Martin Kocanda

Direct mass determination of hydrogen uptake using a quartz crystal microbalance

The authors demonstrate the application of a quartz crystal microbalance for direct mass determination of hydrogen uptake in storage materials in the pressure range of 0–40bars. The frequency shift of a quartz crystal coated with hydrogen absorbing materials is affected by the hydrogen mass uptake on the crystal, the pressure and the viscosity of the gases, and the crystal surface roughness, of which the roughness contribution has no analytical expression. Through a control experiment on the same crystal in helium, the roughness contribution in hydrogen can be derived and the frequency shift due to the hydrogen mass uptake can be obtained.

Detection of Cyclic Volatile Organic Compounds Using Single-Step Anodized Nanoporous Alumina Sensors

Conventional methods of fabricating anodic aluminum oxide (AAO) materials have utilized a multistep anodization process to manufacture sensor substrates and templates for nanostructured materials. The multistep anodization produces structured, highly ordered hexagonal nanopores. In this paper, it is demonstrated that a single-step anodization process employed in the manufacturing of moisture sensors produces a nanoporous AAO material suitable for the detection and discrimination of low molecular weight volatile organic compounds. Electrical impedance methods have been employed to analyze the electrical response of the single-step anodized AAO materials in the presence of cyclic organic vapors. The sensor exhibits an impedance response that discriminates cyclohexane, cyclohexene, benzene, toluene, and the three isomers of xylene. The impedance measurements have a direct correlation with the relative permittivity, polarizability, and dipole moments of the organic analytes.

Development of a DNA probe using barium strontium titanate

In this paper we report on the development of an electronic DNA sensor probe assembly using barium strontium titanate (BST) applied by pulsed laser deposition in conjunction with optical spectroscopy and impedance spectroscopy methods. To verify the binding of the probe to the BST, Fourier transform infrared (FTIR) spectroscopy and attenuated total reflectance (ATR) techniques were employed. FTIR and ATR were employed to verify the hybridization of the probe to an oligonucleotide target. In addition to the FTIR technique, direct capacitance and impedance spectroscopy measurements were used to verify the ability of the probe binding to the ceramic substrate and also the hybridization of the target DNA strand to the probe DNA strand. The proposed design has the advantages of label-free detection and large detectable capacitance changes upon hybridization, and does not require the application of a gold electrode layer.

DNA detection using a complementary metal-oxide semiconductor ring oscillator circuit

A DNA detection scheme has been implemented that utilizes a simple complementary metal-oxide semiconductor (CMOS) ring oscillator circuit. The detector oscillates at a fundamental frequency when using a nonhybridized single-strand DNA probe layer. Upon hybridization with a complimentary DNA strand, the oscillator output exhibits an increased frequency shift, indicating a genetic match. The probe assembly consists of a p-GaAs substrate containing a pulsed laser deposition-applied barium strontium titanate layer and an overlying sodium dodecyl sulfate lipid layer that serves to anchor a functionalized oligonucleotide probe. The oscillator circuit consisting of cascaded discrete complimentary n-channel and p-channel metal-oxide-semiconductor field-effect transistors was implemented using passive components arranged in a T-network to provide the associated fundamental time constant.

DNA sensing - an overview of present technology and future trends

This paper is an overview of the status of the present and future techniques used in DNA sensing. The fundamental concepts and principles of DNA chemistry are presented. Utilizing these concepts in DNA sensing are explained for the different techniques.

Enhanced hydrogen sensing employing electrodeposited palladium nanowires enclosed in anodized aluminum oxide nanopores

Palladium nanowire sensors have been limited to detecting small concentrations of molecular hydrogen (H2). Upon excessive hydrogen uptake, tunneling currents fuse the nanowires creating a short circuit causing permanent failure. Here we demonstrate that electrodeposited palladium nanowires enclosed within single-step anodized aluminum oxide nanopores reliably detect hydrogen concentrations greater than four percent and do not suffer the mechanical and electrical failures of conventional self-supporting nanowires. Multiple cycling of molecular hydrogen at 100% concentration and long-term exposure to high concentration of hydrogen does not contribute to permanent short-circuit failure of the sensor.

Design of a DNA probe using barium strontium titanate

A DNA probe assembly was developed using barium strontium titanate (BST) grown on a gallium arsenide (GaAs) substrate, using pulsed laser deposition (PLD). To verify the binding of probe material to BST, Fourier transform infrared spectroscopy and attenuated total reflectance (FTIR-ATR) techniques were used. The binding of the DNA probe strand was verified using capacitance measurement. Using this probe, the existence of the second strand can be sensed.

Detection and discrimination of alcohol vapours using single-step anodised nanoporous alumina sensors

The electrical response of single-step anodised alumina sensors to alcohol vapours containing one to four carbon atoms has been studied. In this investigation, the real and imaginary impedance components have been measured in response to the equilibrium saturation vapour pressure of methanol, ethanol, butanol and two structural isomers of propanol. The response to each type of alcohol produces characteristic impedance spectra that allow discrimination and possible recognition of each alcohol.

Time Domain Reflectometer for measuring liquid waste levels in a septic system

A Time Domain Reflectometer (TDR) level measurement device capable of generating and receiving electromagnetic waves for the measurement of waste water is presented. The primary objective is to measure the height of waste water in a tank and design an efficient measuring device. The TDR is based on the reflection mechanism, in which the time delay between the transmitted and reflected signals helps to determine the distance from the source to the surface of water, which is later used to calculate the height of water in the tank. The TDR is built using a 74AC14 IC, which is capable of producing pulse signals with very low rising and falling times that provide greater accuracy. Thus, the generated pulse signals are transmitted into the probe inserted in a tank. The total time taken by the pulse to travel the path to and from is calculated, which in return helps in calculating the height of the liquid in the tank. The functioning of the proposed TDR circuit and the biaxial probe is also tested in the laboratory.

Structural differentiation of common bacteria using impedance spectroscopy

Microbiological impedance spectroscopy has been employed for several decades to determine the presence and concentration of known bacteria and pathogens. Recent interest in lab-on-a-chip technology has been the motivation to develop miniature, accurate and rapid instrumentation to identify various strains of bacteria thus minimizing the necessity to culture, stain and perform population counting in a laboratory environment. In this work, a substrate using borosilicate microscope slides containing interdigitated electrodes was implemented to measure the real and imaginary impedance components of thin-film bacterial suspensions in the time domain. The resultant resistance and reactance changes that occur in real time appear to be characteristic of the cell wall composition that differentiates gram positive from gram negative bacteria.