Design and analysis of novel micro displacement amplification mechanism actuated by chevron shaped thermal actuators

This paper presents design and analysis of microelectromechanical system (MEMS) based displacement amplification mechanism actuated using thermal actuators with enhanced performance. The proposed model consists of chevron shaped thermal actuators, an amplification mechanism capable of amplifying displacement 20 times and an electrostatic comb drives for sensing displacements. When voltage is applied to thermal chevrons, displacement is produced which is then amplified 20 times. Steady state static thermal electrical analysis is performed under variable resistivity and voltage bias of 2 V. In-plane reaction forces of magnitude 194.2 and 150.91 µN along X and Y-axis, respectively, thus producing displacement of 0.11 and 2.22 µm along X and Y-axis, respectively. Time domain simulations of device are carried with constant electrical resistivity, variable voltage and convective boundary conditions. Modal analysis of the mechanism is carried out to predict the natural frequencies and associated mode shapes of mechanism during free vibrations. The desired mode is at frequency of 286.160 kHz. Dynamic simulations including direct integration-transient, transient modal and steady state modal analysis are performed on the device for time span of 0.0006 s, under application of 25 g and frequency range of 200–300 kHz. Simulation results prove the viability of the mechanism as an amplification device with enhanced voltage–stroke ratio.

     

A Robust Wearable Point-of-Care CNT-Based Strain Sensor for Wirelessly Monitoring Throat-Related Illnesses

Point-of-care testing (POC) has the ability to detect chronic and infectious diseases early or at the time of occurrence and provide a state-of-the-art personalized healthcare system. Recently, wearable and flexible sensors have been employed to analyze sweat, glucose, blood, and human skin conditions. However, a flexible sensing system that allows for the real-time monitoring of throat-related illnesses, such as salivary parotid gland swelling caused by flu and mumps, is necessary. Here, for the first time, a wearable, highly flexible, and stretchable piezoresistive sensing patch based on carbon nanotubes (CNTs) is reported, which can record muscle expansion or relaxation in real-time, and thus act as a next-generation POC sensor. The patch offers an excellent gauge factor for in-plane stretching and spatial expansion with low hysteresis. The actual extent of muscle expansion is calculated and the gauge factor for applications entailing volumetric deformations is redefined. Additionally, a bluetooth-low-energy system that tracks muscle activity in real-time and transmits the output signals wirelessly to a smartphone app is utilized. Numerical calculations verify that the low stress and strain lead to excellent mechanical reliability and repeatability. Finally, a dummy muscle is inflated using a pneumatic-based actuator to demonstrate the application of the affixed wearable next-generation POC sensor.     

A Novel Hybrid Method for River Discharge Prediction

Accurate prediction of river discharge is essential for the planning and management of water resources. This study proposes a novel hybrid method named HD-SKA by integrating two decomposition techniques (termed as HD) with support vector regression (SVR), K-nearest neighbor (KNN) and ARIMA models (combined as SKA) respectively. Firstly, the proposed method utilizes local mean decomposition (LMD) to decompose the original river discharge series into sub-series. Next, ensemble empirical mode decomposition (EEMD) is employed to further decompose the LMD-based sub-series into intrinsic mode functions. Further, the EEMD decomposed components are used as inputs in three data-driven models to predict river discharge respectively. The prediction of all components is then aggregated to obtain the results of HD-SVR, HD-KNN and HD-ARIMA models. The final prediction is obtained by taking the average prediction of these models. The proposed method is illustrated using five rivers in Indus Basin System. In five case studies, six models were built to compare the performance of the proposed HD-SKA model. The data analysis results show that the HD-SKA model performs better than all other considered models. The Diebold-Mariano test confirms the superiority of the proposed HD-SKA model over ARIMA, SVR, KNN, EEMD-ARIMA, EEMD-KNN, and EEMD-SVR models.

     

Synthesis,characterization, and properties of new 3‐hexyl‐2,5‐diphenylthiophene: Phenylene vinylenes copolymers as colorimetric sensor for iodide anion

Four new conjugated copolymers P1 ‐ P4 have been prepared by the Horner‐Emmons and Knoevenagel polymerization reactions. P1 ‐ P4 were characterized by NMR, FTIR, cyclic voltammetry (CV), diffuse reflectance UV–vis spectroscopy (DR UV–vis), and thermal gravimetric analysis (TGA). The optical band gaps of these polymers, calculated from the onset absorption edge, were found between 2.15 and 2.34 eV. The band gaps calculated by CV were ranged between 1.94 and 2.57 eV. The presence of nitrile moiety on the phenylene vinylene unit is believed to influence the optical properties of these polymers, i.e., P3 and P4 have shown lower band gaps than P1 and P2 . All polymers possess good iodide anion sensing property over a wide range of other anions (F^?, Cl^?, Br^?, , CN^?), indicating their promise in fabricating selective iodide sensors. The initial colorless solution of polymers in THF changed to deep yellow upon the addition of aqueous solution of iodide salts along with significant changes in the UV–vis spectra of the polymers. The limit of detection (LOD) for P1‐P4 were found between 0.43 and 2.54 mM . These polymers constitute long alkoxy and alkyl side chains, bearing excellent solubility in most common organic solvents which warrants their suitability for photovoltaic devices application. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44948.     

Nanoscale jet collision and mixing dynamics

Micro- and macroscale investigations have shown that colliding drops always coalesce for small values of the Weber number We = rhoU2d/sigma. Our molecular dynamic simulations show that nanojets always recoil following head-on collision even though We --> 0. The duration between collision and recoil is a function of the nanojet impact velocity Uo and the nature of intermolecular interactions. Evaporation, which promotes mixing, occurs during recoil and is enhanced by reducing intermolecular interactions. Thereafter, mixing occurs through diffusion. The mixing dynamics are independent of Uo and the orifice shape. Consistent with a continuum analysis, the characteristic nanojet diameter at stagnation ds,1 proportional to Uo, recoil time following collision tau proportional to Uo-2, and the number of evaporating molecules N proportional to Uo.     

Tribological study of peroxide-cured EPDM rubber filled with electron beam irradiated PTFE powder

The aim of this work is the evaluation of the effects of electron beam modification of Polytetrafluoroethylene (PTFE) powder on the friction and wear properties of PTFE filled Ethylene-Propylene-Diene-Monomer (EPDM) rubber cured by a radical-initiated peroxide system. Friction and wear properties of EPDM vulcanizates were determined with the help of pin-on-disc tribometer in sliding contact with a steel-ball at room temperature without lubrication. PTFE powder was modified in atmospheric conditions with low (20 kGy) and high (500 kGy) irradiation doses using electron beam accelerator. The spectroscopic investigations reveal that the increasing concentration of reactive free radicals and functional groups with irradiation dose has a drastic influence on crosslinking efficiency due to their interference with peroxide radicals in curing process. As a result, non-irradiated and low-irradiated PTFE filled EPDM with higher crosslinking densities showed remarkably enhanced friction and wear properties. On the contrary, 500 kGy PTFE filled EPDM having significantly lower crosslinking density resulted in poor friction and wear characteristics. The apparent crosslinking density measured directly from the curing curves was found to be the most dominating parameter influencing friction, wear as well as the physical properties.     

Microstructure Characterization and Corrosion Resistance Behavior of New Cobalt-Free Maraging Steel Produced Through ESR Techniques

In this study, two different grades (M23 and M29) of cobalt-free low nickel maraging steel have been produced through electroslag remelting (ESR) process. The corrosion resistance of these ESR steels was investigated in 1 M H₂SO₄ solution using linear potentiodynamic polarization (LPP) and electrochemical impedance spectroscopy (EIS) techniques. The experiments were performed for different immersion time and solution temperature. To evaluate the corrosion resistance of the ESR steels, some significant characterization parameters from LPP and EIS curves were analyzed and compared with that of conventional C250 maraging steel. Irrespective of measurement techniques used, the results show that the corrosion resistance of the ESR steels was higher than the C250 steel. The microstructure of ESR steels was composed of uniform and well-distributed martensite accompanied with little amount of retained austenite in comparison with C250 steel.     

Effect of different softeners and sanforising treatment on pilling performance of polyester/viscose blended fabrics

An 80:20 polyester/viscose blended woven fabric was subjected to different softening and sanforising treatments. The effect of different softeners and sanforising treatments on the pilling propensity of the fabric was investigated. It was found that, while some types of softeners had no effect on pilling, the others may result in extreme deterioration of the pilling performance of polyester/viscose blended fabrics. It was further found that, in all cases, sanforising after softening adversely affects the fabric pilling performance.     

A deep tissue fluorescence imaging system with enhanced SHG detection capabilities

We describe a novel two‐photon fluorescence microscopy system capable of producing high‐quality second harmonic generation (SHG) images in thick turbid media by using an innovative detection system. This novel detection system is capable of detecting photons from a very large surface area. This system has proven effective in providing images of thick turbid samples, both biological and artificial. Due to its transmission detection geometry, the system is particularly suitable for detecting SHG signals, which are generally forward directed. In this article, we present comparative data acquired simultaneously on the same sample with the forward and epidetection schemes. Microsc. Res. Tech. 77:368–373, 2014. © 2014 Wiley Periodicals, Inc.     

Enhanced photoelectrochemical water splitting using zinc selenide/graphitic carbon nitride type-II heterojunction interface

The objective of this research is to construct a type-II heterojunction interface for effective photoelectrochemical (PEC) water splitting for hydrogen generation. A series of ZnSe/g-C₃N₄ heterojunctions is prepared by ultrasonication procedure and tested for PEC water splitting for the first time. The successful formation of ZnSe/g-C₃N₄ is confirmed by phase, morphological and optical analysis. Linear sweep voltammetry of 0.05 ZG (0.05% ZnSe/g-C₃N₄) showed a six-fold higher photocurrent density of 500 μA than g-C₃N₄. These results are supported by the Tafel slopes and PL (photoluminescence spectroscopy) studies by showing the smallest slope and lesser electron-hole recombination for 0.05 ZG. Increased lifetime of 107 ms and a higher donor density of 3.6 × 10¹⁹ cm^?3 for 0.05 ZG is observed. The smallest semicircle for 0.05 ZG in EIS implies the least charge transfer resistance among the prepared heterojunctions. All the results comply with each other showing the successful formation of type-II heterojunction for enhanced PEC water splitting.