Simultaneous on-chip sensing of multiple greenhouse gases in a complex gas environment is highly desirable in industry, agriculture, and meteorology, but remains challenging due to their ultralow concentrations and mutual interference. Porous microstructure and extremely high surface areas in metal-organic frameworks (MOFs) provide both excellent adsorption selectivity and high gases affinity for multigas sensing. Herein, it is described that integrating MOFs into a multiresonant surface-enhanced infrared absorption (SEIRA) platform can overcome the shortcomings of poor selectivity in multigas sensing and enable simultaneous on-chip sensing of greenhouse gases with ultralow concentrations. The strategy leverages the near-field intensity enhancement (over 1500-fold) of multiresonant SEIRA technique and the outstanding gas selectivity and affinity of MOFs. It is experimentally demonstrated that the MOF-SEIRA platform achieves simultaneous on-chip sensing of CO 2 and CH 4 with fast response time (<60 s), high accuracy (CO 2 : 1.1%, CH 4 : 0.4%), small footprint (100 × 100 µm 2), and excellent linearity in wide concentration range (0-2.5 × 10 4 ppm). Additionally, the excellent scalability to detect more gases is explored. This work opens up exciting possibilities for the implementation of all-in-one, real-time, and on-chip multigas detection as well as provides a valuable toolkit for greenhouse gas sensing applications.

Surface-enhanced infrared absorption (SEIRA) spectroscopy is a powerful technique that overcomes the issue of low molecular absorption cross-sections in infrared spectroscopy. Due to the collective oscillations of electrons in the infrared regime, SEIRA using resonant metamaterial provides greatly enhanced (up to 10 7 ) electromagnetic fields extending up to tens of nanometers from the metamaterial. The enhanced near-field enables spectroscopic analysis and ultrasensitive on-chip sensing of molecules. This interesting characteristic has aroused widespread attention from researchers to SEIRA technology, and various SEIRA-based sensing applications have been continuously emerging. Optimization of the signal enhancement to obtain high sensing performance is the developing main thread of SEIRA technology. In this Review, we provide a basic understanding of SEIRA's sensing mechanism and theoretical model. With this background, several SEIRA optimizing methods are discussed, ranging from design, materials to algorithms. Additionally, perspectives about the future development trends of SEIRA technologies are discussed.

Metamaterial absorbers have proven their ability to sense in the terahertz domain. However, the sensitivity is always limited by the poor spatial overlap between the analyte and the localized enhanced electromagnetic field. Here, we try to tackle this challenge by utilizing an absorber with a bilayer cross-shaped plate-hole structure to ingeniously excite hot-spots covering the analyte. As a result, the sensitivity is significantly improved, theoretically about 7 and 18 times higher than that of the conventional cross-shaped absorber and its complementary cross-shaped absorber, respectively. We then experimentally demonstrate its ability to quantitatively detect biotin with a sensitivity of 153 GHz/μM, higher than that of previously reported biotin sensors. Additionally, the polarization-independent nanostructure decreases the design and fabrication complexity and maintains high reflection at a wide range of incident angles over ±50°. These findings open up opportunities for metamaterial absorbers to realize ultrasensitive biosensing in the fingerprint region of the terahertz regime.

The novel coronavirus (COVID-19) is spreading globally due to its super contagiousness, and the pandemic caused by it has caused serious damage to the health and social economy of all countries in the world. However, conventional diagnostic methods are not conducive to large-scale screening and early identification of infected persons due to their long detection time. Therefore, there is an urgent need to develop a new COVID-19 test method that can deliver results in real time and on-site. In this work, we develop a fast, ultra-sensitive, and multi-functional plasmonic biosensor based on surface-enhanced infrared absorption for COVID-19 on-site diagnosis. The genetic algorithm intelligent program is utilized to automatically design and quickly optimize the sensing device to enhance the sensing performance. As a result, the quantitative detection of COVID-19 with an ultra-high sensitivity (1.66%/nm), a wide detection range, and a diverse measurement environment (gas/liquid) is achieved. In addition, the unique infrared fingerprint recognition characteristics of the sensor also make it an ideal choice for mutant virus screening. This work can not only provide a powerful diagnostic tool for the ultra-rapid, label-free, and multi-functional detection of COVID-19 but also help gain new insights into the field of label-free and ultrasensitive biosensing.

The past few decades have witnessed the tremendous progress of human–machine interface (HMI) in communication, education, and manufacturing fields. However, due to signal acquisition devices’ limitations, the research on HMI related to communication aid applications for the disabled is progressing slowly. Here, inspired by frogs’ croaking behavior, a bionic triboelectric nanogenerator (TENG)‐based ultra‐sensitive self‐powered electromechanical sensor for muscle‐triggered communication HMI application is developed. The sensor possesses a high sensitivity (54.6 mV mm−1), a high‐intensity signal (± 700 mV), and a wide sensing range (0–5 mm). The signal intensity is 206 times higher than that of traditional biopotential electromyography methods. By leveraging machine learning algorithms and Morse code, the safe, accurate (96.3%), and stable communication aid HMI applications are achieved. The authors' bionic TENG‐based electromechanical sensor provides a valuable toolkit for HMI applications of the disabled, and it brings new insights into the interdisciplinary cross‐integration between TENG technology and bionics.

MicroRNAs play an important role in early development, cell proliferation, apoptosis, and cell death, and are aberrantly expressed in many types of cancers. To understand their function and diagnose cancer at an early stage, it is crucial to quantitatively detect microRNA without invasive labels. Here, a plasmonic biosensor based on surface‐enhanced infrared absorption (SEIRA) for rapid, label‐free, and ultrasensitive detection of miR‐155 is reported. This technology leverages metamaterial perfect absorbers stimulating the SEIRA effect to provide up to 1000‐fold near‐field intensity enhancement over the microRNA fingerprint spectral bands. Additionally, it is discovered that the limit of detection (LOD) of the biosensor can be greatly improved by using tetrahedral DNA nanostructure (TDN) as carriers. By using near‐field enhancement of SEIRA and specific binding of TDN, the biosensor achieves label‐free detection of miR‐155 with a high sensitivity of 1.162% pm−1 and an excellent LOD of 100 × 10−15 m. The LOD is about 5000 times lower than that using DNA single strand as probes and about 100 times lower than that of the fluorescence detection method. This work can not only provide a powerful diagnosis tool for the microRNAs detection but also gain new insights into the field of label‐free and ultrasensitive SEIRA‐based biosensing.

Multifunctional chemical sensing is highly desirable in industry, agriculture, and environmental sciences, but remains challenging due to the diversity of chemical substances and reactions. Surface-enhanced infrared absorption (SEIRA) spectroscopy can potentially address the above problems by ultra-sensitive detection of molecular fingerprint vibrations. Here, a multifunctional chemical sensing platform based on dual-resonant SEIRA device for sensitive and multifunctional on-chip detection of poly(ethyl cyanoacrylate) (PECA) is reported. It is experimentally demonstrated that the SEIRA sensing platform achieves multiple functions required by the PECA glue industry, including vibrational detection, thickness measurement, and in situ observation of polymerization and curing, which are usually realized by separately using a spectrometer, a viscometer, and an ellipsometer in the past. Specifically, the all-in-one sensor offers a dual-band fingerprint vibration identification, sub-nm level detection limit, and ultrahigh sensitivity of 0.76%/nm in thickness measurement, and second-level resolution in real-time observation of polymerization and curing. This work not only provides a valuable toolkit for ultra-sensitive and multifunctional on-chip detection of PECA, but also gives new insights into the SEIRA technology for multi-band, multi-functional, and on-chip chemical sensing.

An immunochromatographic strip is an effective diagnostic tool in various fields because of its simplicity, rapidity, and cost-effectiveness. However, typical strips for preliminary screening provide only qualitative or semiquantitative results, and common solutions for quantitative detection by incorporating different kinds of nanoparticles as biomarkers still do not solve this problem thoroughly. Here, we try to tackle this challenge by integrating low-cost membrane-compatible square split-ring resonators and structure-design-flexible microchannels with flexible strips. We experimentally demonstrate that the limit of detection (LOD) and sensitivity of the strip for quantitative detection of Staphylococcus aureus reach 0.784 ng/mL and 10.214 MHz/(ng/mL), respectively. The LOD level is about 63 times higher than that of the color-based strip determined by the naked eye, and the stability is about 18 times higher than that of the fluorescent strip. This work could not only provide a powerful diagnosis tool for the quantitative detection of S. aureus or other molecules but also deliver new avenues for achieving electric field detection of biomolecules, system-level integration of biosensors, and the development of portable diagnostic devices.