Manufacturing Technology Today

Sushil Kumar Singh ¹, Amita Gupta ¹

Affiliations
1 Solid State Physics Laboratory (SSPL), DRDO, Delhi, IN

Abstract

Piezoelectric thin films are an important family of functional materials in MEMS because they can provide electro- mechanical conversion directly and thus are useful for all kinds of motion sensors, actuators, transducers and acoustic devices. Most important factor for piezoelectric based MEMS devices is integration of functional piezoelectric layer onto the Si-substrate. Mainly we have two challenges, first is integration of piezoelectric functional films onto Si-substrate on wafer scale at low temperature and second is the patterning/ etching of the piezoelectric films with the resolution down to micrometer range. With an ever-expanding demand for data storage, transducers, actuators and MEMS systems applications, materials with superior ferroelectric and piezoelectric responses are of great interest. However, these film show high energy loss and low piezoelectric response compared with bulk materials, mainly due to the clamping effect of substrates and limited film thickness effect. One effective approach to resolving this problem is to fabricate nano domain thin films with a preferential crystallographic orientation that results in large piezoelectric deformation.

Highly textured nano-piezoelectric thin films were fabricated for MEMS application. The PZT films were characterized for micro-structural and electrical properties. We observed the piezoresponse in the range of 60 pm/V in PZT films. We propose to use these films for piezoelectric energy sourcing devices. It has been reported that common environmental vibrations such as those found in a building exhibit moderate amplitudes (<1g), and lower frequencies, typically between 60 Hz - 200 Hz, and fabrication of piezo thin film based micro-cantilevers vibrating at these frequencies might fulfill the requirements for a continuous power source of ~ 10 μW for a typical MEMS chip.

Keywords

MEMS, PZT Films, Nano-Fabrication, Micro-Structural and Electrical Properties.

Full Text

     

Kalpana Bhargava ¹, Thangamuthu Madasamy ², Sushil Kumar Singh ³, Murugesan Balamurugan ², Manickam Pandiaraj ², Niroj Kumar Sethy ¹, Chandran Karunakaran ²

Affiliations
1 Peptide and Proteomics Division, DIPAS, DRDO, Delhi, IN
2 Biomedical Research Laboratory, Department of Chemistry, VHNSN College, Virudhunagar, Tamil Nadu, IN
3 Solid State Physics Laboratory (SSPL), DRDO, Delhi, IN

Abstract

Determination of nitric oxide (NO), nitrite (NO₂ ^-) and nitrate (NO₃ ^-) is progressively becoming more important during hypoxia, nutrition and therapeutics. Hence, we have developed a novel electrochemical assay for the measurement of NO, NO₂ ^- and NO₃ ^- in volume miniaturized sample using cost effective screen printed microelectrode. It is based on the electrochemical oxidation and reduction reactions of NO and NO₂ ^- on the biosensor electrode immobilized with carbon nanotubes and copper, zinc superoxide dismutase (Cu,ZnSOD). The electrochemical characterization of Cu,ZnSOD (SOD1) immobilized microelectrode exhibited the characteristic quasi-reversible redox peak at the potential, +0.06 V vs. Ag/AgCl, confirming the immobilization of SOD1. Further, the carbon nanotubes modified electrode showed 2-fold increase in current response perhaps by enhancing the immobilization of SOD1 and also direct electron transfer between the deeply buried active site and the electrode surface. In order to measure these analytes selectively among the other co-existing biological substrates, nafion membrane for NO and cellulose acetate membrane for NO₂ ^- and NO₃ ^- were used. It showed a wide linear range of response over the concentration 100 nM to 1 mM for NO and 200 nM to 5 mM for NO₂ ^- with a detection limit of 50 nM NO₂ ^-. Moreover, it exhibited very higher sensitivity 96.4 nA μM^-1 for NO and 88.4 nA μM^-1 for NO₂ ^-. Using this microelectrode, the electrochemical assay kit for the determination of the NO₂ ^- and NO₃ ^- levels were estimated in human serum samples.

Keywords

Copper-Zinc Superoxide Dismutase, Electrochemical Assay Kit, Nitric Oxide, Nitrite, Nitrate.

Full Text