With the rise of zoonotic diseases in recent years, there is an urgent need for improved and more accessible screening and diagnostic methods to mitigate future outbreaks. The recent COVID-19 pandemic revealed an over-reliance on RT-PCR, a slow, costly and lab-based method for diagnostics. To better manage the pandemic, a high-throughput, rapid point-of-care device is needed for early detection and isolation of patients. Electrochemical biosensors offer a promising solution, as they can be used to perform on-site tests without the need for centralized labs, producing high-throughput and accurate measurements compared to rapid test kits. In this work, we detail important considerations for the use of electrochemical biosensors for the detection of respiratory viruses. Methods of enhancing signal outputs via amplification of the analyte, biorecognition of elements and modification of the transducer are also explained. The use of portable potentiostats and microfluidics chambers that create a miniature lab are also discussed in detail as an alternative to centralized laboratory settings. The state-of-the-art usage of portable potentiostats for detection of viruses is also elaborated and categorized according to detection technique: amperometry, voltammetry and electrochemical impedance spectroscopy. In terms of integration with microfluidics, RT-LAMP is identified as the preferred method for DNA amplification virus detection. RT-LAMP methods have shorter turnaround times compared to RT-PCR and do not require thermal cycling. Current applications of RT-LAMP for virus detection are also elaborated upon.

The tribology properties of TiO₂/POE, SiO₂/POE and TiO₂-SiO₂/POE nanolubricants were investigated for an automotive air-conditioning system with an electrically-driven compressor (EDC). A two-step preparation method was used in dispersing TiO₂ and SiO₂ nanoparticles into Polyol-ester (POE)-based lubricant at different volume concentrations of 0.01 to 0.1%. The coefficient of friction (COF) and wear scar diameter (WSD) were investigated using a Koehler four-ball tribo tester and microscopes. For the TiO₂/POE, SiO₂/POE and TiO₂-SiO₂/POE nanolubricants, respectively, the lowest COFs with maximum reduction were attained at 37.5%, 33.5% and 31.6% each at volume concentrations of 0.05%, 0.01% and 0.03%. The highest WSD reduction for the TiO₂/POE and SiO₂/POE mono nanolubricants were attained at 12.5% and 26.4%, respectively, at the same volume concentration of 0.01%. Meanwhile, the maximum reduction of WSD for the TiO₂-SiO₂/POE hybrid nanolubricant was reached at 12.4% at 0.03% volume concentration. As a conclusion, mono and hybrid nanolubricants with volume concentrations of less than 0.05% are suggested for use in air-conditioning systems with EDC because of their outstanding tribology performances. Further performance investigation of nanolubricants in the air-conditioning system is required to extend the present work.

This paper presents the design and analysis of MEMS piezoelectric energy harvester. Zinc oxide (ZnO) MEMS piezoelectric energy harvester has been utilized as piezoelectrically active cantilever for mechanical to electrical transduction. A COMSOL Multiphysics model was used which provide accurate information on the frequency, stress and voltage output of a ZnO piezoelectric energy harvester. Few design parameters have been studied which are rectangular cantilever, triangular cantilever, rectangular cantilever with proof mass and using different types of piezoelectric materials. The effects of varying geometrical dimensions of the device were also investigated. From simulation results, it was found out that ZnO piezoelectric energy harvester with the length of 150 μm, width 50 μm and thickness of 4 μm generates 9.9184 V electric potential under the resonance frequency of 0.71 MHz and 1 μN/m ² mechanical force applied.

This paper uses finite element method to obtain the optimal performance of piezoresistive microcantilever sensor by optimizing the geometrical dimension of both cantilever and piezoresistor. A 250 μm × 100 μm × 1 μm SiO2 cantilever integrated with 0.2 μm thick Si piezoresistor was used in this study. The sensor performance was measured on the basis of displacement sensitivity and surface stress sensitivity. The resulting maximum displacement value is about 0.7 nm for an applied load of 250 pN. A comparison between polySi and SiO2 cantilever has been carried out which shows the latter gives higher displacement for the same applied load. The sensor sensitivity was investigated by varying cantilever thickness as well as piezoresistor thickness. Simulation results show that the cantilever sensitivity is maximum when both the cantilever and the piezoresistor thicknesses are at minimum. Simulations were also conducted on the effects of incorporating various stress concentration region (SCR) designs at the bottom of the cantilevers. Cantilevers with incorporated stress concentration regions shows improved sensitivity over the cantilever without SCR. The cantilever with a rectangular shaped SCR extended up to the edge of the cantilever width yields a maximum Mises stress of 0.73 kPa compares to the other designs. For the same design, the cantilever with minimum SCR thickness of 0.2 μm yields maximum stress which results in maximum sensitivity.

Quartz Crystal Microbalance (QCM) is a device that allows non-destructive measurements of r in situ reaction activities. In this article, an array comprising of six 3MHz QCM sensors in an array were characterized using a vector network analyzer and OpenQCM, a portable measuring instrument that measures change in resonance frequency. Measurements of S21 transmission characteristics using the vector network analyzer provides the resonance frequency and can also be used to derive the RLC equivalent electrical circuit values of a resonant two-port network based on the Butterworth-Van Dyke model. In this work, Rm, Lm, Cm and Co were obtained via curve-fitting of the measurement results to the simulated results. Measurements were done in triplicates to verify reproducibility for all 6 sensors. For comparison, measurements were also done using a portable, open-source instrument, OpenQCM. The OpenQCM instrument directly measures changes in resonance frequencies, making it ideal for biosensing experiments, which correlate changes in mass with changes in resonance frequencies. Comparison between resonance frequency measurements using VNA and OpenQCM exhibit low percentage difference 0.2%. This QCM sensor array has the potential of conducting real-time, point-of-care analyses for detection of biological molecules.