Metamaterial-based Sensors

Abstract

In genetic diagnostics, analysis is mostly based on fluorescent labelling of target DNA molecule and sequences. The process of labelling can alter DNA strands, is not always specific enough to make gene detection sufficiently precise and is time consuming and expensive. For Point-of-Care or benchtop diagnostics, there is a technological requirement for reading the labels, again slowing down the process and making devices more complex and expensive. To get around these shortages, this study introduces a label-free detection technique using metamaterials.

Metamaterials are synthetic composite materials, engineered to have electromagnetic properties that do not occur in nature. Metamaterials can demonstrate resonant behaviours and localize the electromagnetic field. This can be used to improve the sensitivity of surface based sensors, which respond to refractive index changes in the deposited material. In addition, the metamaterials allow for tunability of the resonant frequency, so that sensors can be targeted to specific responses, such as the THz sensitivity of DNA. This work focuses on the designs and fabrication of metamaterial structures for the purpose of sensing. The metamaterial inclusions are micrometre scaleX-shaped resonators, each on a 220×220µm square base, tuned to produce trapped-mode resonance interahertz (THz) regime (0.4-1.2THz) to detect backbone resonances of DNA which occur in this region.

Research indicates that modification of asymmetry in the shape of resonators, causes them to resonate at two different frequencies close to one another, the trapped mode in between the two gives a sharp notch with a high quality factor (Q-factor), ideal for sensing purposes. The Q-factor of the trapped-mode resonance produced using this metamaterial is shown to be higher than the previously proposed metamaterial-based biosensors investigated by other researchers.

The fabricated metamaterials show a good agreement between the simulated and measured results. Also, fabrication results show that by adding an analyte, layered up on top of the metamaterial inclusions, the sensitivity of the structure can be calculated by examining the change in the trapped-mode resonance frequency, where a shift in the peak of resonance is observed and quantified.

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