Sensors

The rapid development of touch screens as well as photoelectric sensors has stimulated the fabrication of reliable, convenient, and human-friendly devices. Other than sensors that detect physical touch or are based on pressure sensing, proximity sensors offer controlled sensibility without physical contact. In this work we present a transparent and eco-friendly sensor made through layer-by-layer spraying of modified graphene oxide filled cellulose nanocrystals on lithographic patterns of interdigitated electrodes on polymer substrates, which help to realize the precise location of approaching objects. Stable and reproducible signals generated by keeping the finger in close proximity to the sensor can be controlled by humidity, temperature, and the distance and number of sprayed layers. The chemical modification and reduction of the graphene oxide/cellulose crystal composite and its excellent nanostructure enable the development of proximity sensors with faster response and higher sensitivity, the integration of which resolves nearly all of the technological issues imposed on optoelectronic sensing devices.   Zinc oxide (ZnO) nano-polycrystalline thin films has been prepared by cost-effective microwave assisted successive ionic layer adsorption and reaction (mSILAR) technique. ZnO/PANI prepared by in situ polymerization technique and thin films were fabricated using spin coating. X-ray Diffraction analysis confirms the presence of hexagonal wurtzite ZnO structure in the ZnO/PANI composite. The field emission scanning electron microscope revealed the porous nature of ZnO/PANI films with nanosized grains. We observed PANI intensively affected the structural and electrical properties of ZnO films. The examination of sensors was carried out in the liquefied petroleum gas (LPG) concentration range of 30 to 450 ppm. It was noticed that ZnO/PANI nanocomposite film possesses excellent LPG sensing properties at a room temperature compared with other volatile organic compounds, at an applied voltage of 1.5 V. The composite films also exhibited significant sensing response of ∼6.11 × 102 towards temperature and light with recovery and response time of ∼3.5 min and 2.16 min, respectively. Finally, the fabricated sensor showed good repeatability and sensitivity upon cyclic exposure to gas, light, and temperature. The ZnO/PANI nanocomposite film demonstrated overall sensing behavior in terms of sensor recovery time and response as well as repeatability. Simple, quick and novel method for the determination of diffusion properties through polymer films, based on Quantum Resistive Sensors made of Conductive Polymer nanoComposites is presented. The integral time lag method is employed for the calculation of diffusion coefficient, and the results are compared simultaneouslywith that of Fourier transform infrared spectroscopy and sorption method. Two model polymers, a semi-crystalline poly(lactic acid) and an amorphous poly(isobutylene-co-isoprene), are used to validate the study. A good correlation is established between the diffusion coefficient values derived from all techniques demonstrating the interest of such reliable, simple and cheap nanosensors for the quick determination (several minutes) of diffusion properties in polymer films. Our first results suggest that this technique is meaningful for the determination of barrier properties in nanocomposite membranes filled with platelets of graphene or clay. Biometrics is a promising technology for safeguarding the personal identity and digital information of every individual. This paper describes an easy-to-integrate and inexpensive method to improve the security of fingerprint scanners. An added layer of protection is proposed by integrating an anti-spoofing device that can be integrated to any commercial fingerprint scanners to enhance their security and prevent spoofing from prosthetic or dismembered fingers. The proposed device senses the capacitance and pulses from human fingers. We conducted over 300 tests on human and fake fingers. Our experimental results demonstrate that this novel device can identify the fake fingers with 100% accuracy. The device has a potential for being a cost-efficient and robust solution against spoofing.