A simple approach to develop a paper-based biosensor for real-time uric acid detection.

The current work reports the development of an inexpensive real-time sensing module for uric acid detection on a simple, disposable paper substrate. Detection is based on a capacitive measurement system using functional ZnO hexagonal rods on pulse-electrodeposited Cu interdigitated electrodes (IDEs) over hydrophobic A4 paper. Both the prepared hydrophobic A4 paper and ZnO hexagonal rods are well characterized using field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), UV-visible spectrophotometry (UV-Vis), Raman spectroscopy, and contact angle measurement. Arduino IDE software is used to configure the Arduino Mega board to evaluate the change in the capacitance value and to display the corresponding uric acid concentration on a liquid crystal display (LCD) screen. The experimental result shows the linear relationship in the range of 0.1 mM-1 mM concentration of uric acid with a high sensitivity of 9.00 µF mM-1 cm-2 at 0.1 mM. The results indicate that the developed capacitance measurement unit can be employed for the early screening of uric acid in real samples for clinical applications. The reported proof-of-concept has huge potential towards the development of a disposable and inexpensive biosensor platform.

Multiplexed Gas Sensor: Fabrication Strategies, Recent Progress, and Challenges.

Due to miscellaneous toxic gases in the vicinity, there is a burgeoning need for advancement in the existing gas sensing technology not only for the survival of mankind but also for the industries based in various fields such as beverage, forestry, health care, environmental monitoring, agriculture, and military security. A gas sensor must be highly selective toward a specific gas in order to avoid incorrect signals while responding to nontarget gases. This may lead to complex scenarios depicting sensor defects, such as low selectivity and cross-sensitivity. Therefore, a multiplex gas sensor is required to address the problems of cross selectivity by combining different gas sensors, signal processing, and pattern recognition techniques along with the currently employed gas sensing technologies. The different sensing materials used in these sensor arrays will produce a unique response signal for developing a set of identifiers as the input that can be used to recognize a specific gas by its "fingerprint". This review provides a comprehensive review of chemiresistive-based multiplex gas sensors, including various fabrication strategies from expensive to low-cost techniques, advances in sensing materials, and a gist of various pattern recognition techniques used for both rigid and flexible gas sensor applications. Finally, the review assesses the current state-of-the-art in multiplex gas sensor technology and discusses various challenges for future research in this direction.