Integrating quantitative and qualitative methodologies to build a national R&D plan using data envelopment analysis based on R&D stakeholders' perspectives.

The yearly increase in government R&D investment and top-down national R&D investment allocation requires a more quantitative decision-making system that maximizes R&D performance and efficient budget allocation. Sound decision-making is necessary at both the selection stage and the pursuit stage in order to maximize limited national R&D resources. We study Korean smart farms as an example to examine national R&D investment from the various R&D actors (academia, industry, and research institutes) perspectives.

Affordance-Based Surgical Design Methods Considering Biomechanical Artifacts.

Surgical design in personalized medicine is often based on native anatomy, which may not accurately reflect the interaction between native musculoskeletal tissues and biomechanical artifacts. To overcome this problem, researchers have developed alternative methods based on affordance-based design. The design process can be viewed in terms of action possibilities provided by the (biological) environment.

Buckled MEMS Beams for Energy Harvesting from Low Frequency Vibrations.

Vibration energy harvesters based on the resonance of the beam structure work effectively only when the operating frequency window of the beam resonance matches with the available vibration source. None of the resonating MEMS structures can operate with low frequency, low amplitude, and unpredictable ambient vibrations since the resonant frequency goes up very high as the structure gets smaller. Bistable buckled beam energy harvester is therefore developed for lowering the operating frequency window below 100Hz for the first time at the MEMS scale.

Energy Harvesting Combat Boot for Satellite Positioning.

Most portable electronic devices are power-limited by battery capacity, and recharging these batteries often interrupts the user's experience with the device. The product presented in this paper provides an alternative to powering portables by converting regular human walking motion to electricity. The device harvests electric power using air bulbs, distributed in the sole of a shoe to drive a series of micro-turbines connected to small DC motors.

Investigation of plasmon resonance in metal/dielectric nanocavities for high-efficiency photocatalytic device.

Photocatalytic nanostructures loaded with metallic nanoparticles are being considered as a potential candidate for designing efficient water splitting devices. Here, we aim to unveil the plasmonic behavior of a device made of Au-TiO nanostructures through in-depth investigations combining electron energy loss spectroscopy (EELS) and cathodoluminescence (CL). The experiments confirm the existence of Au bulk plasmon excitation, intrinsic interband transitions, and plasmon losses over a wide range of energies (0.

Effect of anisotropic electron momentum distribution of surface plasmon on internal photoemission of a Schottky hot carrier device.

We recently reported that an Au/TiO photonic crystal device for photochemical energy conversion showed a sub-bandgap photoresponse centered at the surface plasmon polariton (SPP) resonant wavelength of this device. Here we developed a theoretical modeling of the internal photoemission in this device by incorporating the effects of anisotropic hot electron momentum distribution caused by SPP. The influences of interband and intraband transition, anisotropic momentum distribution of hot electrons by SPP are integrated to model the internal quantum efficiency (IQE) of this device.

Surface plasmon assisted hot electron collection in wafer-scale metallic-semiconductor photonic crystals.

Plasmon assisted photoelectric hot electron collection in a metal-semiconductor junction can allow for sub-bandgap optical to electrical energy conversion. Here we report hot electron collection by wafer-scale Au/TiO metallic-semiconductor photonic crystals (MSPhC), with a broadband photoresponse below the bandgap of TiO. Multiple absorption modes supported by the 2D nano-cavity structure of the MSPhC extend the photon-metal interaction time and fulfill a broadband light absorption.

Extremely Elastic Wearable Carbon Nanotube Fiber Strain Sensor for Monitoring of Human Motion.

The increasing demand for wearable electronic devices has made the development of highly elastic strain sensors that can monitor various physical parameters an essential factor for realizing next generation electronics. Here, we report an ultrahigh stretchable and wearable device fabricated from dry-spun carbon nanotube (CNT) fibers. Stretching the highly oriented CNT fibers grown on a flexible substrate (Ecoflex) induces a constant decrease in the conductive pathways and contact areas between nanotubes depending on the stretching distance; this enables CNT fibers to behave as highly sensitive strain sensors.

Direct Insulation-to-Conduction Transformation of Adhesive Catecholamine for Simultaneous Increases of Electrical Conductivity and Mechanical Strength of CNT Fibers.

Increase in conductivity and mechanical properties of a carbon nanotube (CNT) fiber inspired by mussel-adhesion chemistry is described. Infiltration of polydopamine into an as-drawn CNT fiber followed by pyrolysis results in a direct insulation-to-conduction transformation of poly(dopamine) into pyrolyzed-poly(dopamine) (py-PDA), retaining the intrinsic adhesive function of catecholamine. The py-PDA enhances both the electrical conductivity and the mechanical strength of the CNT fibers.

Experiment and simulation validated analytical equivalent circuit model for piezoelectric micromachined ultrasonic transducers.

An analytical Mason equivalent circuit is derived for a circular, clamped plate piezoelectric micromachined ultrasonic transducer (pMUT) design in 31 mode, considering an arbitrary electrode configuration at any axisymmetric vibration mode. The explicit definition of lumped parameters based entirely on geometry, material properties, and defined constants enables straightforward and wide-ranging model implementation for future pMUT design and optimization. Beyond pMUTs, the acoustic impedance model is developed for universal application to any clamped, circular plate system, and operating regimes including relevant simplifications are identified via the wave number-radius product ka.

Global optimization of omnidirectional wavelength selective emitters/absorbers based on dielectric-filled anti-reflection coated two-dimensional metallic photonic crystals.

We report the design of dielectric-filled anti-reflection coated (ARC) two-dimensional (2D) metallic photonic crystals (MPhCs) capable of omnidirectional, polarization insensitive, wavelength selective emission/absorption. Using non-linear global optimization methods, optimized hafnium oxide (HfO2)-filled ARC 2D Tantalum (Ta) PhC designs exhibiting up to 26% improvement in emittance/absorptance at wavelengths λ below a cutoff wavelength λc over the unfilled 2D TaPhCs are demonstrated. The optimized designs possess high hemispherically average emittance/absorptance εH of 0.

Enabling ideal selective solar absorption with 2D metallic dielectric photonic crystals.

A metallic dielectric photonic crystal with solar broadband, omni-directional, and tunable selective absorption with high temperature stable (1000 °C, 24 hrs) properties is fabricated on a 6" silicon wafer. The broadband absorption is due to a high density of optical cavity modes overlapped with an anti-reflection coating. Results allow for large-scale, low cost, and efficient solar-thermal energy conversion.

Analytic solution for N-electrode actuated piezoelectric disk with application to piezoelectric micromachined ultrasonic transducers.

In this work, the deflection equation of a piezoelectrically-driven micromachined ultrasonic transducer (PMUT) is analytically determined using a Green's function approach. With the Green's function solution technique, the deflection of a circular plate with an arbitrary circular/ring electrode geometry is explicitly solved for axisymmetric vibration modes. For a PMUT with one center electrode covering ≈60% of the plate radius, the Green's function solution compares well with existing piece-wise and energy-based solutions with errors of less than 1%.

Design of wide-angle selective absorbers/emitters with dielectric filled metallic photonic crystals for energy applications.

The design and simulation of a wide angle, spectrally selective absorber/emitter metallic photonic crystal (MPhC) is presented. By using dielectric filled cavities, the angular, spectrally selective absorption/emission of the MPhC is dramatically enhanced over an air filled design by minimizing diffraction losses. Theoretical analysis is performed and verified via rigorous coupled wave analysis (RCWA) based simulations.

An equivalent network representation of a clamped bimorph piezoelectric micromachined ultrasonic transducer with circular and annular electrodes using matrix manipulation techniques.

An electric circuit model for a clamped circular bimorph piezoelectric micromachined ultrasonic transducer (pMUT) was developed for the first time. The pMUT consisted of two piezoelectric layers sandwiched between three thin electrodes. The top and bottom electrodes were separated into central and annular electrodes by a small gap.

Optimizing the electrode size of circular bimorph plates with different boundary conditions for maximum deflection of piezoelectric micromachined ultrasonic transducers.

The effect of plate electrode area on the deflection of a symmetric circular bimorph piezoelectric micromachined ultrasonic transducer (pMUT) with clamped and simply supported boundary conditions was studied for the first time. Distinct plate displacement shape functions were defined for the regions underneath and outside the active electrodes. The plate shape functions were solved analytically using classic plate theory in conjunction with the external boundary conditions and the internal ones between the two regions in order to calculate the exact plate displacement under both external voltage stimulus and acoustic pressure.

Theoretical modeling and equivalent electric circuit of a bimorph piezoelectric micromachined ultrasonic transducer.

An electric circuit model for a circular bimorph piezoelectric micromachined ultrasonic transducer (PMUT) was developed for the first time. The model was made up of an electric mesh, which was coupled to a mechanical mesh via a transformer element. The bimorph PMUT consisted of two piezoelectric layers of the same material, having equal thicknesses, and sandwiched between three thin electrodes.

High-damping carbon nanotube hinged micromirrors.

New developments in digital mirror devices (DMDs) require suspension hinges with a good damping and high temperature stability. Carbon nanotubes (CNTs) offer these unique properties. Herein it is shown how CNT hinges can be integrated in micromirrors.

A nanoscanning platform for bio-engineering: an in-plane probe with switchable stiffness.

Scanning probe microscopy (SPM) has been one of the most important tools to image and, hopefully, to manipulate bio-structures at micro/nanoscales. However, the current out-of-plane cantilever design makes it very difficult to extend the spectrum of the current SPM technology to meet many new functionalities arising from bio-engineering applications. An in-plane scanning probe concept is developed to accommodate the new functional requirements.

Analog tunable gratings driven by thin-film piezoelectric microelectromechanical actuators.

We present a microfabricated grating whose period can be tuned in analog fashion to within a fraction of a nanometer. The tunable angular range is more than 400 microrad in the first diffracted order. The design concept consists of a diffractive grating defined onto a 400-nm membrane, with the membrane subsequently strained in the direction perpendicular to the grating grooves by thin-film piezoelectric actuation.