Dongqing Li

Recent studies on ionic diodes for ion transport regulation have shown promising functions with high rectification ratios. However, typical ionic diodes face challenges in attaining high output efficiency and ion flux due to their requirement of nanoscale dimensions for ion selectivity. In this article, we introduce a novel bipolar ionic diode constructed through the combined assembly of nanoparticles and a transformable polyelectrolyte network. Experimental and numerical studies were conducted to characterize and optimize the fabrication parameters, resulting in a remarkable rectification ratio exceeding 1000. The presented ionic diode possesses the unique capability to automatically transform from a dense to a loose structure in response to an applied potential bias. This feature enables high output efficiency and rapid ion accumulation. Leveraging these characteristics, we developed a fluorescence-based sensor with ultrahigh sensitivity for nickel ions, achieving a detection limit of 1 nM with a minimal sample volume of 50 μL─an improvement of 2 orders of magnitude over conventional bulk solutions with the same fluorescence indicator. This ionic diode demonstrates exceptional ability and flexibility in high-efficiency ion transport, positioning itself as a promising platform with broad applications for enhancing sensitivity in various fluorescence-based sensing applications within aqueous environments.

Most iontronic pressure sensors with planar metallic electrodes exhibit significant performance degradation in the medium to high-pressure range. To achieve high sensitivity in a broad sensing range, compressive porous electrodes (CPE) were employed to fabricate an ultrasensitive hybrid-iontronic pressure sensor. The sensor demonstrates an ultrahigh sensitivity of 198,160 kPa^-1, a pressure resolution of 4.9 Pa, and a broad sensing range extending up to 160 kPa. Notably, the sensor maintains a nearly linear relationship between sensitivity and pressure within the sensing range of 37.5-92.5 kPa. This approach addresses the issue of significantly attenuated sensitivity across a broad pressure range, which arises from the limited thickness variation of planar electrodes. This composite structure, which integrates CPE with ion-loaded PU foam, offers a straightforward, cost-effective, and scalable method for producing ultrasensitive iontronic pressure sensors. The concept demonstration confirmed that CPE-based pressure sensors are capable of sensitively detecting subtle underwater mechanical stimuli, including vibrations and water waves.

Most flexible ionic tactile sensors can hardly be used in deep sea due to their poor antiswelling and anticompression properties under high hydrostatic pressure. To achieve pressure and position sensing under high hydrostatic pressure, a self‐powered underwater tactile sensor made of a porous thermoplastic polyurethane (TPU) film is presented in this paper. The sensor works by generating an electric current due to the different moving velocities of ions in the porous film under pressing. Experimental results show that the magnitude of the generated current signal increases with the applied pressure, the contacting area, and ion concentration of the solution. The direction and magnitude of the current signal depend on the pressing position of the film. The signal magnitude decreased with the closer to the center of the film. The maximum pressure sensitivity and positioning resolution are 0.62 kPa⁻¹ and 1.31 mm respectively. Response time (0.19 s), 0.67 s recovery time, and 50–600 kPa pressure detection range are achieved. In addition, the signal magnitude is decreased only by 15.53% when the sensor is placed underwater at a simulated depth of 100 m. Proof of concept demonstration of underwater autonomously grasping objects of different weights with this sensor is successfully achieved.

This study investigates the surface charging and electrophoretic motion of polyethylene glycol-rich (PEG-rich) micro-droplets in dextran-rich solutions or dextran-rich micro-droplets in PEG-rich solutions.