Nanometric metal wire as a guide for THz investigation of living cells

Abstract

The development of microsystems as tools for nanotechnology is strongly observed in the case of Biological MicroElectroMechanical Systems (BioMEMS). A part of them aim at the characterisation of biomolecules in solutions or in biological entities such as living cells. THz spectroscopy could provide interesting new complementary information at the systemic biology due to its faculty to probe the low binding energy between molecules or inside heavy biomolecules. We describe here a THz BioMEMS based on a new integrated propagation mode around a metallic wire where the radial size is down to the nanometre scale. This size is required for a sub-micrometre spatial resolution. We give the first results obtained in term of propagation constant and permittivity sensitivity. They are the key for an optimised configuration of THz nanoprobe. He is currently in PhD thesis and he works on the development of the THz BioMEMS (Biological MicroElectroMechanical System) for new investigations in life science, especially on single biological cells. Its research involves THz electromagnetic propagation and microfluidic circulation. He has demonstrated recently that a propagation of THz surface waves is possible on nanometre metallic wires.Bertrand Bocquet was received the MSc Degree in Physics in 1984, the PhD thesis in Electronics in 1989 and the Habilitation à Diriger des Recherches in 1999. From 1989 to 2000, he was an Assistant Professor at the Sciences and Technologies University of Lille. Its research interests were the medical imagery based on the near field microwave radiometry for the detection and characterisation of breast cancers and the real-time radiometric cameras at millimetre waves for defence and transportation safety. Electromagnetic -matter interactions, electromagnetic computation and inverse problems were involved in this research domain. Since 2000, he has been a Professor at the same university where he works on the interaction between THz waves and biological entities by using original microfluidic biosensors. Nanometric metal wire as a guide for THz investigation of living cells 785His researches include the fabrication of innovative microsystems with new materials, the design of THz integrated circuits and the characterisation of biological entities in liquid phase. This activity is supported by local and national grants. He heads the Microfluidic Microsystems and THz group (M²T). He is author or co-author of more than 100 international papers and communications, two book chapters and two patents. He is currently promoter of three PhD thesis.

Terahertz Interferometer for Integrated Goubau-Line Waveguides

“…Its permittivity is ε r and its length is l = 1 mm. The electromagnetic field confinement around the PGL is about 10 µm for a 1 µm-wide PGL at 250 GHz [8]. Thus, in this simulation, the electromagnetic field is expected to be confined in Figure 5.…”

“…For instance, THz waves can be driven in a plasmon-like mode by a single metallic wire [7]. When this waveguide is made of a single wire deposited on a substrate, it is called "Planar Goubau Line" (PGL) and can reach spatial field-confinement down to several micrometers [8]. Such a configuration has already been integrated in biochips [9] to characterize enzymatic reactions [10] or molecule hydration [11].…”

Terahertz Spiral Planar Goubau Line Rejectors for Biological Characterization

“…THz polarization is radial, in a quasi-TEM mode, and strongly confined. Indeed, study of propagation on nanometric wires (down to 100 nm) shows a micrometer-scale wave-confinement without influence on propagation parameters [10]. Experimentally, one of the main challenges concerns the Goubau mode excitation.…”

“…However, we have shown that the resonator size can be decreased again by increasing the turns number. Wire size can be thinned down to the nanometer range without strong electromagnetic-properties damage [10]. Figure 12 shows the frequency response obtained with a 2.5 µm-wide wire, in a 4-turn spiral topology, with a 2.5 µm gap.…”

“…It can be achieved by integrating planar waveguides in hyperfrequency-electronic circuits [9]. For higher frequencies, we have already demonstrated that THz propagation on metallic nano-wires is possible [10]. The combination of such a waveguide with microfluidic circuits allows us to perform THz measurements on aqueous solutions with high reproducibility and sensitivity.…”