Borwen You

Pore-size dependent THz absorption of nano-confined water.

We performed a THz absorption spectroscopy study on liquid water confined in mesoporous silica materials, MCM-41-S-18 and MCM-41-S-21, of two different pore sizes at room temperatures. We found that stronger confinement with a smaller pore size causes reduced THz absorption, indicating reduced water mobility due to confinement. Combined with recent theoretical studies showing that the microscopic structure of water inside the nanopores can be separated into a core water region and an interfacial water region, our spectroscopy analysis further reveals a bulk-water-like THz absorption behavior in the core water region and a solid-like THz absorption behavior in the interfacial water region.

Pilot clinical study to investigate the human whole blood spectrum characteristics in the sub-THz region.

We have conducted a pilot clinical study to not only investigate the sub-THz spectra of ex-vivo fresh human whole blood of 28 patients following 8-hours fasting guideline, but also to find out the critical blood ingredients of which the concentration dominantly affects those sub-THz spectra. A great difference between the sub-THz absorption properties of human blood among different people was observed, while the difference can be up to ~15% of the averaged absorption coefficient of the 28 samples. Our pilot clinical study indicates that triglycerides and the number of red blood cells were two dominant factors to have significant negative correlation to the sub-THz absorption coefficients.

Terahertz artificial material based on integrated metal-rod-array for phase sensitive fluid detection

Transverse-electric (TE) polarized terahertz (THz) waves along a three-layered metal-rod-array (MRA) are demonstrated to identify liquid molecular dipole moments based on the extended optical-path-Iengths. The minute sensing ability is less than 0.1 mmol, equaling

Sensitivity analysis of multilayer microporous polymer structures for terahertz volatile gas sensing

2.7 mu mathbf{mol}/mathbf{mm}^{2}

High Sensitivity of T-Ray for Thrombus Sensing.

adsorption density.

Terahertz plasmonic waveguide sensing based on metal rod array structures

The sensitivity of multilayer microporous polymer structures (MPSs) for in situ and label-free organic vapor sensing is investigated in terahertz frequency. The porous structure provides a large hydrophilic surface area and numerous micropores to adsorb or fill polar vapors, thereby leading to greatly enhanced wave-analyte interaction with an apparent terahertz signal change. Different configurations of MPS with distinct geometric parameters are fabricated to study the structure-dependent sensitivity. The signal responses from the acetone-vapor-filled MPS, represented as effective absorption coefficient and refractive index variation, are proportional to the amounts of vaporized molecules. The responsivity is independent of MPS stacking configuration but can be significantly improved by decreasing the micropore volume. The linear responsivity range for the acetone vapor concentration is as wide as 200 ppm, and the detection limit can be as low as 1 ppm corresponding to the molecular density of 31 pmol/mm3. Different concentrations of toxic methanol adulterated in alcoholic aqueous solutions are successfully identified in their vapor phase by using the MPS-based terahertz sensor with an optimal sensitivity.

Characteristics of metal-grating-integrated tapered parallel-plate terahertz waveguides

Atherosclerotic plaque rupture or erosion and subsequent development of platelet-containing thrombus formation is the fundamental cause of cardiovascular disease, which is the most common cause of death and disability worldwide. Here we show the high sensitivity of 200–270u2009GHz T-ray to distinguish thrombus formation at its early stage from uncoagulated blood. A clinical observational study was conducted to longitudinally monitor the T-ray absorption constant of ex-vivo human blood during the thrombus formation from 29 subjects. Compared with the control group (28 subjects) with uncoagulated blood samples, our analysis indicates the high sensitivity of 200–270u2009GHz T-Ray to detect thrombus with a low p-valueu2009<u200910−5. Further analysis supports the significant role of platelet-activated thrombotic cascade, which modified the solvation dynamics of blood and occurred during the early coagulation stage, on the measured T-Ray absorption change. The ability to sense the thrombus formation at its early stage would hold promise for timely identification of patients at risk of various atherothrombotic disorders and save billions of lives.

Frequency-dependent skin penetration depth of terahertz radiation determined by water sorption–desorption

Metallic rod array is successfully demonstrated to be integrated a parallel plate waveguide and used as a slab-waveguide for sensing applications. Both the waveguide properties are characterized from the transmission spectra using different polarization conditions of terahertz electromagnetic fields, which are parallel and perpendicular to the rod axis. When THz field polarization is parallel to the rod axis, there is high-pass filtering feature with structure-period-dependent threshold frequency, corresponding to the plasma frequency of the rod-array composite. For the polarization perpendicular to the rod axis, there is Bragg diffraction frequency as forbidden band with considerably low transmission power. The metal-rod-array integrated parallel-plate waveguide is connected with a microfluidic channel to sense liquids, and the minimum detectable quantity is about 13μmol/mm3. The metal-rod-array slab waveguide is able to sense thinfilm with nanometer level, and the detectable optical path difference is down to λ/2380. The sensor properties of multiple functions for sensing various analyte conformations, microfluidic integration and high sensitivity would be applied in biomedicine and biochemical applications.