for a given mechanical input, laterally deflected cylindrical nanowires with total bottom contacts result in lower piezopotential and mechanical-to-electrical conversion efficiency than vertically compressed nanowires; as another example, the mechanical-to-electrical static conversion efficiency of vertically compressed nanowires is almost independent of strain at small strains and increases at higher strains, thus confirming that the ability of nanostructures to withstand extreme deformations without fracture may be a key for increasing the efficiency of nanogenerators. As another example, conical nanowires may prove advantageous for nanogenerators, piezotronics, and piezophototronics. In the second part I will highlight the challenges to overcome for taking full advantage of piezoelectric nanodevices on flexible substrates, with special reference to both modeling (e.g. parasitic impedances, transient phenomena, and scaling of the electro-mechanical properties, including the Young modulus and piezoelectric coefficients) and fabrication (e.g. low-temperature processing and complexity of in-liquids real-time monitoring). Finally, I will illustrate some piezoelectric nanodevices on flexible substrates.

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Keynote Address
Panel Discussion - Different Approaches to Commercializing Materials Research
Business Challenges to Starting a Materials-Based Company
Fred Kavli Distinguished Lectureship in Nanoscience
Application of In-situ X-ray Absorption, Emission and Powder Diffraction Studies in Nanomaterials Research - From the Design of an In-situ Experiment to Data Analysis