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.

The piezoelectric vibration energy harvester (PVEH) based on the variable cross-section cantilever beam (VCSCB) structure has the advantages of uniform axial strain distribution and high output power density, so it has become a research hotspot of the PVEH. However, its electromechanical model needs to be further studied. In this paper, the bidirectional coupled distributed parameter electromechanical model of the MEMS VCSCB based PVEH is constructed, analytically solved, and verified, which laid an important theoretical foundation for structural design and optimization, performance improvement, and output prediction of the PVEH. Based on the constructed model, the output performances of five kinds of VCSCB based PVEHs with different cross-sectional shapes were compared and analyzed. The results show that the PVEH with the concave quadratic beam shape has the best output due to the uniform surface stress distribution. Additionally, the influence of the main structural parameters of the MEMS trapezoidal cantilever beam (TCB) based PVEH on the output performance of the device is theoretically analyzed. Finally, a prototype of the Aluminum Nitride (AlN) TCB based PVEH is designed and developed. The peak open-circuit voltage and normalized power density of the device can reach 5.64 V and 742 μW/cm³/g², which is in good agreement with the theoretical model value. The prototype has wide application prospects in the power supply of the wireless sensor network node such as the structural health monitoring system and the Internet of Things.

This paper presents a novel chemical sensor using a metamaterial absorber, which is composed of an Au Bottom layer, a microfluidic channel, a FR4 substrate and a split-square-cross-resonator (SSCR). The resonance generated by SSCR is extraordinarily sensitive to changes of the effective dielectric constant around the capacitive gap. Furthermore, the effective dielectric constant of the dielectric substrate is under the influence of microfluidic channels by using an infinitesimal quantity of a liquid. The proposed sensor exhibits an outstanding sensitivity by a creative SSCR structure and the Au Bottom layer. In addition, the relationship between the absorption frequency and chemical concentration is demonstrated by simulation.

This paper presents a novel metamaterial micro-fluidic sensor with two pairs of symmetrical double split-ring resonators (DSRR) compared to state of the art, which exhibits unique high-Q (~653) resonance and a 34% higher S21 magnitude than a single DSRR and allow, for the first time, real-time dual-channel biochemical testing through the design of two micro channels underneath the metamaterial DSRR. Polyimide was chosen as the substrate material and it shows good temperature stability at -200~300 °C, which makes the sensor enabling to work in harsh environment.