This work presents the noncontact immobilization of Ti 3 C 2 T x MXene on a planar microwave resonator sensor via a polyimide film to enhance the gas detection sensitivity, enabling the characterization of the part per million-level of acetone gas. Sandwiching a polyimide (PI) film confined an intense electromagnetic field between the resonator’s interdigital capacitor structure and the MXene layer, maintaining a significant interaction between the acetone gas molecules and the resonator’s EM field via the MXene layer. Therefore, contactless immobilization of the MXene layer enhanced the acetone gas detection sensitivity by 110% compared to the resonator gas sensor with MXene deposited directly on the resonator surface. As a proof of concept , two sensor prototypes were implemented using resonators with layers of PI film and MXene and resonators with MXene only and were applied to detect a wide range of acetone gas concentrations. Immobilizing the layers of PI film and MXene on the microwave resonator achieved a linear correlation between the resonant frequency and acetone gas concentration with high sensitivity (17.85 kHz/ppm, a fast response time (60 s), and recovery time (85 s).
Microwave sensors based on microstrip antennas are promising as wearable devices because of their flexibility and wireless communication compatibility. However, their sensitivity is limited due to the reduced sensor size and the potential of biochemical monitoring needs to be explored. In this work, we present a new concept to enhance the microwave signals using nanostrip-based metamaterials. The introduction of the nanostrip structures was achieved by theory and simulations. Experiments prove their enhancement of the electric field and sensing response in the characteristic gigahertz (GHz) wave band. Ordered nanostrips were fabricated on a plastic substrate through a simple nanoscale printing approach. Glucose oxidase is directly doped into the nanostrips, which enables a flexible wearable enzymatic biosensor for glucose sensing. Sensing experiments demonstrated that the nanostrip biosensor gives excellent performance for glucose detection, including high sensitivity, fast response, low detection limit, high affinity, and low power consumption. The applicability of the nanostrip-based sensor as a wearable epidermal device for real-time noninvasive monitoring of glucose in sweat is verified as well.
Jie Wei,En-Kang Wu,Ji-Hao Zhang,Zhen Zhang,Xiao-Cong Tang,Tian Qiang,Yong-Woo Jang,Xiao-Feng Gu,Meng Zhao,Svetlana von Gratowski,Jun-Ge Liang,Ming-Yang Yan,Cong Wang
Acetone sensors continue to command significant attention as a robust platform for emissions control, industrial safety monitor, and diagnostic analysis of human exhaled gas for diabetes monitoring. This study presents the design and fabrication of an ultra-narrowband, interdigital capacitor (IDC)-based three-level split ring resonator (TSRR) microwave gas sensor for rapid acetone detection. MXene-TiO 2 composites with varying mass ratios were deposited onto the resonator surface to evaluate the gas-sensitive properties of TiO 2 /MXene materials across acetone concentrations of 10–500 ppm. Results demonstrate that the microwave acetone sensor incorporating the TiO 2 /MXene (3 wt%) composite exhibits exceptional performance: high sensitivity (1544 mdB/ppm), rapid response and recovery durations (130 s and 140 s, respectively), superior selectivity, and excellent stability under high-humidity conditions—significantly surpassing existing microwave gas sensors. Furthermore, the gas-sensing mechanism was elucidated through impedance-matching circle diagrams corresponding to varying acetone concentrations. MXene materials, renowned for their expansive specific surface area, exhibit considerable promise in gas sensing applications, particularly for room-temperature acetone detection with high selectivity and sensitivity extending to ppb concentrations. This investigation introduces a novel paradigm for room-temperature acetone gas detection, as evidenced by the development of triboelectric plasma-regulated high-sensitivity sensors.
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