Recent Submissions

  • Transparent biocompatible sensor patches for touch sensitive prosthetic limbs

    Nag, Anindya; Mukhopadhyay, Subhas; Kosel, Jürgen (Institute of Electrical and Electronics Engineers (IEEE), 2016-12-26)
    The paper presents the fabrication of transparent, flexible sensor patches developed using a casting technique with polydimethylsiloxane (PDMS) as substrate and a nanocomposite of carbon nanotubes (CNTs) and PDMS as interdigital electrodes. The electrodes act as strain sensitive capacitor. The prototypes were used as touch sensitive sensors attached to the limbs. Experiments results show the sensitivity of the patches towards tactile sensing. The results are very promising and can play a key role in the development of a cost efficient sensing system attached to prosthetic limbs.
  • Fabrication and characterization of magnetic composite membrane pressure sensor

    Khan, Mohammed Asadullah; Alfadhel, Ahmed; Kosel, Jürgen; Bakolka, M. (Institute of Electrical and Electronics Engineers (IEEE), 2016-04-20)
    This paper describes a magnetic field powered pressure sensor, which comprises a coil array and a magnetic composite membrane. The composite membrane is made by embedding a ribbon of the amorphous soft magnetic alloy Vitrovac®, in a 17 mm x 25 mm x 1.5 mm Polydimethylsiloxane (PDMS) layer. PDMS is chosen for its low Young's modulus and the amorphous alloy for its high permeability. The membrane is suspended 1.5 mm above a 17x19 array of microfabricated planar coils. The coils are fabricated by patterning a 620 nm thick gold layer. Each coil occupies an area of 36000 μm2 and consists of 14 turns. The sensor is tested by subjecting it to pressure and simultaneously exciting it by a 24 A/m, 100 kHz magnetic field. A pressure change from 0 kPa to 5.1 kPa, results in a 5400 ppm change in the voltage output.
  • Improved detection limits for phthalates by selective solid-phase micro-extraction

    Zia, Asif I.; Afsarimanesh, Nasrin; Xie, Li; Nag, Anindya; Al-Bahadly, I. H.; Yu, P. L.; Kosel, Jürgen (Institute of Electrical and Electronics Engineers (IEEE), 2016-03-30)
    Presented research reports on an improved method and enhanced limits of detection for phthalates; a hazardous additive used in the production of plastics by solid-phase micro-extraction (SPME) polymer in comparison to molecularly imprinted solid-phase extraction (MISPE) polymer. The polymers were functionalized on an interdigital capacitive sensor for selective binding of phthalate molecules from a complex mixture of chemicals. Both polymers owned predetermined selectivity by formation of valuable molecular recognition sites for Bis (2-ethylhexyl) phthalate (DEHP). Polymers were immobilized on planar electrochemical sensor fabricated on a single crystal silicon substrate with 500 nm sputtered gold electrodes fabricated using MEMS fabrication techniques. Impedance spectra were obtained using electrochemical impedance spectroscopy (EIS) to determine sample conductance for evaluation of phthalate concentration in the spiked sample solutions with various phthalate concentrations. Experimental results revealed that the ability of SPME polymer to adsorb target molecules on the sensing surface is better than that of MISPE polymer for phthalates in the sensing system. Testing the extracted samples using high performance liquid chromatography with photodiode array detectors validated the results.
  • Performance enhancement of electronic sensor through mask-less lithography

    Nag, Anindya; Zia, Asif I.; Mukhopadhyay, S. C.; Kosel, Jürgen (Institute of Electrical and Electronics Engineers (IEEE), 2016-03-30)
    The escalating applications of miniaturized sensors have led the microelectronics industry to stay abreast with the precise micro-fabrication technologies. The following article describes a new technique for the fabrication of miniaturized interdigitated capacitive sensors that own highly sensitive and real-time detections capabilities. In standard lithographic procedure, the sensors are fabricated applying different photoresist materials that give rise to the variable characteristic profile of the fabricated product. Single crystal p-doped Silicon wafer was used as a substrate material due to its advantageous properties over Germanium. Heidelberg system was used for the maskless lithographic patterning of the new interdigital sensors on a silicon substrate. The process was carried out in a clean room in the absence of ultraviolet light at a fixed temperature. The fabricated sensors were used for inflammable gas sensing application. Electrochemical Impedance Spectroscopy was applied to read the resistive and capacitive impedance measured by the sensor. The results proclaimed that the fabricated sensors own better performance in LPG detection as compared to its commercial counterparts.
  • Novel sensing approach for LPG leakage detection: Part II: Effects of particle size, composition and coating layer thickness

    Mukhopadhyay, Subhas; Nag, Anindya; Zia, Asif; Li, Xie; Kosel, Jürgen (Institute of Electrical and Electronics Engineers (IEEE), 2015-10-30)
    Prominent research has been going on to develop a low-cost, efficient gas sensing system. The paper presents a continuation of our earlier research work done to develop a new sensing approach for gas detection at ambient conditions. The work exhibits the optimization of the response time of the sensor by inhabiting characteristic changes like variation in the concentration of the dispersion medium, thickness of the coating and the size of the dispersed medium. Different concentrations of the dispersion medium in the coated suspension were tested to determine the optimal composition required to achieve the highest sensitivity of the tin oxide (SnO2) layer towards the tested gas. The control over adsorption and desorption of the gas molecules in the coated layer was achieved by investigating the particle size of the dispersed medium. The response time of the coated sensor was encouraging and owns a promising potential to the development of a more efficient gas sensing system.
  • Novel sensing approach for LPG leakage detection: Part I: Operating Mechanism and Preliminary Results

    Mukhopadhyay, Subhas; Nag, Anindya; Zia, Asif; Li, Xie; Kosel, Jürgen (Institute of Electrical and Electronics Engineers (IEEE), 2015-10-30)
    Gas sensing technology has been among the topical research work for quite some time. This paper showcases the research done on the detection mechanism of leakage of domestic cooking gas at ambient conditions. MEMS-based interdigital sensors were fabricated on oxidized single crystal silicon surfaces by maskless photolithography technique. The electrochemical impedance analysis of these sensors was done to detect liquefied petroleum gas (LPG) with and without coated particles of tin oxide (SnO2) in form of thin layer.A thin-film of SnO2 was spin-coated on the sensing surface of the interdigital sensor to induce selectivity to LPG that consists of a 60/40 mixture of propane and butane respectively. The paper reports a novel strategy for gas detection under ambient temperature and humidity conditions. The response time of the coated sensor was encouraging and own a promising potential to the development of a complete efficient gas sensing system.
  • Post annealing performance evaluation of printable interdigital capacitive sensors by principal component analysis

    Zia, Asif Iqbal; Mukhopadhyay, Subhas Chandra; Yu, Paklam; Al-Bahadly, Ibrahim H.; Gooneratne, Chinthaka Pasan; Kosel, Jürgen (Institute of Electrical and Electronics Engineers (IEEE), 2015-06)
    The surface roughness of thin-film gold electrodes induces instability in impedance spectroscopy measurements of capacitive interdigital printable sensors. Post-fabrication thermodynamic annealing was carried out at temperatures ranging from 30 °C to 210 °C in a vacuum oven and the variation in surface morphology of thin-film gold electrodes was observed by scanning electron microscopy. Impedance spectra obtained at different temperatures were translated into equivalent circuit models by applying complex nonlinear least square curve-fitting algorithm. Principal component analysis was applied to deduce the classification of the parameters affected due to the annealing process and to evaluate the performance stability using mathematical model. Physics of the thermodynamic annealing was discussed based on the surface activation energies. The post anneal testing of the sensors validated the achieved stability in impedance measurement. © 2001-2012 IEEE.
  • Magnetic microfluidic platform for biomedical applications using magnetic nanoparticles

    Stipsitz, Martin; Kokkinis, Georgios; Gooneratne, Chinthaka Pasan; Kosel, Jürgen; Cardoso, Susana; Cardoso, Filipe; Giouroudi, Ioanna (Trans Tech Publications, 2015-05)
    Microfluidic platforms are well-suited for biomedical analysis and usually consist of a set of units which guarantee the manipulation, detection and recognition of bioanalyte in a reliable and flexible manner. Additionally, the use of magnetic fields for perfoming the aforementioned tasks has been steadily gainining interest. This is due to the fact that magnetic fields can be well tuned and applied either externally or from a directly integrated solution in the diagnostic system. In combination with these applied magnetic fields, magnetic nanoparticles are used. In this paper, we present some of our most recent results in research towards a) microfluidic diagnostics using MR sensors and magnetic particles and b) single cell analysis using magnetic particles. We have successfully manipulated magnetically labeled bacteria and measured their response with integrated GMR sensors and we have also managed to separate magnetically labeled jurkat cells for single cell analysis. © 2015 Trans Tech Publications, Switzerland.
  • Rapid and molecular selective electrochemical sensing of phthalates in aqueous solution

    Zia, Asif I.; Mukhopadhyay, Subhas Chandra; Yu, Paklam; Al-Bahadly, Ibrahim H.; Gooneratne, Chinthaka Pasan; Kosel, Jürgen (Elsevier BV, 2015-05)
    Reported research work presents real time non-invasive detection of phthalates in spiked aqueous samples by employing electrochemical impedance spectroscopy (EIS) technique incorporating a novel interdigital capacitive sensor with multiple sensing thin film gold micro-electrodes fabricated on native silicon dioxide layer grown on semiconducting single crystal silicon wafer. The sensing surface was functionalized by a self-assembled monolayer of 3-aminopropyltrietoxysilane (APTES) with embedded molecular imprinted polymer (MIP) to introduce selectivity for the di(2-ethylhexyl) phthalate (DEHP) molecule. Various concentrations (1-100. ppm) of DEHP in deionized MilliQ water were tested using the functionalized sensing surface to capture the analyte. Frequency response analyzer (FRA) algorithm was used to obtain impedance spectra so as to determine sample conductance and capacitance for evaluation of phthalate concentration in the sample solution. Spectrum analysis algorithm interpreted the experimentally obtained impedance spectra by applying complex nonlinear least square (CNLS) curve fitting in order to obtain electrochemical equivalent circuit and corresponding circuit parameters describing the kinetics of the electrochemical cell. Principal component analysis was applied to deduce the effects of surface immobilized molecular imprinted polymer layer on the evaluated circuit parameters and its electrical response. The results obtained by the testing system were validated using commercially available high performance liquid chromatography diode array detector system.
  • Thin PZT-Based Ferroelectric Capacitors on Flexible Silicon for Nonvolatile Memory Applications

    Ghoneim, Mohamed T.; Zidan, Mohammed A.; Al-Nassar, Mohammed Y.; Hanna, Amir; Kosel, Jürgen; Salama, Khaled N.; Hussain, Muhammad Mustafa (Wiley-Blackwell, 2015-04-24)
    A flexible version of traditional thin lead zirconium titanate ((Pb1.1Zr0.48Ti0.52O3)-(PZT)) based ferroelectric random access memory (FeRAM) on silicon shows record performance in flexible arena. The thin PZT layer requires lower operational voltages to achieve coercive electric fields, reduces the sol-gel coating cycles required (i.e., more cost-effective), and, fabrication wise, is more suitable for further scaling of lateral dimensions to the nano-scale due to the larger feature size-to-depth aspect ratio (critical for ultra-high density non-volatile memory applications). Utilizing the inverse proportionality between substrate's thickness and its flexibility, traditional PZT based FeRAM on silicon is transformed through a transfer-less manufacturable process into a flexible form that matches organic electronics' flexibility while preserving the superior performance of silicon CMOS electronics. Each memory cell in a FeRAM array consists of two main elements; a select/access transistor, and a storage ferroelectric capacitor. Flexible transistors on silicon have already been reported. In this work, we focus on the storage ferroelectric capacitors, and report, for the first time, its performance after transformation into a flexible version, and assess its key memory parameters while bent at 0.5 cm minimum bending radius.
  • Electromagnetically powered electrolytic pump and thermo-responsive valve for drug delivery

    Yi, Ying; Zaher, Amir; Yassine, Omar; Buttner, Ulrich; Kosel, Jürgen; Foulds, Ian G. (Institute of Electrical & Electronics Engineers (IEEE), 2015-04)
    A novel drug delivery device is presented, implementing an electrolytic pump and a thermo-responsive valve. The device is remotely operated by an AC electromagnetic field (40.5∼58.5 mT, 450 kHz) that provides the power for the pump and the valve. It is suitable for long-term therapy applications, which use a solid drug in reservoir (SDR) approach and avoids unwanted drug diffusion. When the electromagnetic field is on, the electrolytic pump drives the drug towards the valve. The valve is made of a magnetic composite consisting of a smart hydrogel: Poly (N-Isopropylacrylamide) (PNIPAm) and iron powder. The heat generated in the iron powder via magnetic losses causes the PNIPAm to shrink, allowing the drug to flow past it. When the electromagnetic field is off, the PNIPAm swells, sealing the outlet. In the meantime, the bubbles generated by electrolysis recombine into water, causing a pressure reduction in the pumping chamber. This draws fresh fluid from outside the pump into the drug reservoir before the valve is fully sealed. The recombination can be accelerated by a platinum (Pt) coated catalytic reformer, allowing more fluid to flow back to the drug reservoir and dissolve the drug. By repeatedly turning on and off the magnetic field, the drug solution can be delivered cyclically. © 2015 IEEE.
  • Flexible magnetoimpedance sensor

    Li, Bodong; Kavaldzhiev, Mincho; Kosel, Jürgen (Elsevier BV, 2015-03)
    Flexible magnetoimpedance (MI) sensors fabricated using a NiFe/Cu/NiFe tri-layer on Kapton substrate have been studied. A customized flexible microstrip transmission line was employed to investigate the MI sensors's magnetic field and frequency responses and their dependence on the sensors's deflection. For the first time, the impedance characteristic is obtained through reflection coefficient analysis over a wide range of frequencies from 0.1 MHz to 3 GHz and for deflections ranging from zero curvature to a radius of 7.2 cm. The sensor element maintains a high MI ratio of up to 90% and magnetic sensitivity of up to 9.2%/Oe over different bending curvatures. The relationship between the curvature and material composition is discussed based on the magnetostriction effect and stress simulations. The sensor's large frequency range, simple fabrication process and high sensitivity provide a great potential for flexible electronics and wireless applications.
  • A surface acoustic wave passive and wireless sensor for magnetic fields, temperature, and humidity

    Li, Bodong; Yassine, Omar; Kosel, Jürgen (Institute of Electrical and Electronics Engineers (IEEE), 2015-01)
    In this paper, we report an integrated single-chip surface acoustic wave sensor with the capability of measuring magnetic field, temperature, and humidity. The sensor is fabricated using a thermally sensitive LiNbO3 substrate, a humidity sensitive hydrogel coating, and a magnetic field sensitive impedance load. The sensor response to individually and simultaneously changing magnetic field, temperature and humidity is characterized by connecting a network analyzer directly to the sensor. Analytical models for each measurand are derived and used to compensate noise due to cross sensitivities. The results show that all three measurands can be monitored in parallel with sensitivities of 75 ppm/°C, 0.13 dB/%R.H. (at 50%R.H.), 0.18 dB/Oe and resolutions of 0.1 °C, 0.4%R.H., 1 Oe for temperature, humidity and magnetic field, respectively. A passive wireless measurement is also conducted on a current line using, which shows the sensors capability to measure both temperature and current signals simultaneously.
  • Fabrication and properties of multiferroic nanocomposite films

    Al-Nassar, Mohammed Y.; Ivanov, Yurii P.; Kosel, Jürgen (Institute of Electrical and Electronics Engineers (IEEE), 2015-01)
    A new type of multiferroic polymer nanocomposite is presented, which exhibits excellent ferromagnetism and ferroelectricity simultaneously at room temperature. The multiferroic nanocomposite consists of a ferroelectric copolymer poly(vinylindene fluoride-trifluoroethylene) [P(VDF-TrFE)] and high aspect ratio ferromagnetic nickel (Ni) nanowires (NWs), which were grown inside anodic aluminum oxide membranes. The fabrication of nanocomposite films with Ni NWs embedded in P(VDF-TrFE) has been successfully carried out via a simple low-temperature spin-coating technique. Structural, ferromagnetic, and ferroelectric properties of the developed nanocomposite have been investigated. The remanent and saturation polarization as well as the coercive field of the ferroelectric phase are slightly affected by the incorporation of the NWs as well as the thickness of the films. While the former two decrease, the last increases by adding the NWs or increasing the thickness. The ferromagnetic properties of the nanocomposite films are found to be isotropic.
  • Crystallographically driven magnetic behaviour of arrays of monocrystalline Co nanowires

    Ivanov, Yurii P.; Trabada, Daniel G.; Chuvilin, Andrey L.; Kosel, Jürgen; Chubykalo-Fesenko, Oksana A.; Vázquez., Manuel M. (IOP Publishing, 2014-11-07)
    Cobalt nanowires, 40 nm in diameter and several micrometers long, have been grown by controlled electrodeposition into ordered anodic alumina templates. The hcp crystal symmetry is tuned by a suitable choice of the electrolyte pH (between 3.5 and 6.0) during growth. Systematic high resolution transmission electron microscopy imaging and analysis of the electron diffraction patterns reveals a dependence of crystal orientation from electrolyte pH. The tailored modification of the crystalline signature results in the reorientation of the magnetocrystalline anisotropy and increasing experimental coercivity and squareness with decreasing polar angle of the 'c' growth axis. Micromagnetic modeling of the demagnetization process and its angular dependence is in agreement with the experiment and allows us to establish the change in the character of the magnetization reversal: from quasi-curling to vortex domain wall propagation modes when the crystal 'c' axis tilts more than 75° in respect to the nanowire axis.
  • An efficient biosensor made of an electromagnetic trap and a magneto-resistive sensor

    Li, Fuquan; Kosel, Jürgen (Elsevier BV, 2014-09)
    Magneto-resistive biosensors have been found to be useful because of their high sensitivity, low cost, small size, and direct electrical output. They use super-paramagnetic beads to label a biological target and detect it via sensing the stray field. In this paper, we report a new setup for magnetic biosensors, replacing the conventional "sandwich" concept with an electromagnetic trap. We demonstrate the capability of the biosensor in the detection of E. coli. The trap is formed by a current-carrying microwire that attracts the magnetic beads into a sensing space on top of a tunnel magneto-resistive sensor. The sensor signal depends on the number of beads in the sensing space, which depends on the size of the beads. This enables the detection of biological targets, because such targets increase the volume of the beads. Experiments were carried out with a 6. μm wide microwire, which attracted the magnetic beads from a distance of 60. μm, when a current of 30. mA was applied. A sensing space of 30. μm in length and 6. μm in width was defined by the magnetic sensor. The results showed that individual E. coli bacterium inside the sensing space could be detected using super-paramagnetic beads that are 2.8. μm in diameter. The electromagnetic trap setup greatly simplifies the device and reduces the detection process to two steps: (i) mixing the bacteria with magnetic beads and (ii) applying the sample solution to the sensor for measurement, which can be accomplished within about 30. min with a sample volume in the μl range. This setup also ensures that the biosensor can be cleaned easily and re-used immediately. The presented setup is readily integrated on chips via standard microfabrication techniques. © 2014 Elsevier B.V.
  • Low pull-in voltage electrostatic MEMS switch using liquid dielectric

    Zidan, Mohammed A.; Kosel, Jürgen; Salama, Khaled N. (Institute of Electrical and Electronics Engineers (IEEE), 2014-08)
    In this paper, we present an electrostatic MEMS switch with liquids as dielectric to reduce the actuation voltage. The concept is verified by simulating a lateral dual gate switch, where the required pull-in voltage is reduced by more than 8 times after using water as a dielectric, to become as low as 5.36V. The proposed switch is simulated using COMSOL multiphysics using various liquid volumes to study their effect on the switching performance. Finally, we propose the usage of the lateral switch as a single switch XOR logic gate.
  • Optimized 425MHz passive wireless magnetic field sensor

    Li, Bodong; Kosel, Jürgen (Institute of Electrical and Electronics Engineers (IEEE), 2014-06)
    A passive, magnetic field sensor consisting of a 425 MHz surface acoustic wave device loaded with a giant magnetoimpedance element is developed. The GMI element with a multilayer structure composed of Ni80Fe 20/Cu/Ni80Fe20, is fabricated on a 128° Y-X cut LiNbO3 LiNbO3 substrate. The integrated sensor is characterized with a network analyzer through an S-parameter measurement. Upon the application of a magnetic field, a maximum magnitude change and phase shift of 7.8 dB and 27 degree, respectively, are observed. Within the linear region, the magnetic sensitivity is 1.6 dB/Oe and 5 deg/Oe. © 2014 IEEE.
  • Introducing molecular selectivity in rapid impedimetric sensing of phthalates

    Zia, Asif I.; Mukhopadhyay, Subhas Chandra; Al-Bahadly, Ibrahim H.; Yu, Paklam; Gooneratne, Chinthaka Pasan; Kosel, Jürgen (Institute of Electrical and Electronics Engineers (IEEE), 2014-05)
    This research article reports a real-time and non-invasive detection technique for phthalates in liquids by Electrochemical Impedance Spectroscopy (EIS), incorporating molecular imprinting technique to introduce selectivity for the phthalate molecule in the detection system. A functional polymer with Bis (2-ethylhexyl) phthalate (DEHP) template was immobilized on the sensing surface of the inter-digital (ID) capacitive sensor with sputtered gold sensing electrodes fabricated over a native layer of silicon dioxide on a single crystal silicon substrate. Various concentrations (10 to 200 ppm) of DEHP in deionized MilliQ water were exposed to the sensor surface functionalized with molecular imprinted polymer (MIP) in order to capture the analyte molecule, hence introducing molecular selectivity to the testing system. Impedance spectra were obtained using EIS in order to determine sample conductance for evaluation of phthalate concentration in the solution. Electrochemical Spectrum Analyzer algorithm was used to deduce equivalent circuit and equivalent component parameters from the experimentally obtained impedance spectra employing Randle's cell model curve fitting technique. Experimental results confirmed that the immobilization of the functional polymer on sensing surface introduces selectivity for phthalates in the sensing system. The results were validated by testing the samples using High Performance Liquid Chromatography (HPLC-DAD). © 2014 IEEE.
  • Magneto-mechanical trapping systems for biological target detection

    Li, Fuquan; Kodzius, Rimantas; Gooneratne, Chinthaka Pasan; Foulds, Ian G.; Kosel, Jürgen (Springer Science + Business Media, 2014-03-29)
    We demonstrate a magnetic microsystem capable of detecting nucleic acids via the size difference between bare magnetic beads and bead compounds. The bead compounds are formed through linking nonmagnetic beads and magnetic beads by the target nucleic acids. The system comprises a tunnel magneto-resistive (TMR) sensor, a trapping well, and a bead-concentrator. The TMR sensor detects the stray field of magnetic beads inside the trapping well, while the sensor output depends on the number of beads. The size of the bead compounds is larger than that of bare magnetic beads, and fewer magnetic beads are required to fill the trapping well. The bead-concentrator, in turn, is capable of filling the trap in a controlled fashion and so to shorten the assay time. The bead-concentrator includes conducting loops surrounding the trapping well and a conducting line underneath. The central conducting line serves to attract magnetic beads in the trapping well and provides a magnetic field to magnetize them so to make them detectable by the TMR sensor. This system excels by its simplicity in that the DNA is incubated with magnetic and nonmagnetic beads, and the solution is then applied to the chip and analyzed in a single step. In current experiments, a signal-to-noise ratio of 40.3 dB was obtained for a solution containing 20.8 nM of DNA. The sensitivity and applicability of this method can be controlled by the size or concentration of the nonmagnetic bead, or by the dimension of the trapping well.

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