Direct Writing of Microfluidic Three-Dimensional Photonic Crystal Structures for Terahertz Technology Applications

Highly Flexible Ti3C2Tx MXene/Waterborne Polyurethane Membranes for High-Efficiency Terahertz Modulation with Low Insertion Loss

The dynamic control of terahertz (THz) wave transmission on flexible functional materials is a fundamental building block for wearable electronics and sensors in the THz range. However, achieving high-efficiency THz modulation and low insertion loss is a great challenge while maintaining the excellent flexibility and stretchability of the materials. Herein, we report a Ti₃C₂T_x MXene/waterborne polyurethane (WPU) membrane prepared by a vacuum-assisted filtration method, which exhibits excellent THz modulation properties across stretching. The hydrophilic Ti₃C₂T_x MXene and WPU enable the uniform 3D distribution of Ti₃C₂T_x MXene in the WPU matrix. Particularly, the stretchability with the maximum strain of the membranes can reach 200%, accompanied by dynamic tuning of THz transmittance for more than 90% and an insertion loss as low as -4.87 dB. The giant THz modulation continuously decreases with MXene content per unit area, accompanied by a lower density of the MXene interface and diminished THz absorption during stretching. Such a design opens a pathway for achieving flexible THz modulators with a high modulation depth and low insertion loss, which would be used for THz flexible and wearable devices.

Electrochemical 3D printing of Ni-Mn and Ni-Co alloy with FluidFM

Additive manufacturing can realize almost any designed geometry, enabling the fabrication of innovative products for advanced applications. Local electrochemical plating is a powerful approach for additive manufacturing of metal microstructures; however, previously reported data have been mostly obtained with copper, and only a few cases have been reported with other elements. In this study, we assessed the ability of fluidic force microscopy to produce Ni-Mn and Ni-Co alloy structures. Once the optimal deposition potential window was determined, pillars with relatively smooth surfaces were obtained. The printing process was characterized by printing rates in the range of 50-60 nm s^-1. Cross-sections exposed by focused ion beam showed highly dense microstructures, while the corresponding face scan with energy-dispersive x-ray spectroscopy spectra revealed a uniform distribution of alloy components.

Label-free detection of living cervical cells based on microfluidic device with terahertz spectroscopy

Early diagnosis of cervical cancer is essential for a good prognosis. Terahertz wave detection technology is a nondestructive and label-free physical detection technology, which can detect and monitor the cancer cells in real time, especially for patients with deep or inaccessible tumors. In this study, a single-cell-layer microfluidic device was developed. After replacing the optical clearing agent, the characteristics of H8, HeLa and SiHa cell lines in adherent and suspended states were detected. Additionally, the absorption increased with increasing cell density. For the mixed suspension cell samples, principal component analysis-support vector machine method was used to identify benign and malignant cell component. After living cells formaldehyde, changes in cell membrane permeability were evaluated to identify the cell survival status (i.e., dead or living) based on terahertz spectroscopy amplitude differences. Therefore, extending the terahertz spectrum detection to the molecular level can characterize the life essence of cells and tissues.

Optical-Transparent Self-Assembled MXene Film with High-Efficiency Terahertz Reflection Modulation

The modulation of the terahertz (THz) wave is fundamental for its applications in next-generation communications, biological imaging, sensing, and so forth. Searching for higher efficient modulation is still in progress, although plenty of materials have been explored for tuning THz wave. In this work, optical-transparent self-assembled MXene films are used to modulate the THz reflection at the SiO₂/MXene/air interface based on the impedance matching mechanism. By adjusting the number of stacked MXene layers/concentrations of MXene dispersions, the sheet conductivity of the MXene films will be changed so that the impedance at the SiO₂/MXene/air interface can be tuned and lead to a giant modulation of THz reflection. Particularly, we demonstrate that the MXene films have highly efficient THz modulation from antireflection to reflection-enhancing with a relative reflection of 27% and 406%, respectively. This work provides a new pathway for developing the MXene films with the combination of optical-transparency and high smart THz reflection characteristics, and the films can be applied for THz antireflection or reflection-enhancing.