Research on Electric Impedance Spectroscopy of Living Cell Suspensions by a Chip with Microelectrodes

A microfabricated electrical impedance spectroscopy (EIS) chip with microelectrodes was developed.The substrate and the electrodes of the chip were made of glass and gold,respectively.The experimental results demonstrated that the EIS-chip could distinguish different solutions (physiological saline,culture medium,living cell suspension etc.) by scanning from 10Hz to 45kHz.A 6-element circuit model was used for fitting the real part and the imaginary part admittance curves of the living cell suspension.An actual circuit was also built and tested to verify the 6-element circuit model proposed.The micro-EIS chip has several advantages including the use of small sample volumes,high resolution and ease of operation.It shows good application prospects in the areas of cellular electrophysioiogy,drug screening and bio-sensors etc.

Nanowire Fabrication in Porous Alumina Tempalets Produced by Employing Sulphuric, Oxalic and Phosphoric Acids

We report the growth of silver nanowires with varying diameters in porous anodic aluminum-oxide (AAO) membranes by using the electroless deposition approach. This objective is carried out in 2 phases. In Phase 1, AAO membranes on high purity aluminum foils are electrochemically grown by a double anodization procedure. Three different electrolytes, sulphuric acid (H2SO4), oxalic acid (H2C2O4) and phosphoric acid (H3PO4), are employed to produce membranes with varying pore diameters. Other parameters such as interpore distance, barrier layer thickness and membrane thickness are also explored. In addition, characterization to modify the pore diameter and open the barrier layer of free standing AAO templates has been carried out. In Phase 2, metallic silver nanowires are grown by electroless deposition inside pores with varying diameters in AAO membranes. AAO membranes immersed in aqueous silver nitrate solutions are thermally reduced, and the resulting silver nanowires are characterized by using a scanning electron microscope (SEM).

A carbon nanotube-based sensing element

A carbon nanotube-based(CNT) sensing element is presented, which consists of substrate, insulating layer, electrodes, carbon nanotube and measuring circuit. The sensing components are a single or array of CNTs, which are located on the two electrodes. The CNT-based sensing element is fabricated by CVD (chemical vapor deposition)-direct-growth on micro- electrodes. The sensing model and measurement method of electromechanical property are also presented. Finally, the voltage-current characteristics are measured, which show that the CNT-based sensing element has good electrical properties.

A tip-coupled, two-cantilever, non-resonant microsystem for direct measurement of liquid viscosity

We report a non-resonant piezoelectric microelectromechanical cantilever system for the measurement of liquid viscosity.The system consists of two PiezoMEMS cantilevers in-line,with their free ends facing each other.The system is immersed in the fluid under test for viscosity measurement.One of the cantilevers is actuated using the embedded piezoelectric thin film to oscillate at a pre-selected non-resonant frequency.The second cantilever,the passive one,starts to oscillate due to the fluid-mediated energy transfer.The relative response of the passive cantilever is used as the metric for the fluid's kinematic viscosity.The fabricated cantilevers are tested as viscosity sensors by carrying out experiments in fluids with different viscosities.The viscometer can measure viscosity at a single frequency of choice,and hence some important considerations for frequency selection are discussed.A discussion on the energy coupling between the active and the passive cantilevers is presented.The novel PiezoMEMS viscometer architecture proposed in this work will overcome several challenges faced by state-of-the-art resonance MEMS viscometers,by enabling faster and direct measurement,straightforward calibration,and the possibility of shear rate-dependent viscosity measurement.

Glassy carbon microelectrodes minimize induced voltages,mechanical vibrations,and artifacts in magnetic resonance imaging

The recent introduction of glassy carbon(GC)microstructures supported on flexible polymeric substrates has motivated the adoption of GC in a variety of implantable and wearable devices.Neural probes such as electrocorticography and penetrating shanks with GC microelectrode arrays used for neural signal recording and electrical stimulation are among the first beneficiaries of this technology.With the expected proliferation of these neural probes and potential clinical adoption,the magnetic resonance imaging(MRI)compatibility of GC microstructures needs to be established to help validate this potential in clinical settings.Here,we present GC microelectrodes and microstructures—fabricated through the carbon micro-electro-mechanical systems process and supported on flexible polymeric substrates—and carry out experimental measurements of induced vibrations,eddy currents,and artifacts.Through induced vibration,induced voltage,and MRI experiments and finite element modeling,we compared the performances of these GC microelectrodes against those of conventional thin-film platinum(Pt)microelectrodes and established that GC microelectrodes demonstrate superior magnetic resonance compatibility over standard metal thin-film microelectrodes.Specifically,we demonstrated that GC microelectrodes experienced no considerable vibration deflection amplitudes and minimal induced currents,while Pt microelectrodes had significantly larger currents.We also showed that because of their low magnetic susceptibility and lower conductivity,the GC microelectrodes caused almost no susceptibility shift artifacts and no eddy-current-induced artifacts compared to Pt microelectrodes.Taken together,the experimental,theoretical,and finite element modeling establish that GC microelectrodes exhibit significant MRI compatibility,hence demonstrating clear clinical advantages over current conventional thin-film materials,further opening avenues for wider adoption of GC microelectrodes in chronic clinical applications.

Cyclotriphosphazene Fibre Reinforced Poly(benzoxazine-co-ε-caprolactam) Nanocomposites for Flame Retardant Applications

Cyclophosphazene nanotube （PZT） incorporated poly（benzoxazine-co-g-caprolactam） （P（BZ-co-CPL）） nano- composites were developed for improving flame retardant properties. The effects of PZT on the flammability properties of P（BZ-co-CPL） matrix were evaluated through UL-94 flammability test and limiting oxygen index （LOI）. The UL-94 results of P（BZ-co-CPL）/PZT hybrid nanocomposites showed V-1 rating, whereas neat P（BZ-co-CPL） showed burning rating. The LOI values are increased from 25.4 to 31.4 for 1.5 wt% PZT incorporated P（BZ-co-CPL） nanocomposite systems. SEM was used to study the char morphology of P（BZ-co-CPL）/PZT after being exposed to UL-94 flammability test. Data from thermal studies indicate that the PZT incorporated P（BZ-co-CPL） systems possess better Tg and thermal degradation behavior when compared to the neat P（BZ-co-CPL）. The values of dielectric constant are decreased with increasing temperature. From the values, it is ascertained that the P（BZ-co-CPL）/PZT systems exhibit stable dielectric behavior with regard to variation in temperature. The TEM images ascertain the uniform dispersion of PZT in the P（BZ-co-CPL） matrix.