Nano Bio Sensors

Gas Sensors

Correct estimation of air quality is very import as it can affect our lives directly or indirectly. CSIR-CEERI has developed Metal oxide based gas sensing platform for Ammonia (NH3), Carbon monoxide (CO), Hydrogen sulphide (H2S), Nitrogen dioxide (NO2), Ethanol (C2H5OH), and Propanol (C3H7OH) has been developed and demonstrated. Developed gas sensors can be integrated with electronics to make a portable as well as fixed kind of gas detection/ analysis system. Gas sensors are characterized in controlled environment chamber to observe response at various gas concentrations. Operating temperature for different gases is adjusted by the Platinum micro-heater. Platinum being a noble metal exhibits stable electrical properties and mechanical properties even at higher temperatures. Developed system has the capability to monitor data wirelessly (IoT enabled).

Micro-fluidic device

  • Fluid-FET: A highly sensitive ions flow controller, for lab-on-a-chip devices, operating through the nano channels and low external potentials is demonstrated. The ion concentration can be modulated up to 50% while working in sub-micro molar range. The device is a fluidic-field-effect transistor (Fluid-FET) which has nano dimensional fluidic channel, connecting two fluid reservoirs and is capped with high quality thermal SiO2 (i.e., low surface charges compared with plasma enhanced chemical vapor deposition SiO2), which is used as gate oxide; analogous to a channel between source–drain of a conventional FET.
  • Micro-Viscometer: Micro-Viscometer is realized using standard silicon process techniques such as thermally grown SiO2 is used as hydrophilic layer for passive pumping. Device is bonded using Anodic Bonding Technology. Developed micro-viscometer has the capability of measuring viscosity ranges from 0.1-10 Centipoise. Device needs less than 500 µL amount of sample for viscosity measurement and the response time is less than 5 minutes.
  • Particle separation: Particle Separation Chip provides size based separation of particles using physical filters. Numerous filters are used and the direction of flow is kept perpendicular to the flow direction in order to reduce channel clogging (cross flow filtration). Pillar type filters are used for separation of particles size greater than 6μm diameter. Another filter design Weir type filters are used for Plasma and particles below size of 2μm diameter. Polystyrene beads of sizes 5μm and 10μm have been separated. Almost all 10μm diameter beads get filtered out. The device is also used to separate blood cells from plasma in blood.

Chemical/Bio-chemical sensing platforms

  • Ion sensitive field effect transistor: CSIR-CEERI has developed Ion-Sensitive Field-Effect Transistor (ISFET) sensor as a pH sensing platform. ISFET devices have potential for the development of chemical/biochemical sensing platforms.
  • High electron mobility transistor (HEMT)
    • Femto level salt detection in water
    • Detection of Breast Cancer marker
    • Vbr> 100.0 V
  • CNT-FET based platform: CNTFET devices have been fabricated using shadow mask technology, which is clean process i.e. it avoids the use of chemicals and high temperature process, which is very unique in retaining and exploiting the intrinsic properties of pristine and functionalized materials. These devices are useful for highly sensitive and selective biological and gas sensors applications initially these devices have been tested for NO2 gas sensing.
  • Silicon nanowire platform: Poly-silicon nanowire platform for chemical/ bio-chemical sensing application has been developed using wet lateral reduction technique. Reduction process is reproducible with average lateral etch rate ~13nm/min @ 50°C. The process repeatability has been demonstrated by multiple experiments. Fabricated nanowires were integrated with metal lines and a gate electrode to make a nanowire FET device. Nanowire FET thus fabricated was characterized for drain current modulation by gate voltage. Nanowire FET device shows a significant sensitivity with gate voltage ie. 5 nAmp/ 10mV. Fabricated devices are under characterization for chemical/bio-chemical sensing.

Equipment Development

  • Shadow Mask Aligner: Silicon shadow mask with minimum 1 micron gap has been successfully fabricated to make stable and ohmic contacts with CNTs. A novel in-house shadow mask aligner has been designed, with a spatial alignment accuracy of ~ 1 µm. It also has provision to compensate the wedge error by using movements of three precision linear actuators, spotted under optical microscope