V. Seena

Indian Institute of Technology Bombay, Mumbai, Maharashtra, India

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Publications (13)9.18 Total impact

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    ABSTRACT: Th e evolution of today's sensors based on the micro/nano electromechanical systems (MEMS/NEMS) happened due to the revolutions in the well-established microelectronics technology. Th ough silicon is considered to be the primary material in microelectronics and hence in MEMS, many classes of MEMS devices have been realized using other potential materials like polymers. A class of MEMS sensors named nanomechanical cantilevers fi nd applications in the realization of many physical, chemical, and biological sensors. Improved sensitivity, reliability and also cost eff ectiveness of such sensor platforms have been achieved by the use of polymer materials, along with the employment of smart and compatible trans-duction techniques. Th is chapter summarizes our research work on development of polymer MEMS cantilever sensor platforms with four novel integrated electrical transduction mechanisms. In these techniques, the mechanical parameters of the polymer (SU-8) MEMS sensors can be translated into electrical output using (1) SU-8/CB nanocomposite (a piezoresistive approach), (2)integrated organic fi eld eff ect transistor of CantiFET (a strain sensitive transistor approach), (3) integrated Al doped ZnO TFT (a strain sensitive thin fi lm transistor approach) or (4) SU-8/ ZnO nanocomposite (a piezoelectric approach).
    Advanced Biomaterials and Biodevices, Edited by Ashutosh Tiwari and Anis N. Nordin, 07/2014: chapter 9: pages 305-342; Scrivener Publishing LLC, John Wiley & Sons, Inc., Hoboken, NJ, USA.., ISBN: 9781118774052
  • P. Ray, V. Seena, V.R. Rao
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    ABSTRACT: This work focusses on the development of a ZnO based piezo-resistive polymer cantilever sensor platform. Two different approaches have been taken, one based on Al-doped ZnO transistor (TFT) embedded in a polymeric micro-cantilever and another with a ZnO nanowire embedded microcantilever. Low Young's modulus of SU-8, low process temperature and high strain sensing capability of ZnO makes this platform an attractive option for sensor applications. For both the approaches, electromechanical and mechanical characterization results are reported in this work.
    Electron Devices and Solid-State Circuits (EDSSC), 2013 IEEE International Conference of; 01/2013
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    ABSTRACT: This letter reports a photoplastic (SU-8) piezoelectric (ZnO) nanocomposite route for realization of simple and low-cost piezoelectric microelectromechanical systems (MEMS). Integrating the ZnO nanoparticles into a photosensitive SU-8 polymer matrix not only retains the highly desired piezoelectric properties of ZnO but also combines the photopatternability and the optical transparency of the SU-8 polymer. These two aspects, therefore, lead to exciting MEMS applications with simple photolithography-based microfabrication. This approach opens up many new applications in the field of both sensor and energy harvesting.$\hfill$ [2011-0290]
    Journal of Microelectromechanical Systems 04/2012; 21(2):259-261. DOI:10.1109/JMEMS.2011.2178118 · 1.92 Impact Factor
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    ABSTRACT: Nanomechanical cantilever based biochemical sensors translate molecular interactions into nanomechanical motions that can be measured by different transduction techniques. Improved sensitivity, reliability, and also cost effectiveness of such sensor platforms have been achieved by the use of polymer materials, along with the employment of smart and compatible transduction techniques. This paper explores an ultrasensitive nanomechanical cantilever sensor platform with a novel transduction technique by integrating a strain-sensitive organic field-effect transistor within a polymer nanomechanical cantilever. This sensor, named as “organic CantiFET,” has a surface stress sensitivity of 401 $\hbox{ppm}\cdot[\hbox{mN/m}]^{-1}$ with a low-noise floor. This categorizes the organic CantiFET as an efficient biochemical sensor having a minimum detectable surface stress in the range of 0.18 mN/m.$\hfill$ [2011-0141]
    Journal of Microelectromechanical Systems 04/2012; 21(2):294-301. DOI:10.1109/JMEMS.2011.2175703 · 1.92 Impact Factor
  • International Journal of Nanoscience 08/2011; 10(04n05):739-. DOI:10.1142/S0219581X11008861
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    ABSTRACT: This paper reports an optimized and highly sensitive piezoresistive SU-8 nanocomposite microcantilever sensor and its application for detection of explosives in vapour phase. The optimization has been in improving its electrical, mechanical and transduction characteristics. We have achieved a better dispersion of carbon black (CB) in the SU-8/CB nanocomposite piezoresistor and arrived at an optimal range of 8-9 vol% CB concentration by performing a systematic mechanical and electrical characterization of polymer nanocomposites. Mechanical characterization of SU-8/CB nanocomposite thin films was performed using the nanoindentation technique with an appropriate substrate effect analysis. Piezoresistive microcantilevers having an optimum carbon black concentration were fabricated using a design aimed at surface stress measurements with reduced fabrication process complexity. The optimal range of 8-9 vol% CB concentration has resulted in an improved sensitivity, low device variability and low noise level. The resonant frequency and spring constant of the microcantilever were found to be 22 kHz and 0.4 N m(-1) respectively. The devices exhibited a surface stress sensitivity of 7.6 ppm (mN m(-1))(-1) and the noise characterization results support their suitability for biochemical sensing applications. This paper also reports the ability of the sensor in detecting TNT vapour concentration down to less than six parts per billion with a sensitivity of 1 mV/ppb.
    Nanotechnology 07/2011; 22(29):295501. DOI:10.1088/0957-4484/22/29/295501 · 3.67 Impact Factor
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    ABSTRACT: Organic sensors based on polymer microcantilevers and organic field effect transistors (OFETs) bring orthogonality to the sensing mechanism for different environmental and security applications. Orthogonolity is an important requirement from the point of reducing the false positives, which is of utmost importance for many applications. Development of polymer nanocomposite microcantilever based sensors for explosive vapour detection was reported. These polymer microcantilevers offer a deflection sensitivity of 1.1ppm for 1nm of deflection, which is the highest sensitivity reported till date. The sensor response to trinitrotoluene (TNT) vapours at a few parts per billion concentration levels was demonstrated. OFETs using poly 3-hexylthiophene (P3HT) and CuII tetraphenylporphyrin (CuTPP) composite as their active material were studied as sensors for detection of various nitro-based explosives. Significant changes were observed in the ON current (Ion) and transconductance (g(m)) of the OFET sensor after exposure to vapours of various explosive compounds. Sensor selectivity to explosive vapours over strong oxidizing agents was also demonstrated. Also, the change in conductivity for organic semiconducting material as a function of ionizing radiation was studied with an organic semiconducting material in resistor and OFET configurations. 30M Omega/Gy sensitivity for the organic resistor sensor and 28fA/Gy/1 mu m-width sensitivity for OFF current for the OFET sensor were observed. Moreover, changes in various other electrical parameters for an OFET sensor were also found proportional to the ionizing radiation dose.
    ECS Transactions 01/2011; 35(3):67-77. DOI:10.1149/1.3569900
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    ABSTRACT: This paper presents a micro cantilever based piezo-resistive sensor and its fabrication process along with two different techniques for signal conditioning of sensor output aimed for artificial nose applications. The proposed micro-cantilevers feature a special coating of 6-Marcaptonicotonic acid (6-MNA) on one side of the cantilever which leads to a selective reaction of the target analyte molecules with the functionalized cantilever surface. Two signal conditioning schemes, a novel current excitation method and a resistance to frequency conversion (RFC) method using a new proposed circuit are implemented to precisely read the piezo-resistance changes. Current excitation method is implemented using commercial ICs while RFC method is implemented using a low-power test chip constituting of instrumentation amplifier, buffer and comparator in 180nm mixed-mode CMOS technology. It is shown that the implemented RFC method provides a resolution of 5ppm and is useful for low-cost on-chip measurements involving the piezo-resistive sensors. Implemented current excitation method provides measurement resolution of 40 parts per billion with minimum SNR value of 5 dB which is better than previously-reported values.
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    ABSTRACT: In this paper, we report the development of a SU-8 based novel polymer composite microcantilever sensor designed for surface stress measurements. Nanoindentation study was carried out for measuring the Young's modulus of the polymer composite. A low cost process, optimized for fabrication of composite SU8 microcantilevers with thickness as small as 3 ¿m is developed and characterized as part of this work. Further, this paper also demonstrates the application of this polymer composite cantilever for explosive detection with the appropriate surface coatings carried out on the polymer surface.
    Micro Electro Mechanical Systems (MEMS), 2010 IEEE 23rd International Conference on; 02/2010
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    ABSTRACT: Micro fabricated sensors based on nanomechanical motion with piezoresistive electrical readout have become a promising biochemical sensing tool. The conventional microcantilever materials are mostly silicon-based. The sensitivity of the sensor depends on Young's modulus of the structural material, thickness of the cantilever as well as on the gauge factor of the piezoresistor. UV patternable polymers such as SU-8 have a very low Young's modulus compared to the silicon-based materials. Polymer cantilevers with a piezoresistive material having a large gauge factor and a lower Young's modulus are therefore highly suited for sensing applications. In this work, a spin coatable and photopatternable mixture of carbon black (CB) and SU-8, with proper dispersion characteristics, has been demonstrated as a piezoresistive thin film for polymer microcantilevers. Results on percolation experiments of SU-8/CB composite and fabrication of piezoresistive SU-8 microcantilevers using this composite are presented. With our controlled dispersion experiments, we could get a uniform piezoresistive thin film of thickness less than 1.2μm and resistivity of 2.7Ωcm using 10wt% of CB in SU-8. The overall thickness of the SU-8/composite/SU-8 is approximately 3μm. We further present results on the electromechanical characterization and biofunctionalization of the cantilever structures for biochemical sensing applications. These cantilevers show a deflection sensitivity of 0.55ppm/nm. Since the surface stress sensitivity is 4.1×10−3 [N/m]−1, these cantilevers can well be used for detection of protein markers for pathological applications.
    Solid State Sciences 09/2009; 11(9):1606-1611. DOI:10.1016/j.solidstatesciences.2009.06.009 · 1.68 Impact Factor
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    ABSTRACT: SU-8 cantilevers: Design, Fabrication and functionalization
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    ABSTRACT: Organic field effect transistors and polymer microcantilevers are two different classes of organic sensors with potential applications in biochemical sensing. Organic field effect transistors based on poly (3-hexylthiophene) and CuII tetraphenylporphyrin composite were investigated as sensors for detection of vapors of nitrobased explosive compounds. Significant changes, suitable for sensor response, were observed in transistor -on|| current (Ion) and conductance (S) after exposure. A similar device response was, however, not observed for oxidizing agents such as benzoquinone and benzophenone. Polymer microcantilevers offer a sensitive cost effective platform for explosive gas detection. These sensors with optical and electrical transduction mechanisms were designed and fabricated using SU-8 polymer and they are further functionalized with appropriate coating for explosive detection. Optical and electrical responses of respective microcantilevers to TNT vapors are also reported here.
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    ABSTRACT: Hydrogen Silsesquioxane (HSQ) has been recognized as a potential candidate as a low dielectric constant. Its dielectric, chemical and mechanical properties have been well studied in the literature. Apart from its advantage like low dielectric constant, it is easy to spin on any material and requires low temperature annealing. HSQ has been used as a sacrificial layer in surface micromachining of MEMS devices. However, the use of HSQ in biosensor applications has been limited by the fact that immobilization of biomolecules on HSQ surface has not been reported. Transformation of cage structure of HSQ into network structure terminated with OH bonds was achieved by annealing the HSQ layer in nitrogen ambient. Density of the surface siloxane bonds (Si-OH) per molecule was further increased by cleaving Si-H bonds using sulphochromic solution treatments. Thus obtained surface was functionalized for biological applications via grafting amine groups using aminosilanes (AEAPS). Surface modification using silanization process was investigated using contact angle measurement, Fourier Transform Infrared Spectroscopy (FTIR) and Atomic Force Microscopy (AFM). Following this, the surface was incubated with human immunoglobulin (HIgG). The efficacy and uniformity of immobilization of HIgG was proved by allowing FITC tagged goat anti-HIgG to react with the surface and observed under fluorescent microscope.
    Proceedings of European Material Research Society (EMRS) Spring Meeting, Congress Center, Strasbourg, France; 05/2007