Highly Sensitive Interdigitated Capacitive Humidity Sensors Based on Sponge-Like Nanoporous PVDF/LiCl Composite for Real-Time Monitoring.

In this study, a sponge-like poly(vinylidene fluoride) (PVDF)/lithium chloride (LiCl) nanocomposite-entrenched interdigitated capacitive (IDC) sensor was developed for real-time humidity-sensing applications. Here, we demonstrated a sponge-like nanoporous structure ranging from 200 nm to 2 µm size holes, the PVDF/LiCl structure fabricated on an interdigitated capacitor (IDC) electrode functioning as a high-performance sensor because of the presence of ionized LiCl. The nanoporous PVDF/LiCl composite-based humidity sensor exhibited a high sensitivity of 12.6 nF/% relative humidity (RH), a linearity of 0.990, and a low hysteresis of 2.6% in the range of 25-95% RH. The composite film exhibited a response time of 17.7 s, a recovery time of 21 s, and an intensified increase of 8.02 nF/s (a decrease of 6.7 nF/s). The sensor designed demonstrates ultra-high sensing characteristics with 10 times higher sensitivity, i.e., 12.678.96 pF/%RH as compared to other polymer-based composite humidity sensors. Owing to the sensing performance and portability, the proposed nanoporous PVDF/LiCl composite-based IDC sensor is expected to be a promising platform for a wide range of humidity-sensing applications, including real-time breath monitoring and non-contact sensing.

Ultrasensitive probeless capacitive biosensor for amyloid beta (Aß1-42) detection in human plasma using interdigitated electrodes.

Progressive aggregation and protein misfolding are the initial fundamental indicators of neurodegenerative disorders such as Alzheimer's disease (AD). In this study, a highly sensitive and novel method to detect amyloid beta (Aß) biomarkers, which are a hallmark of AD, using an immunoassay platform-based interdigitated capacitive biosensor, has been explored. For several decades, aptamers have classified as a novel class of molecular recognition probes comprising single-stranded complementary DNA sequences that bind to their identified targets with high specificity and affinity by an in vitro technique called SELEX (systematic evolution of exponential and enrichment). Aptamers, often referred to as "chemical antibodies", possess several highly obvious features for clinical use. The proposed sensing bio-device was fabricated and glazed with oligomeric Aß (oAß) aptamer and anti-oAß antibody, functionalized onto a Pt/Ti-featured SiO2 substrate. Subsequently, analytical studies were conducted to confirm that the specificity, sensitivity, and selective detection of the oAß-based bioengineered surfaces facilitate a label-free approach. The bionic capacitive sensor achieved real-time detection within 5 s (faster response than ELISA) under the femto-molar range concentrations of oAß peptide in plasma using anti-oAß antibody and oAß aptamer with ultra-high affinity. Furthermore, the prepared capacitive biochip was selective against plasma-borne antigens and standby for 100 days at 4 °C. The developed biosensor is suitable for point-of-care (POC) diagnostic applications owing to its portability and scalability. Furthermore, the superior efficacy of oAß in identifying AD has huge potential for biomedical applications.

Ultrasensitive and Reusable Graphene Oxide-Modified Double-Interdigitated Capacitive (DIDC) Sensing Chip for Detecting SARS-CoV-2.

This research reveals the promising functionalization of graphene oxide (GrO)-glazed double-interdigitated capacitive (DIDC) biosensing platform to detect severe acute respiratory syndrome coronavirus (SARS-CoV-2) spike (S1) proteins with enhanced selectivity and rapid response. The DIDC bioactive surface consisting of Pt/Ti featured SiO2 substrate was fabricated using GrO/EDC-NHS/anti-SARS-CoV-2 antibodies (Abs) which is having layer-by-layer interface self-assembly chemistry method. This electroactive immune-sensing platform exhibits reproducibility and sensitivity with reference to the S1 protein of SARS-CoV-2. The outcomes of analytical studies confirm that GrO provided a desired engineered surface for Abs immobilization and amplified capacitance to achieve a wide detection range (1.0 mg/mL to 1.0 fg/mL), low limit of detection (1 fg/mL) within 3 s of response time, good linearity (18.56 nF/g), and a high sensitivity of 1.0 fg/mL. Importantly, the unique biochip was selective against blood-borne antigens and standby for 10 days at 5 °C. Our developed DIDC-based SARS-CoV-2 biosensor is suitable for point-of-care (POC) diagnostic applications due to portability and scaling-up ability. In addition, this sensing platform can be modified for the early diagnosis of severe viral infections using real samples.