Detection of microorganisms using terahertz metamaterials

Abstract

Microorganisms such as fungi and bacteria cause many human diseases and therefore rapid and accurate identification of these substances is essential for effective treatment and prevention of further infections. In particular, contemporary microbial detection technique is limited by the low detection speed which usually extends over a couple of days. Here we demonstrate that metamaterials operating in the terahertz frequency range shows promising potential for use in fabricating the highly sensitive and selective microbial sensors that are capable of high-speed on-site detection of microorganisms in both ambient and aqueous environments. We were able to detect extremely small amounts of the microorganisms, because their sizes are on the same scale as the micro-gaps of the terahertz metamaterials. The resonant frequency shift of the metamaterials was investigated in terms of the number density and the dielectric constants of the microorganisms, which was successfully interpreted by the change in the effective dielectric constant of a gap area.

Effective Sensing Volume of Terahertz Metamaterial with Various Gap Widths

“…The transmission spectra of the uncoated metamaterials are plotted alongside for comparison (black line). The PMMA coating caused the resonant frequency to shift toward the red, which is due to the increased effective dielectric constant in the gap area of the metamaterials [2][3][4]11]. As expected, the frequency shift (Δf ) is higher for larger hPMMA.…”

“…As mentioned above, the resonant frequency of the THz metamaterials changes when dielectric materials are coated onto the metamaterial surface because of the change in the dielectric constant in the gap area. The resonant frequency shift can be explained by the following relationship: Δf/f0 ≈ α (ε PMMA -ε air)/ε eff [2,4], where α is the sensitivity coefficient, ε PMMA is the dielectric constant of PMMA, ε air is the dielectric constant of air, and ε eff (= neff 2 ) is the effective dielectric constant without the PMMA coating. In this work, we determined α to have a value of 0.22, whereas ε eff is known to have a value of 2.96 in the case of quartz [14].…”

“…Here, the LC resonant frequency can be easily controlled by manipulating the parameters C and L. For example, a change in the dielectric constant of the gap area causes a shift in the resonant frequency. Recently, we showed that THz metamaterials can work as sensitive on-site detectors for microorganisms with an extremely low density, both in ambient and aqueous environments [2,4]. The detection volume of metamaterial sensors is extremely confined in the vicinity of the gap area, providing enhanced sensitivity.…”

“…In recent years, metamaterials have been intensively studied because they have special properties beyond those of natural materials, such as negative refraction, super lensing, cloaking, perfect absorber, and sensing [1][2][3][4][5][6]. In the last decade, many types of metamaterial structures were suggested such as single split, double split, and electrical split ring resonators operating across various frequency ranges [7][8][9][10][11].…”

Differential Transmission Spectra of Terahertz Metamaterial Resonances for Sensing Microorganisms

“…최근 본 연구진은 테라헤르츠 영역에서 소 량의 미생물도 검출할 수 있는 고감도 메타물질 바이오 센서 를 제안하였다 [1] . 메타물질(metamaterial)은 일반적인 경우 금 속으로 만들어지는 인공구조이며 특정한 공진기 구조를 갖 게끔 제작된다.…”