Fabrication, calibration, and preliminary testing of microcantilever-based piezoresistive sensor for BioMEMS applications

Rapid and Sensitive Detection of Severe Acute Respiratory Syndrome Coronavirus 2 in Label-Free Manner Using Micromechanical Sensors

Coronavirus (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has been identified as a deadly pandemic. The genomic analysis of SARS-CoV-2 is performed using a reverse transcription-polymerase chain reaction (RT-PCR) technique for identifying viral ribonucleic acid (RNA) in infected patients. However, the RT-PCR diagnostic technique is manually laborious and expensive; therefore, it is not readily accessible in every laboratory. Methodological simplification is crucial to combat the ongoing pandemic by introducing quick, efficient, and affordable diagnostic methods. Here, we report how microcantilever sensors offer promising opportunities for rapid COVID-19 detection. Our first attempt was to capture the single-stranded complementary DNA of SARS-CoV-2 through DNA hybridization. Therefore, the microcantilever surface was immobilized with an oligonucleotide probe and detected using complementary target DNA hybridization by a shift in microcantilever resonance frequency. Our results show that microcantilever sensors can discriminate between complementary and noncomplementary target DNA on a micro to nanoscale. Additionally, the microcantilever sensors’ aptitude toward partial complementary DNA determines their potential to identify new variants of coronavirus. Therefore, microcantilever sensing could be a vital tool in the effort to extinguish the spreading COVID-19 pandemic.

Highly selective sensor for the detection of Hg2+ ions using homocysteine functionalised quartz crystal microbalance with cross-linked pyridinedicarboxylic acid

This study reports an insightful portable vector network analyser (VNA)-based measurement technique for quick and selective detection of Hg2+ ions in nanomolar (nM) range using homocysteine (HCys)-functionalised quartz-crystal-microbalance (QCM) with cross-linked-pyridinedicarboxylic acid (PDCA). The excessive exposure to mercury can cause damage to many human organs, such as the brain, lungs, stomach, and kidneys, etc. Hence, the authors have proposed a portable experimental platform capable of achieving the detection in 20-30 min with a limit of detection (LOD) 0.1 ppb (0.498 nM) and a better dynamic range (0.498 nM-6.74 mM), which perfectly describes its excellent performance over other reported techniques. The detection time for various laboratory-based techniques is generally 12-24 h. The proposed method used the benefits of thin-film, nanoparticles (NPs), and QCM-based technology to overcome the limitation of NPs-based technique and have LOD of 0.1 ppb (0.1 μg/l) for selective Hg2+ ions detection which is many times less than the World Health Organization limit of 6 μg/l. The main advantage of the proposed QCM-based platform is its portability, excellent repeatability, millilitre sample volume requirement, and easy process flow, which makes it suitable as an early warning system for selective detection of mercury ions without any costly measuring instruments.

Ultrasensitive detection of cadmium ions using a microcantilever-based piezoresistive sensor for groundwater

This paper proposes the selective and ultrasensitive detection of Cd(II) ions using a cysteamine-functionalized microcantilever-based sensor with cross-linked ᴅʟ-glyceraldehyde (DL-GC). The detection time for various laboratory-based techniques is generally 12-24 hours. The experiments were performed to create self-assembled monolayers (SAMs) of cysteamine cross-linked with ᴅʟ-glyceraldehyde on the microcantilever surface to selectively capture the targeted Cd(II). The proposed portable microfluidic platform is able to achieve the detection in 20-23 min with a limit of detection (LOD) of 0.56 ng (2.78 pM), which perfectly describes its excellent performance over other reported techniques. Many researchers used nanoparticle-based sensors for the detection of heavy metal ions, but daily increasing usage and commercialization of nanoparticles are rapidly expanding their deleterious effect on human health and the environment. The proposed technique uses a blend of thin-film and microcantilever (micro-electromechanical systems) technology, which mitigate the disadvantages of the nanoparticle approaches, for the selective detection of Cd(II) with a LOD below the WHO limit of 3 μg/L.