Their differences were successfully interpreted in terms of their cell wall composition. Recently, we discovered that microorganisms can be classified in terms of their dielectric properties in other words, the dielectric constants of bacteria are higher than those of molds, whereas yeasts exhibit particularly high values that are greater than that of water 28. Because metamaterial sensing is dielectric sensing, obtaining information regarding the dielectric constant of the target substances is the primary step for the practical application of the sensors 21, 22, 23, 24, 25, 26, 27. Recently, terahertz (THz) metamaterials have been introduced as a real-time and sensitive platform for detecting biological substances including microorganisms 15, 16, 17, 18, 19, 20. Therefore, true label-free diagnostic tools that exploit their inherent physical properties without requiring fluorescent labeling should be developed. By contrast, alternative microbial detection techniques such as fluorescence microscopy and flow cytometry require fluorescent materials to efficiently detect microorganisms 11, 12, 13, 14. Nevertheless, PCR is generally labor intensive and time consuming owing to its multiple procedures additionally, it requires target-specific agents and pretreatment to extract DNA from microorganisms 7, 8, 9, 10.

Polymerase chain reaction (PCR) techniques have been widely adopted for their identification, as it can detect various infectious bacteria with high fidelity 3, 4, 5, 6.

In the era of global pandemics, demand for the development of rapid and accurate tools is increasing for the identification of pathogens such as bacteria and viruses for the effective treatment of deadly diseases and the prevention of infections 1, 2. Finally, we perform THz melting curve analysis on the mixture of bacterial species in which the pathogenic bacteria are successfully distinguished from each other, which is essential for practical clinical and environmental applications such as in blood culture. In addition, we can distinguish gram-negative bacteria from gram-positive bacteria which show strong peaks in the temperature range of cell wall destruction. Differential thermal curves obtained from the temperature-dependent resonance exhibit the peaks consistent with bacterial phases, such as growth, thermal inactivation, DNA denaturation, and cell wall destruction. The resonant frequency of the metasensor coated with a bacterial layer changes as a function of temperature this provides a unique fingerprint specific to the individual microbial species without the use of fluorescent dyes and antibodies. In this study, we perform a thermal curve analysis with terahertz (THz) metamaterials to develop a label-free identification tool for pathogens such as bacteria and yeasts.

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