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Highlights • An elementary precipitation method was used to synthesize ZnO QDs. • ZnO QDs guiding layer facilitate immobilization of uricase and showed high sensitivity, and reproducibility. • A three electrode based electrochemical biosensor was successfully fabricated for uric acid analysis. • Biosensor showed a wide linear range of detection 1–10 mM, covers the physiological range present in urine sample. Abstract Current trends in biosensors research include the application of nanomaterials to; provide a stable platform for immobilization and improving sensitivity. Quantum dots (QDs) are highly dispersed and extremely small (4–6 nm) particles that have been recognized to greatly increase the sensitivity by providing a larger surface area for binding of enzymes on the surface of the electrodes. Zinc oxide quantum dots (ZnO QDs) were synthesized through precipitation method and were characterized using TEM, UV–vis, and Raman spectroscopy to determine their properties. In this research work, we investigate the scope of ZnO QDs for the immobilization of uricase, an acidic enzyme having low isoelectric point, on the surface of nanostructured guiding layer for the detection of uric acid (UA). A three electrode based electrochemical biosensor was successfully fabricated using screen printing technique. The carbon electrode was modified with a thin film of ZnO QDs; the prepared thin film was utilized as working electrode. The ZnO QDs were subsequently functionalized with uricase to fabricate a selective uric acid sensor. The printed electrochemical sensor showed a linear response over a range of 1 mM–10 mM with a high sensitivity of 4.0 μA/mM cm−2. As a result, the procedures developed here are useful for the development of technologies accomplished of meeting the massive market demand of biosensors. [ABSTRACT FROM AUTHOR]

Polyethylene oxide (PEO) is a polymer hydrogel possessing ionic conductivity that varies with different percentage of absorbed water molecules and ions. This property makes it a good candidate to be used in humidity sensors’ active layers. The degree of crystallinity of PEO thin films decrease with increasing humidity that facilitates the ion conduction in the thin films, thus reducing the film impedance. In this research work, the humidity sensing properties of the thin films of semi-crystalline PEO have been investigated and the material is then modified to its amorphous dominant phase by heating the thin films beyond the melting point of the polymer. The slowly cooled resulting thin films had a waxy solid like appearance and showed an excellent response towards quantitative detection of relative humidity in the surrounding environment. The results show a roughly linear impedance versus relative humidity curve in the range of 0% RH to 90% RH with a very high maximum achieved sensitivity of ∼35 kΩ/%RH. The response and recovery times measured for the modified sensors were 2.8 s and 5.7 s respectively. The 30 day trial of stability readings showed a standard deviation of only 1%. The results prove thermally modified amorphous PEO thin films to be strong candidates for high end electronic relative humidity sensors. [ABSTRACT FROM AUTHOR]

• A piezocapacitive biodegradable pressure sensor has been fabricated. • Device targets low pressure measurements in tactile range of 0 < P < 5 kPa. • Nanofibrous PLGA-PCL membrane has been used as elastomeric dielectric. • It was used for wrist pulse monitoring and pressure mapping array applications. • 7 days of degradation caused a 19.5% decrease in sensitivity in low pressure range. High performance biodegradable electronic devices are becoming popular due to their enormous applications as biomedical implants or short term communication devices. They are biocompatible and eco-friendly. For example wearable or implantable biodegradable pressure sensors are very useful for cardiovascular or blood flow monitoring. But unfortunately very few previous researches have focused on developing biodegradable pressure sensors. Here we propose a composite of Polylactic-co-glycolic acid (PLGA) and Polycaprolactone (PCL) for biodegradable piezo-capacitive pressure sensor fabrication for low pressure measurement in tactile ranges of (0 < P < 5 kPa). An electrospun PLGA-PCL composite membrane has been used as elastomeric dielectric sandwiched between two biodegradable iron-zinc (Fe-Zn) bilayer electrodes, deposited on degradable Polyvinyl alcohol (PVA) substrate using electron beam deposition, and encapsulated in PLGA thin films for device fabrication. PLGA-PCL nanofibrous dielectric membrane is highly compressible and porous having tunable mechanical as well as dielectric properties and has been reported first ever for biodegradable pressure sensor application. The sensitivity of the sensor was found to be 0.863 ± 0.025 kPa−1 in the low pressure region (0 < P ≤ 1.86 kPa) which is quite high as compared to previous literature on biodegradable sensors so far while it adapted to a value of 0.062 ± 0.005 kPa−1 for high pressure region (1.86 kPa < P ≤ 4.6 kPa). The lowest detected value was 1.24 Pa (at 10mgf). Sensor showed good average response and recovery times of 251 ms and 170 ms respectively. In vitro degradation studies of the sensor were performed in PBS solution and sensor lost 60% of its initial weight during first two weeks of degradation and continued to degrade even after that. After one week of incubation sensor showed a 19.5% decrease in low pressure measurement range while there was no significant difference in upper detection range. It has been used to measure the arterial pulse wave on wrist and a 4 × 4 pressure sensor array was made to demonstrate its use in mapping different pressure points. [ABSTRACT FROM AUTHOR]