Microfluidic-based Split-Ring-Resonator Sensor for Real-time and Label-free Biosensing

AbstractIn this report, a split ring resonator (SRR), the most important building block of metamaterial, is fabricated and integrated with a microfluidic chamber for biosensing. The SRR is produced on a microwave printed circuit board while the microfluidic chamber is fabricated by casting of polydimethylsiloxane (PDMS). SRR was immobilized with Anti- Immunoglobulin G (IgG) for IgG detection by a standard covalent immobilization using Cystamine. The PDMS chamber was aligned and clamped on the circuit board and the electromagnetic response of the SRR sensor was continuously monitored when IgG analytes was flowed through the chamber. The reaction of Immunoglobulin G (IgG) and Anti-IgG results in a shift of resonance frequency. It was found that the response of the resonance frequency is sensitive to the IgG concentrations. Therefore, the SRR microfluidic scheme can be effectively used as an advanced bio-sensing device

Characterization of n-type and p-type semiconductor gas sensors based on NiOx doped TiO2 thin films

This work presents the development of n-type and p-type gas-sensitive materials from NiOx doped TiO2 thin films prepared by ion-assisted electron-beam evaporation. TiO2 gas-sensing layers have been deposited over a wide range of NiOx content (0-10 wt.%). The material analysis by atomic force microscopy, X-ray photoemission spectroscopy, and X-ray diffraction suggests that NiOx doping does not significantly affect surface morphology and Ni element may be a substitutional dopant of the TiO2 host material. Electrical characterization shows that NiOx content as high as 10% wt. is needed to invert the n-type conductivity of TiO2 into p-type conductivity. There are notable gas-sensing response differences between n-type and p-type NiOx doped TiO2 thin film. The responses toward all tested reducing gases tend to increase with operating temperature for the n-type TiO2 films while the response decreases with temperature for p-type TiO2 film. In addition, the p-type NiOx doping results in the significant response enhancement toward tested reducing gases such as acetone and ethanol at low operating temperature of 300 ºC

Metamaterial-inspired microfluidic-based sensor for chemical discrimination

This work proposes a metamaterial-inspired microfluidic-based chemical sensor. The sensor comprises a microwave split-ring resonator (SRR), an important building block of metamaterials, integrated with a disposable flow-channel made of a transparency film. The electromagnetic response of the sensor is observed in the presence of various analytes including glycerol, ethanol, and phosphate buffered saline. It is found that the resonance frequency in the transmission amplitude and the zero crossing in the reflection phase of the sensor are good features for discrimination of these analytes and for determining their concentrations. The developed metamaterial-inspired microfluidic-based chemical sensor has a potential for advanced chemical sensing applications.Kata Jaruwongrungsee, Withawat Withayachumnankul, Anurat Wisitsoraat, Derek Abbott, Christophe Fumeaux, and Adisorn Tuantranon

Dielectrophoretic spectra of translational velocity and critical frequency for a spheroid in traveling electric field

An analysis has been made of the dielectrophoretic (DEP) forces acting on a spheroidal particle in a traveling alternating electric field. The traveling field can be generated by application of alternating current signals to an octapair electrode array arranged in phase quadrature sequence. The frequency dependent force can be resolved into two orthogonal forces that are determined by the real and the imaginary parts of the Clausius–Mossotti factor. The former is determined by the gradient in the electric field and directs the particle either toward or away from the tip of the electrodes in the electrode array. The force determined by the imaginary component is in a direction along the track of the octapair interdigitated electrode array. The DEP forces are related to the dielectric properties of the particle. Experiments were conducted to determine the DEP forces in such an electrode arrangement using yeast cells (Saccharomyces cervisiate TISTR 5088) with media of various conductivities. Experimental data are presented for both viable and nonviable cells. The dielectric properties so obtained were similar to those previously reported in literature using other DEP techniques