Single Sensor Structure Research Articles

Electromechanically stable and flexible poro-hyperelastic composites for multimodal robotic tactile sensing

The expansion of automated production places increased demands on intelligent sensory networks for collecting and processing various input signals, which necessitate higher standards for multimodal detection, sensitivity, and sensing response speed. Here, this work developed a poro-hyperelastic composites-based multimodal tactile sensor capable of triboelectric, piezoresistive, and capacitive modes across multiple strains and frequency domains. Such the multilayered flexible multimodal mechano-electronic sensor (MMES) is constructed from a carbon nanotubes porous sponge (CNPS), facilitating switching between trimodal sensing modes integrated within a single sensor structure, effectively enhancing the electromechanical robustness of the sensory system. The present MMES sensor exhibits excellent pressure sensing performances, with a wide range (0–20 kPa), fast response (less than 102 ms in piezoresistive mode and less than 62 ms in capacitive mode), high sensitivity (up to 0.12 V/kPa⁻1 in triboelectric mode), and long-term durability (exceeding 10,000 cycles). Moreover, a micro-CT generated 3D model was established using finite element analysis (FEA) to investigate porous hyperelastic behaviours of the CNPS composites, in agreement with experimental data. The results demonstrated that the MMES sensor is particularly suitable for dynamic feedback in robotic arms, allowing production lines to make accurate distinguishments and operations by sensing distinct materials and resistances encountered during assembly in real time. The outcomes offer promising applications of multimodal robotic tactile sensing for human-machine interaction.

Interrogation technique analyses of a hybrid fiber optic sensor based on SPR and MMI.

This study evaluates the interrogation techniques of a hybrid fiber optic sensor based on surface plasmon resonance (SPR) and multimode interference (MMI). The sensor is based on a single mode, fiber-no core, fiber-single mode fiber (SMF-NCF-SMF) structure with a deposited gold film layer. Both SPR and MMI effects are excited in a single sensor structure without enlarging the device size. However, at the same time, the interference fringe patterns are also mixed with the SPR transmission spectra, and the traditional SPR interrogation technique becomes unavailable since the resonant wavelength is hard to be located. In this study, the fast Fourier transform and different filtering algorithms are applied, both SPR signal and interference signal with different orders are separated effectively due to their different spatial frequency distributions, and they are processed individually for refractive index (RI) sensing. The experimental results verify that the overall RI sensitivity of the hybrid sensor is significantly enhanced. This study provides an important supplement to the traditional SPR and MMI functions.

One-structure-based multi-effects coupled nanogenerators for flexible and self-powered multi-functional coupled sensor systems

The simultaneous monitoring of multi-physical signals is essential for future sensor systems, but is currently only realized by integrating a variety of sensor types into a single device. However, the ability to use a single sensor structure that shares common electrodes can provide a route to multi-functional sensing while also decreasing device size and increasing spatial resolution. Here we report a ferroelectric barium titanate film-based multi-effect coupled nanogenerator for scavenging light, mechanical, and thermal energies to realize a self-powered multi-functional coupled sensor system without using any external power source. The coupled nanogenerator exhibits a strong coupling enhancement with detection sensitivities of 0.42 nA/(mW/cm2) during illumination by 405 nm light, 1.43 nA/kPa for pressure detection, and −8.85 nA/K for temperature sensing, where both the light and pressure sensing performances have the highest sensitivities during a cooling temperature variation of ~19.5 K and the largest temperature detection sensitivity can be achieved during strong light illumination of 83.2 mW/cm2. Moreover, the coupled nanogenerator array can be integrated into flexible forms for tactile pressure, temperature, and light sensors, and enabling coupled sensing for the development of electronic skins.

Low crosstalk hybrid fiber optic sensor based on surface plasmon resonance and MMI

This Letter proposes a hybrid fiber optic sensor based on surface plasmon resonance (SPR) and multimode interference (MMI). The sensor consists of a single-mode fiber-no-core fiber-single-mode fiber (SMF-NCF-SMF) structure with a partially deposited gold film layer. When compared with the previous studies, the main contribution of this Letter is the introduction of MMI into the SPR sensors; hence, both the SPR and the MMI mechanisms are excited in a single sensor structure for the dual-parameter measurement. The measurement process is realized based on two individual sensing mechanisms and the separated spectral regions (visible or near-infrared); therefore, the crosstalk between the two measured parameters is largely suppressed and has been verified experimentally insignificant. Furthermore, the obvious interference effect can be used to measure a great number of physical parameters; hence, the proposed hybrid fiber optic sensor provides an important supplement to the traditional SPR function.

In situ MEMS gradiometer with nanometer-resolution optical detection system

Mechanically resonant ferromagnetic MEMS sensors intended for magnetic field gradient measurements are presented. Suspended quad-beams with proof mass have been designed to improve their sensitivity and to simplify the detection. Fabricated devices exhibit the compact size of current MEMS technologies and are built within a simple deep-reactive-ion etching-based process. Nanometer-resolution detection based on optical interferometry and signal processing techniques have been employed to find out dynamic-mode transformation factors of 6.25 × 10 −3 T/m/Hz with 0.1-Hz resolution. The device performs in situ gradiometry with a single-sensor structure, which represents a technological advance to current-art gradiometers.

An active tactile sensor for detecting mechanical characteristics of contacted objects

We propose an active tactile sensor actuated by magnetic force. The tactile sensor has the advantage of being able to detect mechanical characteristics related to a tactile impression of contacted objects using a single sensor structure, much as human skin functions. It consists of a displacement-sensing element of piezoresistors formed on a silicon diaphragm, and a magnetic actuating element (a permanent magnet and a flat coil). The sensor has two modes of operation, quasi-static and vibration, and it can detect contact force, elasticity and damping of contacted objects by choosing between operation modes. We fabricated the piezoresistor sensing and magnetic actuating elements by applying the microelectromechanical systems technologies, and assembled them in a hybrid manner. The size of the sensor was 6.0 mm × 6.0 mm × 10 µm. As contact samples we used three different rubber materials with hardness values ranging from A20 to A60 in Shore A. We experimentally confirmed that both the resonance frequency and the Q-factor of the sensing element in the vibration mode changed with different samples. We were able to calculate the elastic and damping coefficients of the contacted rubber objects by analyzing the vibrational response of the diaphragm. From the results, we concluded that the active sensor can detect mechanical characteristics of contacted objects using a single sensor structure.