Research

The research is mainly concentrated to develop polymer nanocomposites applicable in various fields such as high performance Sensors, Actuators, Piezoelectrics, Dielectrics, Thermal Conductivity, FET, MEMS and lithographic patterning of materials. Both micro as well as nano fillers are used for polymer reinforcement and especially the effect of conductive fillers such as Graphene, CNT, Cellulose nanocrystal, Polyaniline, Conductive fillers etc. on polymer properties was investigated. I have extensive experience on graphene composite synthesis in the laboratory and fictionalized by chemical and thermal methods.  In short, I am interested to fabricate stronger, lighter and high performance multi functional materials which can have tremendous possibilities in technological field. My future interests are

  • Developments of high performance Biodegradable energy harvesting material, sensors, actuator, energy storage and other electronics applications.
  • Synthesis and chemical modification of eco-friendly polymers, nanomaterials and nanocomposites.

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.

Actuators

This Research work introduces an electroactive bionanocomposite based on poly(diethylene glycol adipate) (PDEGA) and cellulose nanocrystals (CNCs). The bionanocomposites were made using CNCs extracted from cotton and by optimizing its concentration in terms of the optical transmittance and viscosity. The characteristic properties of the materials were analyzed using contact angle measurements and Fourier transformation infrared spectra. Using the PDEGA/CNC bionanocomposite at a very low concentration of CNCs, a configurable lens having a robust, self-contained tunable optical structure was developed. The shape and curvature of the soft PDEGA/CNC device were controlled by applying voltage, and the focal length was measured. The simple structure, high optical transparency, biodegradability, thermal stability, high durability, and low power consumption make the new material particularly useful in fabricating a reconfigurable lens for future electronic and optical devices.

3D Printing electronics

3D printing method is one of the best techniques to control the pore size and porosity up to a desired range improving its sensing and energy storage behavior. The polymer composite filament has been developed from the extrusion process it is further molded for containing proper electrical conductivity properties. Further, 3D printing technology is applied to fabricate sensor and energy storage devices. The filaments obtained from the extruder is passed through the 3D printer and various types of designs are made. The porous sizes will be controlled by applying different designs to optimize the best properties of sensing and energy storage properties. Pore size and its distribution are two of the most important parameters to be considered for both sensor and energy storage performance.  This is the additional advantage of using 3D printing than the conventional die press method.

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