The use of Polyvinylidene Fluoride (PVDF) based piezoelectric nanofibers for sensing and actuation has been reported widely in the past. However, in most cases, PVDF piezoelectric nanofiber mats have been used for sensing applications. This work fundamentally characterizes a single electrospun PVDF nanofiber and demonstrates its application as a sensing element for nanoelectromechanical sensors (NEMS). PVDF nanofiber mats were spun by far field electrospinning (FFES) process and complete material characterization was conducted by means of scanning electron microscope (SEM) imaging, Raman Spectroscopy and FTIR spectroscopy. An optimized recipe was developed for spinning a single suspended nanofiber on a specially designed MEMS substrate which allows the nano-mechanical and electrical characterization of a single PVDF nanofiber. Electrical characterization is conducted using a single suspended nanofiber to determine the piezoelectric coefficient (d33) of the nanofiber to be -58.77 pm/V. Also the mechanical characterization conducted using a nanoindenter revealed a Young’s Modulus and hardness of 2.2 GPa and 0.1 GPa respectively. Finally, an application that utilizes the single PVDF nanofiber as a sensing element to form a NEMS flow sensor is demonstrated. The single nanofiber flow sensor is tested in presence of various oscillatory flow conditions.

We report a structure with 4 thin film layers composed of pure metal and dielectric materials and prepared by sputtering. The reflectance and transmittance are lower than 5% with the absorption to be achieved higher than 95% in the 400-1000nm wavelength region as match to the solar radiance spectrum. The thermal emittance of the structure is in the range of 0.063-0.10 through data analysis. The good reproducibility and stability of spectral data associated with the deposition process imply the advantage of the solar energy absorber which is cost-effective in application.

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This study reports a novel electrostatic vertical comb-drive micro-actuator (VCA) driven by the photovoltaic effect that results from the incident light. The vertical comb electrodes are composed of pn-junction structures (named PN-combs). The VCA with PN-combs can be driven by the photovoltaic effect and/or reverse electrical bias. The VCA with PN-combs was fabricated on an epitaxial silicon wafer and successfully driven by intensity-modulated laser light and reverse bias. The combination of the photovoltaic effect and reverse bias can further increase the mechanical scan angle of the VCA. Experiments demonstrate the feasibility of four driving methods, including optical driving, optical driving with DC reverse bias, electrical driving and electrical driving with DC photovoltaic voltage. KEYWORDSvertical comb-drive actuator, photovoltaic effect, electrostatic actuator.

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