Micro and Nano Systems Letters最新文献

Energy crisis and environmental pollution have been one of the major global issues. In this regard, the search for new energy storage materials is cheap, flexible and high-performance supercapacitors electrode which has become intensive. Also, reducing the amount of organic dyes polluting in water is a great significance. Herein, one-step electropolymerization of methylene blue on carbon fiber and the resulting films were applied to the supercapacitor. The high performance is associated to the outstanding conductivity, electrochemical stability and superior mechanical flexibility of carbon fiber. A new flexible electrode for supercapacitors was successfully fabricated by demonstrating with a good electrochemical performance and a promising alternative to reduce the water pollution.

The present research work reports on the fabrication of ultraviolet (UV) photodetectors using bismuth ferrite (BiFeO_3, BFO) thin films with varying thickness. Using the spray pyrolysis technique, BFO thin films were deposited on the glass substrate at 673?K. The deposited BFO thin films were characterized by Raman and FTIR spectroscopic analysis. The morphological analysis reveals uniform grain distribution for the prepared BFO samples. The optical analysis reveals that transmittance value decreases upon an increase in the thickness of BFO thin films and the calculated optical band gap value lies between 2.0 to 2.3?eV. The varying thickness of the BFO active layer was stacked between ITO and Al electrodes and the current–voltage (I–V) characteristics of the fabricated ITO/BFO/Al devices were studied under dark and UV illumination (λ?=?365?nm). It was observed that BFO with an optimum thickness (365?nm) exhibits higher photoresponsivity of 110?mA/W with an external quantum efficiency (EQE) of 37.30%. The impact of different thickness of the BFO active layer, the role of adsorption and desorption of oxygen (O₂) molecules upon the surface of BFO layers towards UV photoresponse characteristics were investigated.

Electronic skin (E-skin) capable of detecting various physical stimuli is required for monitoring external environments accurately. Here, we report an all-soft multiaxial force sensor based on liquid metal microchannel array for electronic skin applications. The proposed sensor is composed of stretchable elastomer and Galinstan, a eutectic gallium-indium alloy, providing a high mechanical flexibility and electro-mechanical durability. Liquid metal microchannel arrays are fabricated in multilayer and positioned along a dome structure to detect multi-directional forces, supported by numerical simulation results. By adjusting the height of the dome, we could control the response of the multiaxial sensor with respect to the deflection. As a demonstration of multiaxial force sensing, we were able to monitor the direction of multidirectional forces using a finger by the response of liquid metal microchannel arrays. This research could be applied to various fields including soft robotics, wearable devices, and smart prosthetics for artificial intelligent skin applications.

We propose a highly sensitive capacitive pressure sensor made of hollow polydimethylsiloxane (PDMS) foam with a three-dimensional network structure. The stiffness of the foam is adjusted by the viscosity of the PDMS solution. The fabricated PDMS-30 (PDMS 30 wt%) foam shows extremely high porosity (>?86%) approximately 19 times that of bare PDMS (PDMS 100 wt%) foam. Capacitive pressure sensors fabricated using the foam possess high sensitivity, good compressibility (up to 80% strain), and consistent output characteristics in a 2000-cycle test.

The extraordinary enhancement in heat transfer efficiency of nanofluids at extremely low volume fractions has attracted a lot of attention in identifying the governing mechanisms. The nanoscale effects, Brownian motion (random motion of particles inside the base fluid) and thermophoresis (diffusion of particles due to temperature gradient) are found to be important slip mechanisms in nanofluids. Based on these findings, a set of partial differential equations for conservation laws for nanofluids was formed. Since then, a large number of mathematical studies on convective heat transfer in nanofluids became feasible. The present paper summarizes the studies pertaining to instability of a horizontal nanofluid layer under the impact of various parameters such as rotation, magnetic field, Hall currents and LTNE effects in both porous and non-porous medium. Initially, investigations were made using the model considering fixed initial and boundary conditions on the layer, gradually the model was revised in the light of more practical boundary conditions and recently it has been modified to get new and more interesting results. The exhaustive analysis of instability problems is presented in the paper and prospects for future research are also identified.

This paper proposes a new design of bimorph-type electrothermal actuators based on flexible Ni-Co substrates and describes the results of the finite element method (FEM) simulation and performance evaluation of the actuators. In the design of the actuators, a multilayer structure consisting of an adhesion layer, two insulation layers, and a Pt (platinum) heater layer was formed on the Ni-Co flexible substrate that was patterned in an individual shape. The thin-film actuators proposed in this study could be detached from a Si carrier wafer and adhered to other micro or macrostructural elements. To investigate the temperature distribution and mechanical behavior of the actuators, multiphysics FEM simulations combining electrothermal and static structural analyses were carried out. The actuators were fabricated using conventional microfabrication and electroplating technologies on Si carrier wafer; then, the actuators were peeled off from the carrier wafer using the release process proposed in this paper. After fabricating the actuators, the deflection of their tips was evaluated and compared with that obtained from the FEM simulations.

We present a method to fabricate planar metal layers to be used as micromachined mirrors. Released mirrors of pure metal involve severe stress and reveal specific challenges to obtain planar mirror structures. Introducing sub-structures generating corrugated patterns, the metal mirror layers can be mechanically stabilized and undesired mirror bending can be reduced. For our investigations we used different arrangements of line structures on our metal mirrors, such as a group of straight or curved lines oriented differently. Comparing all the implemented different designs, planar micromirrors were achieved via sub-structures with a combination of straight lines arranged orthogonally to a single line. These planar micromirrors allow steering of the incident light by reflection and adjustment of the window transmittance. The presented low-cost method is suitable for large area fabrication of micromirror arrays, but also can be customized for other applications, where planar free-standing metal layers are required.

A comparative study of elastic properties and mode I fracture energy has been presented between conventional carbon fibre (CF)/epoxy and advanced carbon nanotube (CNT)/epoxy laminated composite materials. The volume fraction of CNT fibres has been considered as 15%, 30%, and 60% whereas; the volume fraction of CF has been kept constant at 60%. Three stacking sequences of the laminates viz.[0/0/0/0], [0/90/0/90] and [0/30/–30/90] have been considered in the present analysis. Periodic microstructure model has been used to calculate the elastic properties of the laminated composites. It has been observed analytically that the addition of only 15% CNT in epoxy will give almost the same value of longitudinal Young’s modulus as compared to the addition of 60% CF in epoxy. Finite element (FE) analysis of double cantilever beam specimens made from laminated composite has also been performed. It has been observed from FE analysis that the addition of 15% CNT in epoxy will also give almost the same value of mode I fracture energy as compared to the addition of 60% CF in epoxy. The value of mode I fracture energy for [0/0/0/0] laminated composite is two times higher than the other two types of laminated composites.

Preterm infants are prone to have higher risks of morbidity, disability and developmental delay compared to term infants. The primitive reflexes, inborn behaviors found in early life development, are shown to be a good tool to assess the integrity of the central nervous system of infants and to predict potential malfunctions. Among these reflexes, the non-nutritive sucking reflex plays an important role in indicating congenital abnormalities in brain development and feeding readiness, especially for premature infants. Conventionally, pediatricians evaluate the oral sucking power qualitatively based on their experiences, by using a gloved finger put inside the infant’s mouth. Thus, more quantitative solutions to assess the sucking power of preterm infants are necessary to support healthcare professionals in their evaluation procedures. Here, we developed a silver nanowire (AgNW)-based flexible pressure sensor to measure the non-nutritive sucking power of infants. The flexible sensor was fabricated using silver nanowires deposited on polydimethylsiloxane (PDMS) in a sandwich-like structure. The sensor based on the principle of strain gauge was attached to a ring-shaped connecting module, and then to a pacifier. The negative sucking pressure exerted by the infant deformed the sensor membrane, causing its electrical resistance to change without any contact between the infant’s mouth and the sensing element. The fabricated sensor was characterized and optimized to achieve both the suitable sensitivity and stability. Thanks to the excellent long-term electro-mechanical stability and high sensitivity, the developed sensor is expected to provide the means to quantitatively assess the non-nutritive sucking of infants, with a portable, low-cost, non-invasive and light-weight solution.