The COVID-19 pandemic revealed a pressing need for the development of sensitive and low-cost point-of-care sensors for disease diagnosis. The current standard of care for COVID-19 is quantitative reverse transcriptase polymerase chain reaction (qRT-PCR). This method is sensitive, but takes time, effort, and requires specialized equipment and reagents to be performed correctly. This make it unsuitable for widespread, rapid testing and causes poor individual and policy decision-making. Rapid antigen tests (RATs) are a widely used alternative that provide results quickly but have low sensitivity and are prone to false negatives, particularly in cases with lower viral burden. Electrochemical sensors have shown much promise in filling this technology gap, and impedance spectroscopy specifically has exciting potential in rapid screening of COVID-19. Due to the data-rich nature of impedance measurements performed at different frequencies, this method lends itself to machine-leaning (ML) algorithms for further data processing. This review summarizes the current state of impedance spectroscopy-based point-of-care sensors for the detection of the SARS-CoV-2 virus. This article also suggests future directions to address the technology’s current limitations to move forward in this current pandemic and prepare for future outbreaks.

Acetaminophen is the most common cause of acute liver failure in the United States. The transfer of drugs to breast milk poses risks to infants, yet dosing guidelines are based on limited data from small studies. Currently, drug levels in milk are simply estimated through invasive blood draws. We present a new low-cost, textile-based electrochemical sensor for detecting acetaminophen at the point of use in breast milk. An embroidered conductive yarn (steel and silver) is used, which eliminates the need for complex microfabrication processes. A gold-nanoparticle-doped carbon ink-modified steel yarn serves as the working electrode, with pristine steel and silver yarns as counter and reference electrodes, respectively. Using square wave voltammetry, the sensor achieves a linear detection range of 9.9–166.4 μM in undiluted breast milk, with a limit of detection of 1.15 μM. This platform provides a simple and accessible alternative for drug monitoring

Succinylcholine (SUX) is a clinical anesthetic that induces temporary paralysis and is degraded by endogenous enzymes within the body. In high doses and without respiratory support, it results in rapid and untraceable death by asphyxiation. A potentiometric thread-based method was developed for the in-field and rapid detection of SUX for forensic use. We fabricated the first solid-contact SUX ion-selective electrodes from cotton yarn, a carbon black ink, and a polymeric ion-selective membrane. The electrodes could selectively measure SUX in a linear range of 1 mM to 4.3 $\mathsf{\mu }$M in urine, with a Nernstian slope of 27.6 mV/decade. Our compact and portable yarn-based SUX sensors achieved 94.1% recovery at low concentrations, demonstrating feasibility in real-world applications. While other challenges remain, the development of a thread-based ion-selective electrode for SUX detection shows that it is possible to detect this poison in urine and paves the way for other low-cost, rapid forensic diagnostic devices.