Recent developments in minimally and truly non-invasive blood glucose monitoring techniques

The aim of this paper is to introduce the recent research and commercial developments in minimally and non invasive blood glucose monitoring technique

Dual feeding cavity resonator for efficiency enhancement in liquid heating applications

A new type of microwave resonator feeding topology is proposed to enhance the power delivered to a lossy sample for microwave heating applications. The method uses two input signals with equal phase and magnitude, instead of the usual one input. As a result, for the same total input power, the delivered power can be increased to twice the power than the case of the one input. A 2.45 GHz TM010 cylindrical cavity with dual input ports is used to heat a water sample with a total input power of 0.25 W. The efficacy of the proposed heating topology was verified by 3D electromagnetic simulation and heating measurements, including S-parameters, incident and reflected power, and thermal images. All measurement results support the increase in heating efficiency in the two port case, while using the same total amount of power as for the one port cas

Harmonics terminated L-band frequency quadrupler using composite right/left-handed transmission line

A design method for an L-band frequency quadrupler with composite right/left-handed transmission line is proposed. The left-handed transmission line in the proposed frequency quadrupler suppresses the fundamental component (f 0), while the composite right/left-handed lambda/4 open stub reduces unwanted higher-order harmonics. From the experimental results, unwanted harmonics are suppressed to achieve harmonic distortion of 51lambdadBc minimum with output phase noise of lambda94.34lambdadBc/Hz at 10lambdakHz offset

Microwave group delay time adjuster using parallel resonator

This letter describes the design of a group delay time adjuster (GDTA) using a parallel resonator. The GDTA consists of a variable capacitor and a variable equivalent inductor. These components are controlled by two bias voltages separately. The variable equivalent inductor is realized using a high impedance transmission line terminated with the variable capacitor. Group delay time can be adjusted by varying the capacitance and the inductance while keeping the fixed resonance frequency. When the proposed GDTA is fabricated on the Korean RFID frequency band (908.5-914MHz), we could obtain about 3ns group delay time variation with excellent flatnes

Novel variable coupling technique for microwave liquid heating and sensing

A simple new variable coupling technique is presented in this paper. The aim of the design is to optimize the coupling between the source and the microwave resonator in which the resonator can be used either as a microwave applicator or sensor. This technique suggests terminating the loop coupling between the coaxial transmission line and the cylindrical cavity with a variable capacitor. To prove the validity, the proposed approach was applied to a 2.45 GHz TM 010 cylindrical cavity for heating and sensing of several types of solvents. The experimental results show the capability to reach any coupling value when the resonator is loaded with various liquid samples by adjusting the value of the terminating capacitor

A new design of Doherty amplifiers using defected ground structure

In this letter, a new Doherty power amplifier having the ideal harmonic termination condition that has been usually ignored is proposed. A defected ground structure (DGS) is adopted on the ground pattern of the output lambda/4 impedance inverter of the carrier amplifier and output offset transmission line of the peaking amplifier that are essential for proper load modulation operation of a conventional Doherty amplifier. As a result of the second and third harmonic termination, excellent improvement in power added efficiency (PAE), gain, maximum output power as well as linearity is obtained. The acquired improvements in gain, maximum output power (P1 dB), PAE, and adjacent channel leakage ratio to wideband code division multiple access 2FA signal are 0.33 dB, 0.42 dB, 12.7%, and 5.1 dB, respectively. Moreover, physical length of microstrip line is shortened fairly by DGS, therefore the whole amplifier circuit size is considerably reduce

Microwave-enhanced antibacterial activity of polydopamine–silver hybrid nanoparticles

The ever-increasing risks posed by antibiotic-resistant bacteria have stimulated considerable interest in the development of novel antimicrobial strategies, including the use of nanomaterials that can be activated on demand and result in irreversible damage to pathogens. Microwave electric field-assisted bactericidal effects on representative Gram-negative and Gram-positive bacterial strains were achieved in the presence of hybrid polydopamine–silver nanoparticles (PDA–Ag NPs) under low-power microwave irradiation using a resonant cavity (1.3 W, 2.45 GHz). A 3-log reduction in the viability of bacterial populations was observed within 30 minutes which was attributed to the attachment of PDA–Ag NPs and associated membrane disruption in conjunction with the production of intra-bacterial reactive oxygen species (ROS). A synergistic effect between PDA and Ag has been demonstrated whereby PDA acts both as an Ag NP carrier and a microwave enhancer. These properties together with the remarkable adhesivity of PDA are opening a route to design of antibacterial adhesives and surface coatings for prevention of biofilm formation

Microwave Noninvasive Blood Glucose Monitoring Sensor: Penetration Depth and Sensitivity Analysis

Previously reported clinical performances of microwave noninvasive blood glucose monitoring sensor look promising. It is clear that dielectric properties are changing when the food intake takes place, but the exact physiological mechanism is not clear. In an attempt to figure out the physiological mechanism of microwave noninvasive blood glucose monitoring sensor, this paper presents a series of studies to find out a) the penetration depth of the microwave resonator-based sensor and b) the effect of permittivity variation of human tissues on the microwave resonator parameters

Adaptive coupling of resonators for efficient microwave heating of microfluidic systems

An electronically adaptive coupling technique is presented for a microwave microstrip resonator to improve the efficiency of liquid heating in a microfluidic system. The concept is based on feeding the resonator with two synchronized inputs that have a variable phase shift between them. A Wilkinson power divider and phase shifter were designed and fabricated for this purpose. Both simulation and measurement (using chloroform as an exemplar liquid) demonstrated that the adaptive coupling can be used to optimize the heating efficiency of the liquid

The biological effect of 2.45 GHz microwaves on the viability and permeability of bacterial and yeast cells

Microwaves are a form of non-ionizing radiation composed of electric (E) and magnetic (H) fields and are absorbed by biological tissues with a high water content. Our study investigated the effect of the E field, H field, and a combination of both (E + H) field’s exposure of structurally diverse micro-organisms, at a frequency of 2.45 GHz. We observed that the exposure to a microwave E field of an amplitude of 9.3 kV/m had no significant effect on cell viability; however, it did increase membrane permeability of Mycobacterium smegmatis to propidium iodide and to a range of different sized dextran particles in Escherichia coli, Staphylococcus aureus, Candida albicans, and M. smegmatis. The permeability of propidium iodide was observed in microwave treated cells (M. smegmatis) but not in heat-treated cells. Permeability of 3 kDa sized fluorescently labeled dextrans was observed across all cell types; however, this was found not to be the case for larger 70 kDa dextran particles. In terms of efflux, DNA was detected following E field exposure of M. smegmatis. In contrast, H field exposure had no effect on cell viability and did not contribute to increase cell’s membrane to dextran particles. In conclusion, this study shows that microwave generated E fields can temporarily disrupt membrane integrity without detrimentally impacting on cell viability. This approach has the potential to be developed as a high efficiency electropermeabilization method and as a means of releasing host DNA to support diagnostic applications