Lei Han

Skin converts multisensory stimuli into bioelectrical signals through cutaneous receptors and then transmits them to the central nervous system (CNS), implementing an analog-digital response to perceive the environment. However, target engagement components that access multisensory stimuli face significant challenges in multimodal interaction, especially the intrinsic decoupling in stretchable heterogeneous integrating systems and the dimensional broadening in traditional human five sensations. In this work, we propose a passive wireless multimodal self-decoupling methodology paradigm to optimize the signal scheduling of systems and broaden the cognitive dimensions of humans, which engages the strategic configuration of symmetrical inductor-capacitor (LC) resonant circuit combined with LC tank to unlock the single-port output self-decoupling sensing, thereby decoding five sensible stimuli to augment situational awareness of human. Systematic theoretical model is established to verify the self-decoupling methodology and the multimodal sensing scheme based on RLC-modulated mechanism. Multiple prototypes of single-port liquid metal (LM)-based wireless multimodal electronic skin implement targeted responses of skin-like receptors. That incorporating pressure (0 kPa~40 kPa), temperature (25 °C ~ 45 °C), humidity (5%RH ~ 90%RH), ultraviolet (0 lm~20 lm) and inclination (30°, 45°, 60°, 90°) through accessing corresponding sensing components. This technique proposal is designed to render a self-decoupling methodology for stretchable wireless multimodal unperturbed platforms and bridge the spatial sensory dimensions in traditional multisensory mechanisms for human-machine interaction.

In this paper, an innovative reconfigurable microstrip RF device design method is proposed, which is inspired by origami structures. The experimental results of the reconfigurable low-pass filter indicate that the maximum origami folding height is 3 mm, resulting in the frequency tuning range of the filter being 524~568 MHz, the return loss is below −15.0 dB and the insertion loss is below 2.5 dB up to 500 MHz. It is demonstrated that the proposed design method for reconfigurable microstrip RF devices is fairly effective through theoretical and experimental research. This work provides a groundbreaking method for reconfigurable RF devices with origami structures.

Parity-time (PT) symmetric resonators have an exact phase with real frequency eigenvalues and a broken phase with complex-conjugate frequency eigenvalues. In the presence of nonlinear gain, the PT-symmetric resonator exhibits nonreciprocal transmission when it is biased at the broken phase, which promises applications for isolators and circulators in modern communication systems. The nonlinear distortion performance is one of the most important metrics in most electronic applications where linearity is critical. This article provides the first experimental results of nonlinear distortion of nonreciprocal transmission in a pair of electrically coupled silicon micromechanical resonators at the broken phase. The results show the 1 dB gain compression point (P1dB) with 5 dBm and the input-referred third-order intercept point (IIP3) with 11.5 dBm.

Skidding, as a result of freezing on highway road pavements, significantly affects driving safety. The freezing point is contingent upon the salt concentration in standing water on road pavements. To facilitate early warnings, the freezing point is commonly estimated via real-time, in situ monitoring of water conductivity. This article presents an empirical conductivity model that encompasses seven fitting parameters to delineate the relationship between conductivity, salt concentration, and temperature over a broad range of conductivity. The model demonstrates that conductivity values up to 20.7 S/m exhibit the maximum average relative deviation (dp ≤ 2.2%) and the goodness-of-fit (R² > 0.991) in comparison with experimental data of the CaCl₂ solution. A four-electrode cell for measuring the conductivity is optimized through a finite-element analysis program to accommodate a wide range of conductivity and packaged into polyether ether ketone (PEEK) to withstand the road environment conditions. The excitation and detection circuit are designed and simulated using a circuit simulation program to suppress polarization effects and improve measurement accuracy. By using a cubic spline interpolation algorithm, the measured conductivity is initially converted to the salt concentration and then to a freezing point. The four-electrode cell, its processing circuit, and a Pt resistance temperature sensor which provides compensation of conductivity measurements caused by temperature variation, are all encapsulated into a polyphenylene oxide (PPO) substrate and an aluminum alloy shell. Experimental results demonstrate that the sensor can predict a wide range of freezing points from -30 °C to 0 °C.

Hydroplaning, as a result of water films on highway pavements, poses a significant threat to driving safety. Consequently, real-time, cost-effective in situ monitoring of water film thickness on road surfaces is crucial for early warning systems. Microwaves, when transmitted through water, undergo substantial phase delays, from which the thickness of the water film can be deduced. We have developed an equivalent impedance model to measure the water film thickness, based on transmission line theory. The amplitude and phase of microwave reflection signals that traverse the water film have been analytically determined. For validation purposes, both electromagnetic and circuit simulations were conducted. To facilitate this, processing circuits for a microstrip antenna and a phase detector were integrated onto printed circuit boards (PCBs). The entire measurement system, encompassing the microstrip antenna and RF (radio frequency) PCBs, was packaged using a polyphenylene oxide (PPO) substrate and an aluminum alloy shell. Experimental results demonstrate that this system can accurately measure water film thicknesses of up to 7 mm at a frequency of 2.4 GHz. Notably, the measured water film thickness displayed a variance of less than 0.1 mm in comparison with a high-precision profilometer.

Severe weather such as rainstorm significantly increases the wetness of expressway pavement, which seriously affects road traffic safety. Therefore, achieving low-cost, high-performance, and real-time monitoring of water film thickness can help reduce the risk of traffic accidents. Sensors based on spectral intensity method, resonance method, and other methods are limited by cost, performance, and integrated applications. Therefore, this paper adopts the principle of microwave signal reflection to achieve a water film thickness sensor with large range, high accuracy, and high resolution. The electromagnetic simulation and parameter optimization on the water film thickness sensor has been initially conducted, followed by the design of a phase-reconfigurable circuit structure. This structure is designed to endow the phase difference voltage curve output by the sensor with characteristics of interlaced symmetric axes and complementary slopes, thereby significantly enhancing the detection accuracy and resolution of the sensor. Experimental results demonstrate that the water film thickness sensor designed in this study achieves a measurement range up to 7 mm, with an accuracy reaching 0.05 mm and a resolution as high as 0.005 mm.

In this paper, we report a novel three-state Radio Frequency Microelectromechanical Systems (RF MEMS) switch, which is based on origami structure for large tunable capability. Combined with the origami structure, the switch can achieve the deep-on state by raising the height of the origami beam. This switch has been designed and fabricated successfully with the silicon process. Experimental results show that the origami beam can be raised to $76~\mu $ m at the deep-on state with an amplification factor of 12.6 compared to the on state. In the frequency range of 10-30 GHz, when the switch is at the on state, the insertion loss is better than −0.4 dB and the return loss is better than -18dB. At the deep-on state, the return loss achieves −31dB with the improvement of 13 dB. At the off state, the isolation of the switch is better than −20 dB. As a result, the presented switch based on origami structure can be a promising choice for low loss, high isolation, and large tunable range applications.[2024-0221]

With the rapid development of the Internet of Things, sustainable energy supply and wireless transmission of distributed wireless sensor nodes have become a challenge. In recent years, self-powered wireless sensing technologies (SWSTs) combining triboelectric nanogenerators (TENG) and wireless solutions have been proposed to address the issues of energy harvesting and wireless transmission. This review systematically summarizes the research advances in SWSTs based on TENG, and compares the advantages and disadvantages of different technologies. In addition, challenges and expectations for future TENG-based SWSTs are discussed as well.