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We report an approach of wafer-scale addressable single-crystalline graphene (SCG) arrays growth by using pre-patterned seeds to control the nucleation. The growth mechanism and superb properties of SCG were studied. Large array of free-standing SCG devices were realized. Characterization of SCG as nano switches shows excellent performance with life time (>22 000 times) two orders longer than that of other graphene nano switches reported so far. This work not only shows the possibility of producing wafer-scale high quality SCG device arrays but also explores the superb performance of SCG as nano devices. [ABSTRACT FROM AUTHOR]

Growth of monolayer, bi-layer, and tri-layer single-crystalline graphene (SCG) using chemical vapor deposition method is reported. SCG's mechanical properties and single-crystalline nature were characterized and verified by atomic force microscope and Raman spectroscopy. Electro-mechanical switches based on mono- and bi-layer SCG were fabricated, and the superb properties of SCG enable the switches to operate at pull-in voltage as low as 1V, and high switching speed about 100 ns. These devices exhibit lifetime without a breakdown of over 5000 cycles, far more durable than any other graphene nanoelectromechanical system switches reported. [ABSTRACT FROM AUTHOR]

We report a conductometric nanoparticle biosensor array to address the significant variation of electrical property in nanomaterial biosensors due to the random network nature of nanoparticle thin-film. Indium oxide and silica nanoparticles (SNP) are assembled selectively on the multi-site channel area of the resistors using layer-by-layer self-assembly. To demonstrate enzymatic biosensing capability, glucose oxidase is immobilized on the SNP layer for glucose detection. The packaged sensor chip onto a ceramic pin grid array is tested using syringe pump driven feed and multi-channel I-V measurement system. It is successfully demonstrated that glucose is detected in many different sensing sites within a chip, leading to concentration dependent currents. The sensitivity has been found to be dependent on the channel length of the resistor, 4-12 nA/mM for channel lengths of 5-20 µm, while the apparent Michaelis-Menten constant is 20 mM. By using sensor array, analytical data could be obtained with a single step of sample solution feeding. This work sheds light on the applicability of the developed nanoparticle microsensor array to multi-analyte sensors, novel bioassay platforms, and sensing components in a lab-on-a-chip. [ABSTRACT FROM AUTHOR]

This paper presents a polymer-based micropump for liquid control or drug delivery. The dimension of the pump was 20 × 24 × 3 mm. A pair of O-ring SU-8 passive valves was fabricated by lift-off technique to control the fluid movement. Micropumps with dimple, bridge, and cantilever valves were studied. The PZT bimorph acted on the polymer membrane to periodically drive fluid. The maximum flow rate was 16.4 ml/min, and the back pressure was 1,525 mmHO at 150 V (Vp-p). In frequency sweeping experiments, two flow rate peaks and back pressure peaks were analyzed. Bidirectional flow rate was achieved by changing the valve seat from a one-size hole to a step hole. The maximum backward flow rate was 5.1 ml/min, and the driving frequency was about 355 Hz higher than the forward flow rate driving frequency. [ABSTRACT FROM AUTHOR]

A processable approach to fabricate suspended and aligned single-walled carbon nanotube (SWNT) beams and cantilevers is presented in this article. Suspended dense SWNT membranes were aligned and deposited by a controlled dielectrophoresis process. A gallium focused ion beam at 30 keV and 50 pA with an optimized dose bombarded the SWNT membranes to prepare them for suspended nanoscale beams and cantilevers. To demonstrate the application of this process to nanoelectromechanical systems (NEMS), an SWNT switch was realized with a pull-in voltage of ∼7.8 V. Accordingly, the fabrication process of SWNT beams and cantilevers is believed to be very promising for prototyping of many NEMS devices such as switches, resonators, and biosensors. [ABSTRACT FROM AUTHOR]

The authors report pH-dependent conductance behaviors of single-walled carbon nanotube (SWCNT) multilayer thin-film sensors. SWCNTs are functionalized with carboxylic groups, and layer-by-layer assembled alternatively with polycation, polydiallyldimethyammonium chloride on the microfabricated metal electrodes. Current-voltage (I-V) characteristics show that the conductance of SWCNT multilayer thin-film sensors decreases with increase of pH values. On the other hand, the multilayer resistors with polymethylmethacrylate (PMMA) as a passivation layer demonstrate the increasing conductance with pH, opposite to the case of the absence of PMMA layer. The conductance change in the absence of PMMA attributes to doping/undoping of holes as charge carriers by molecular protonation/deprotonation of p-type semiconducting SWCNTs. With PMMA layer, concentration gradient of hydrogen ions on the dielectric forms the gate bias voltage, which changes the conductance of underlying semiconducting SWCNT layer. Each pH-dependent behavior has versatile applications for chemical and biological detections. [ABSTRACT FROM AUTHOR]

This paper explores the development of active sound transmission control systems for windows that can achieve a significant reduction in window noise transmission. Two major challenges need to be addressed in order to make the development of such noise blocking windows feasible. These are the need for a distributed actuation system that is optically transparent and the unavailability of a real-time reference signal that can be used by the active control system to provide advance information on the noise affecting the window. To address the first challenge, a transparent thin-film actuator (speaker) is first developed for the control system, which consists of a piezoelectric poly (vinylidene fluoride) (PVDF) thin film coated with compliant carbon nanotube-based transparent conductors on both sides. The developed thin-film speaker shows excellent acoustic response over a broad- band frequency range, and has the advantages of being flexible, transparent, thin, and lightweight. To address the second challenge of providing a time-advanced reference signal from a moving noise source, a small microphone array distributed on the outside wall of the home is used. New noise source identification algorithms are employed, by which an appropriate microphone from the array can be chosen to provide a reference signal. Experimental results show that over 12 dB reduction in sound transmission is achieved globally in the case of broadband sound, which demonstrates the effectiveness of the control system in blocking sound transmission. [ABSTRACT FROM AUTHOR]

PZT thin films of various thickness were deposited on Pt(111)/Ti/SiO2/Si(100) substrates by the sol-gel method. A new method to control the crystallographic orientation of the PZT thin films by modifying the coating layers in one annealing cycle is presented in this paper. PZT films with (111) and (100) preferred orientation were obtained using the multi-coating-layer-annealed and the one-coating-layer-annealed sol-gel methods, respectively. The optimized baking and annealing temperatures at 200 and 600?°C were obtained by analyzing the phase transformation of the PZT precursor solution. The effect of film thickness on the microstructures, crystalline phases, and electrical properties of the PZT films was investigated. Compared to the multi-coating-layer-annealed method, the one-coating-layer-annealed method decreases the residual stress of the PZT films. The remanent polarization increases with the thickness of the PZT films. The remanent polarization (Pr) and coercive fields (Ec) of the one-coating-layer-annealed PZT films with 1.6 µm thickness are 25.7 µC cm?2and 59.2 kV cm?1, respectively. New microcantilevers with two PZT piezoelectric elements and three electric electrodes were designed. These structures can be applied to microsensors, microactuators, or versatile devices having both sensing and actuating functions. The cantilevers were successfully fabricated with wet and dry combined bulk micromachining technique. [ABSTRACT FROM AUTHOR]

Abstract  The power consumption of a surface acoustic wave (SAW) sensor system was investigated using ANSYS and PSPICE. Simulation results show that several design parameters of the surface acoustic wave sensor, such as the center distance between two interdigital transducers (IDT), the thickness of the piezoelectric substrate, the finger space of the IDT, etc., can greatly affect the power consumption of the whole system. The results of this study will be helpful to optimum design and fabricate the SAW sensor systems with very low-power consumption. [ABSTRACT FROM AUTHOR]

The paper presents the modeling of two types of piezoelectric microcantilevers, the two-layer and two-segment piezoelectric cantilevers, in which the two piezoelectric parts perform sensor and actuator functions, respectively. An analytic model is proposed to evaluate the sensing and actuating effects of multiporph microcantilevers formed of several layers or segments of piezoelectric materials. The analytical model is used to analyze the tip deflection of the cantilever and the piezoelectric charge generated on the sensor element as a function of the microcantilever geometry. The cantilevers of sensing and actuation are compared for the different working situations of the two-layer and two-segment cantilevers. The theoretical results can be used to optimize the design of the piezoelectric cantilever structures. [ABSTRACT FROM AUTHOR]

All-PMMA-based tunneling magnetic sensors were fabricated by hot embossing replication with silicon templates. The silicon templates had smooth surfaces, positive profiles, and pyramid-like pits with a high aspect ratio. With this fast (20 min), simple (one-step), and repeatable method, the all-PMMA tunneling sensor platform yielded sharp tunneling tips with 75 μm in baseline and 50 μm in depth. The sensors were assembled and fixed with measurement circuits, after their electrodes were patterned with modified photolithography and Co film was deposited with e-beam evaporation. A natural frequency response of 1.3 kHz was observed, and a tunneling barrier height of 0.713 eV was tested. Due to the quadratic relation between magnetic force and the field, the sensor field response (7.0×106 V/T2) was also quadratic. The noise voltage at 1 kHz is 0.2 mV, corresponding to a magnet field of 0.46×10-6 T. The bandwidth of this sensor is 18 kHz. This new type of sensor platform is promising for the next generation of microsensing applications. [ABSTRACT FROM PUBLISHER]

A modified sol-gel multiple coating and annealing process was developed to prepare lead zirconate titanate PbZr 0.5 Ti 0.5 O 3 (PZT) thin films with various thickness on Pt(111)/Ti/SiO 2 /Si(100) substrates. The PZT films with thickness 280, 560 and 810 nm underwent one, two and three annealing cycles, respectively, which consisted of 5 coating layers, 10 coating layers and 15 coating layers. Surface morphology and phase structure of the thin films were studied by SEM and XRD, respectively. The relationship between the thickness, namely different annealing cycles, and degree of texture was investigated. The dielectric constant increases with increasing film thickness. The dielectric constant and dielectric loss of PZT films as functions of applied field and frequency had also been examined and discussed. [ABSTRACT FROM AUTHOR]

The first PMMA-based membrane tunneling accelerometers were fabricated by hot embossing replication with silicon molds. The silicon molds were prepared by a combinative etching technique involving anisotropic bulk etching and modified plasma dry etching. The constructed molds hold both pyramid pits and positive profile sidewalls with smooth surfaces and steep angles, which were necessary for the hot embossing demolding. After electrodes patterned on embossed PMMA structures, the accelerometers, 8 mm × 8 mm × 1 mm, were packaged and assembled on a measurement circuit board. The exponential relationship between tip currents and applied deflection voltages presented a tunneling barrier height of 0.17 eV. The natural frequency of sensors was about 128 Hz. The bandwidth of the feedback system was 6.3 kHz. The sensitivity of voltage over acceleration was 20.6 V/g, and the resolution was 0.2485 μg/√Hz (g = 9.8 m/s² ). [ABSTRACT FROM AUTHOR]

A prototype design of an inexpensive polymer-based tunneling accelerometer is described in this paper. Instead of silicon, polymethyl methacrylate (PMMA) is used as the mechanical material. By using silicon molds fabricated by conventional lithography and wet-etching techniques in hot embossing, PMMA structures can be replicated within 20 min. The performance of the tunneling sensor can be estimated and improved based on mechanical-level analysis by ANSYS and system-level analysis by MATLAB. The nonlinear tunneling mechanism and electrostatic actuation are linearized using small-signal approximation. To enhance the stability and broaden the bandwidth of the tunneling accelerometer system, a feedback control system with one zero and two poles is designed. The dynamic range of the system is greatly enhanced. The bandwidth of the closed-loop system is approximately 15 kHz. [ABSTRACT FROM PUBLISHER]

Metal-oxide-semiconductor field-effect transistor (MOSFET) arrays are fabricated on a 4-in silicon water by the combination of conventional microelectronic processes and layer-by-layer nanofabrication. The active and insulating layers were self-assembled as organized multilayers of 15-nm diameter SiO2 and 45-nm diameter SiO2 nanoparticles, respectively. The source, drain, and gate electrodes are made of metal thin films. The threshold voltage is 3 V, on-off current ratio 104, and mobility 2.1 × 10-2 cm-2 cm² .s. This prototype leads to a new approach to fabricate low-cost MOSFETs and integrated circuits based on the layer-by-layer self-assembly of nanoparticles and charged macromolecules. [ABSTRACT FROM AUTHOR]

Polymer materials are attracting more and more attention for the applications to microeIectronic/optoelectronic devices due to their flexibility, lightweight, low cost, etc. In this paper, fabrication and characterization of a polymer junction field-effect transistor (JFET), using poly (3,4-ethylenedioxythiophene) poly (styrenesuifonate) (PEDT/IPSS) as the channel and poly (2,5-hexyloxy p-phenylene cyanovinylene) (CNPPV) as the gate layer, are reported. The all-polymer JFET was fabricated by the conventional ultraviolet (UV) lithography techniques. The fabricated device was measured and characterized electrically. In the meantime, the comparisons were lists between polymer JFET and analogous inorganic semiconductor counterparts. Its pinch-off voltage reaches 1 V that is in the applicable range, and the current is -13.8 μA at zero gate bias. It demonstrates that the device operates in a very similar fashion to its conventional counterparts. [ABSTRACT FROM AUTHOR]

The assembly of multilayer films of gelatin onto glass substrates using layer-by-layer and lift-off (LbL-LO) technology to modify the surface topography and chemistry properties of in vitro cell culture scaffolds is described. The ability to generate such nanoscale systems containing cell-adhesive materials on optically transparent substrates with microscale lateral dimensions, nanoscale vertical dimensions, molecular vertical precision, and flexibility in material selection has important implications for tissue engineering, drug discovery, and basic research in cell biology. Toward this goal, a systematic study on the electrostatic adsorption properties of fluorescein 5-isothiocyanate-gelatin B (FITC-gelatin) was completed. In addition, the integration of protein nanoassembly with microlithographic feature definition was used to pattern three-dimensional FITC-gelatin nanofilms on planar glass substrates. The experimental results indicate that FITC-gelatin is negatively charged at pH 9 and can be alternately assembled with a positively charged polyion, poly(diallyldimethylammonium chloride) (PDDA), to form multilayer films on solid templates with thickness of 5-10 nm per bilayer. Furthermore, images of protein/polymer nanocomposites indicate that LbL-LO is an efficient way to realize the designed substrates. These findings will benefit future research on cell culture and tissue engineering that require methods of generating protein patterns to fabricate novel in vitro cell culture systems. [ABSTRACT FROM PUBLISHER]

Presents a piezoelectric micromotor based on the structure of serial bending arms. Components of serial bending arms; Driving mechanism of the micromotor; Measurement of the rotational speed; Fabrication processes; Mechanism and structure.

A low-cost mechanical exfoliation method is presented to transfer graphite to graphene for free-standing beam arrays. Nickel film or photoresist is used to peel off and transfer patterned single-layer or multilayer graphene onto substrates with macroscopic continuity. Free-standing graphene beam arrays are fabricated on both silicon and polymer substrates. Their mechanical properties are studied by atomic force microscopy. Finally, a graphene based radio frequency switch is demonstrated, with its pull-in voltage and graphene-silicon junction investigated. [ABSTRACT FROM AUTHOR]

Applications of metal halide perovskite have been rapidly developing in recent years. However, very little research focusing on basic growth kinetics of perovskite films can be found in the literature. This paper discusses a hybrid physical-chemical deposition process of planar perovskite films. A 2-D ANSYS Fluent simulation is presented to calculate the heat and mass transfer during the deposition process. An optimized mass flow configuration with a flow resistance imposed by a porous screen is shown to give a uniform distribution of the methylammonium iodide vapor precursor and an even surface deposition rate of perovskite films. Both steady and transient calculations indicate that increasing operating temperature or vessel pressure within certain limits can boost the surface deposition rate of perovskite. Limitations on working pressure are presented for preventing reverse flow into the chamber and associated deterioration of deposition uniformity of the perovskite films. [ABSTRACT FROM AUTHOR]

The authors report the fabrication and characterization of high-mobility thin-film transistors (TFTs) using layer-by-layer (LBL) nano self-assembled single-walled carbon nanotubes (SWCNTs) as the semiconducting material and SiO2 nanoparticles as the gate dielectric material. The channel length and the effective thickness of the SWCNT semiconductor layer are 50 μm and 38 nm, respectively. The effective thickness of the SiO2 dielectric layer is 180 nm. The SWCNT TFT exhibits p-type semiconductor characteristics and operates in the accumulation mode, with a hole mobility (μp) of 168.5 cm2/V s, a normalized transconductance (gm/W) of 0.5 S/m, a threshold voltage (Vth) of -3 V, and an on/off current ratio (Ion/off) of 4.2. The combination technique with LBL nano self-assembly and microlithography provides a simple, low-temperature, and highly efficient approach to fabricate inexpensive TFT devices. [ABSTRACT FROM AUTHOR]

Reports on the fabrication of organic field-effect transistors through spin coating or ion etching. Deposit of the dielectric semiconductor layers; Influence of device performance by the polypyrrole electrode; Mobility of the bipolar transistor.

The ‘trapped rainbow’ mechanism of graded gratings has been demonstrated only as a type of groove reflection. In this study, we investigate the physical mechanism of the ‘trapped rainbow’ and demonstrate that a small step increase (~1/50λ) in the depth of a single obstructed groove can terminate the propagation of surface terahertz (THz) waves and reflect them back. A single obstructed groove can easily manipulate the properties of THz waves by changing the depth or the refractive index of the groove because the cutoff frequency is highly sensitive to the property of the groove. In addition, waves transmitted and reflected by a single groove can be controlled periodically over a period of a 1/2  −  λ increase in depth owing to the interference of surface spoof plasmonics and Fabry–Perot resonance. This is an easy means of controlling surface THz waves and fabricating more compact integrated optical devices such as THz branch waveguides, band pass filters, reflectors, and splitters. [ABSTRACT FROM AUTHOR]

The thickness of perovskite absorber layer is a critical parameter to determine a planar structured perovskite solar cell’s performance. By modifying the spin coating speed and PbI2/N,N-dimethylformamide (DMF) solution concentration, the thickness of perovskite absorber layer was optimized to obtain high-performance solar cells. Using a PbI2/DMF solution of 1.3 mol/L, maximum power conversion efficiency (PCE) of a perovskite solar cell is 15.5% with a perovskite film of 413 nm at 5000 rpm, and PCE of 14.3% was also obtained for a solar cell with a perovskite film of 182 nm thick. It is derived that higher concentration of PbI2/DMF will result in better perovskite solar cells. Additionally, these perovskite solar cells are highly uniform. In 14 sets of solar cells, standard deviations of 11 sets of solar cells were less than 0.50% and the smallest standard deviation was 0.25%, which demonstrates the reliability and effectiveness of hybrid physical chemical vapor deposition (HPCVD) method. [ABSTRACT FROM AUTHOR]

A micro catalytic methane sensor was proposed and fabricated on a bulk fused quartz substrate using a high resolution screen printing technique for the first time, with reduced power consumption and optimized sensitivity. The sensor was designed by the finite element method and quartz was chosen as the substrate material and alumina support with optimized dimensions. Fabrication of the sensor consisted of two MEMS processes, lift-off and high resolution screen printing, with the advantages of high yield and uniformity. When the sensor’s regional working temperature changes from 250 °C to 470 °C, its sensitivity increases, as well as the power consumption. The highest sensitivity can reach 1.52 mV/% CH4. A temperature of 300 °C was chosen as the optimized working temperature, and the sensor’s sensitivity, power consumption, nonlinearity and response time are 0.77 mV/% CH4, 415 mW, 2.6%, and 35 s, respectively. This simple, but highly uniform fabrication process and the reliable performance of this sensor may lead to wide applications for methane detection. [ABSTRACT FROM AUTHOR]

This paper presents a generic approach to characterize and analyze the adhesion energy between graphene and different materials using nanoindentation of an atomic force microscope (AFM), which is extremely essential and critical for variety of graphene based micro- and nano-devices. AFM was used to press a free-standing graphene beam down to a substrate. During the retraction, the adhesion force (named as the secondary pull-off force) was measured to analyze the adhesion energy between the graphene beam and the substrate. This approach is easy for manipulation and it can detect the adhesion energy after the device fabrication. According to our measurement, the graphene/SiO2, graphene/gold, and graphene/graphene adhesion energies per area are approximately 270 mJ/m², 255 mJ/m², and 307 mJ/m², respectively. This result was used to predict the performances and guide the design of graphene M/NEMS devices. [ABSTRACT FROM AUTHOR]

Rapid detection of foodborne pathogens is a key step in the control of food related diseases. Conventional methods for the detection of food pathogens, although typically sensitive, Often require multiple time-consuming steps such as extraction, isolation, enrichment, counting, etc., prior to measurement, resulting in testing times which can be days. There is a need to develop rapid and sensitive detection methods. This review is intended to provide food scientists and engineers an overview of current rapid detection methods, a close look at the nanoparticles especially magnetic nanoparticle-antibody conjugates based methods, and identification of knowledge gaps and future research needs. [ABSTRACT FROM AUTHOR]

For the first time, we used a hybrid physical-chemical vapor deposition (HPCVD) method to fabricate perovskite solar cells (PSCs) based on perovskite films with both organic cations and halogen anions. A high power conversion efficiency (PCE) of 18.1% was achieved based on a mixed perovskite film of MAxFA1-xPb (IyBr1-y)3 and the efficiency of the PSCs with MAPbI3 and MAxFA1-xPbI3 films were 14.5% and 16.4%, respectively. Perovskite material components and bandgaps were precisely tuned to achieve high photoelectric conversion performance. Three different types of perovskite films employed include MAPbI3, MAxFA1-xPbI3, and MAxFA1-xPb (IyBr1-y)3 (which are also designated as MAPbI3, MA0.89FA0.11PbI3, and MA0.54FA0.46Pb (I0.94Br0.06)3 with the respective bandgaps of 1.60 eV, 1.58 eV, and 1.61 eV. The experimental results demonstrate the ability to fabricate both organic cation and halogen anion mixed perovskite films by the HPCVD method and achieve easily adjustable bandgaps. In addition, the perovskite films fabricated by HPCVD have superior surface morphology, large crystal size, and low surface roughness. Eventually, this vapor-based method will have great potential in the fabrication of large-area and flexible PSCs to promote commercial application and industrialization of future PSCs. [ABSTRACT FROM AUTHOR]

This paper presents a two-dimensional (2D) transient numerical model for simulating the vapor deposition process for growing perovskite films. The diffusion process of methylammonium iodide (MAI) vapor through the processing chamber to react with the lead iodide (PbI2) substrate and grow the perovskite layer is analyzed with a diffusion coefficient that has been determined by measuring thicknesses of perovskite layers grown in a chemical vapor deposition (CVD) chamber. Innovations applied to the CVD chamber to improve the uniformity of layer thickness and offer control over the growth process are applied and computationally assessed. One is the addition of screens at various strategic locations in the chamber to improve flow uniformity. Another is changing the locations of MAI sublimation bowls and chamber outlet numbers and locations. The results show that adding screens makes the MAI vapor flow more uniform in the plenum while allowing a quicker purge of the N2 inert gas. This leads to a higher and more uniform growth rate of perovskite. The MAI vapor flow is influenced by the reaction plenum geometry, so the chamber is expected to allow good control of the process to achieve uniform surface deposition rate and controlled grain growth of the perovskite layer. [ABSTRACT FROM AUTHOR]

Coherent anti-Stokes Raman scattering (CARS) microscopy is an attractive technique for label-free biochemical-specific characterization of biological specimens. However, it has very low sensitivity in monitoring and imaging molecules present in extremely low concentrations or at fast speeds. To improve this sensitivity, especially for multiplex CARS, the intensity of the pump beam and broadband Stokes beam should be enhanced simultaneously. Therefore, the gold shell particle and gold surface are demonstrated to enhance the forward and backward CARS, respectively. Results show that a signal enhancement factor of ~25;000 can be achieved for the gold surface and an even higher enhancement factor can be achieved for the gold shell particles. Thus, we can obtain an enhanced CARS signal in a broad spectral range, which will substantially improve the detection sensitivity of hyperspectral CARS spectroscopy and imaging. [ABSTRACT FROM AUTHOR]