One Droplet toward Efficient Alcohol Detection Using Femtosecond Laser Textured Micro/Nanostructured Surface with Superwettability

Femtosecond laser composite manufactured double-bionic micro-nano structure for efficient photothermal anti-icing/deicing

The solar anti-icing/deicing (SADI) strategy represents an environmentally friendly approach for removing ice efficiently. However, the extensive use of photothermal materials could negatively impact financial performance. Therefore, enhancing light utilization efficiency, especially by optimizing the design of a structure with a low content of photothermal materials, has rapidly become a focal point of research. Drawing inspiration from the antireflective micro-nano structure of compound eyes and the thermal insulating hollow structure of polar bear hair, we proposed a new strategy to design a bionic micro-nano hollow film (MNHF). The MNHF was created using a composite manufacturing process that combines femtosecond laser ablation with template transfer techniques. Both theoretical simulations and empirical tests have confirmed that this structure significantly improves photothermal conversion efficiency and thermal radiation capability. Compared to plane film, the photothermal conversion efficiency of MNHF is increased by 45.85%. Under 1.5 sun, the equilibrium temperature of MNHF can reach 73.8 °C. Moreover, even after 10 icing-deicing cycles, MNHF maintains an ultra-low ice adhesion strength of 1.8 ± 0.3 kPa. Additionally, the exceptional mechanical stability, chemical resistance, and self-cleaning capabilities of the MNHF make its practical application feasible. This innovative structure paves the way for designing cost-effective and robust surfaces for efficient photothermal anti-icing/deicing on airplane wings.

Photothermal Conversion of the Oleophilic PVDF/Ti3C2Tx Porous Foam Enables Non-Aqueous Liquid System Applicable Actuator

Various physical and chemical reaction processes occur in non-aqueous liquid systems, particularly in oil phase systems. Therefore, achieving efficient, accurate, controllable, and cost-effective movement and transfer of substances in the oil phase is crucial. Liquid-phase photothermal actuators (LPAs) are commonly used for material transport in liquid-phase systems due to their remote operability and precise control. However, existing LPAs typically rely on materials like hydrogels and flexible polymers, commonly unsuitable for non-aqueous liquids. Herein, a 3D porous poly(vinylidene fluoride) (PVDF)/Ti3C2Tx actuator is developed using a solvent displacement method. It demonstrates directional movement and controlled material transport in non-aqueous liquid systems. When subject to infrared light irradiation (2.0 W cm-2), the actuator achieves motion velocities of 7.3 and 6 mm s-1 vertically and horizontally, respectively. The actuator's controllable motion capability is primarily attributed to the foam's oil-wettable properties, 3D porous oil transport network, and the excellent photothermal conversion performance of Ti3C2Tx, facilitating thermal diffusion and the Marangoni effect. Apart from multidimensional directions, the actuator enables material delivery and obstacle avoidance by transporting and releasing target objects to a predetermined position. Hence, the developed controllable actuator offers a viable solution for effective motion control and material handling in non-aqueous liquid environments.

Controllable Fabrication of Hydrophilic Surface Micro/Nanostructures of CFRP by Femtosecond Laser

Carbon fiber reinforced polymer (CFRP), a highly engineered lightweight material with superior properties, is widely used in industrial fields, such as aerospace, automobile, and railway transportation, as well as medical implants and supercapacitor. This work presents an effective surface treatment method for the controllable fabrication of hydrophilic surface micro/nanostructures of CFRP through femtosecond laser processing. Selective removal of the epoxy resin and leaving the carbon fibers exposed are achieved when CFRP is weakly ablated by a femtosecond laser. The diameters and structures of the carbon fibers can be controlled by adjusting the laser processing parameters. Three-dimensional surface micro/nanostructures are processed when CFRP is strongly ablated by a femtosecond laser. Meanwhile, the transformation of the sp2 orbitals to sp3 orbitals of graphitic carbons of carbon fibers is induced by a femtosecond laser. Moreover, the investigation of surface roughness and wettability of femtosecond laser-processed CFRP indicates increased roughness and excellent hydrophilicity (a contact angle of 28.1°). This work reveals the effect of femtosecond laser processing on the regulation of the physicochemical properties of CFRP, which can be applicable to surface treatment and performance control of other fiber-resin composites. The excellent hydrophilicity will be conducive to the combination of CFRP with other materials or to reducing the friction resistance of CFRP used in medical implants.

Advanced Fog Harvesting Method by Coupling Plasma and Micro/Nano Materials

Harvesting fog is a potential and effective way to alleviate the crisis of water resource shortage. A highly efficient and economical fog harvesting method has always been a global and common goal. Here, a promising fog harvesting method by coupling plasma and micro/nano materials is proposed, which can achieve 93% fog collection efficiency with consuming power of only 0.76 W/0.04 m2. The basic method is to utilize nanoparticles to decorate both the discharge electrode and the collecting electrode of the micro/nano electrostatic fog collector. For the discharge electrode, the nanoparticles can achieve an order of magnitude higher electric field strength and a 28.6% decrease in the operating voltage (14 kV decreases to 10 kV). For the collecting electrode, a novel composite structure of hydrophobic/hydrophilic (HB/HL) is proposed. The core advantage is the directional droplet transport at the junction of HB and HL caused by surface tension can adjust the accumulated droplets on the two sides, which avoids the droplet residue and mesh blockage in the general structure. This technology provides an innovative approach for the collection of microdroplets and a new design idea for the fog collector to deal with the water crisis.

Bioinspired Flexible Wearable Sensor with High Self-Cleaning and Antibacterial Performance for Human Motion Sensing

Flexible wearable strain sensors have shown great potential in monitoring human motion, due to their ability to flexibly fit to multiple surfaces, which can realize the monitoring of human motions and external stimulation. However, the utilization of the sensor in extreme conditions such as low or high temperatures still poses a risk of signal output distortion. Moreover, the continuous usage of the sensor may result in extensive bacterial growth at the interface between the sensor and the skin, posing a threat to human health. Herein, a hydrophobic flexible antibacterial strain sensor (CGP) based on carbon black-PDMS was prepared, inspired by the superhydrophobic surface of a lotus leaf. The CGP sensor demonstrates exceptional sensitivity, with a gauge factor (GF) of 0.467 in the strain range of 0-15% and a fast response time (65.4 ms, 5% strain). Additionally, it exhibits a high conductivity of 1.2 mS cm-1 at -20 °C and 2.0 mS cm-1 at 100 °C, indicating its ability to function effectively even in extreme temperatures. The static water contact angle of CGP measures 121.7°, and self-cleaning experiments have confirmed its excellent self-cleaning performance. Furthermore, the CGP displays distinct response characteristics to movements of human fingers, wrists, and knees, making it an ideal choice for monitoring various joints in the human body. In terms of antibacterial properties, CGP has demonstrated an antibacterial rate of over 99% against E. coli and S. aureus. Possessing high sensitivity, superior electrical conductivity in harsh environments, and super antibacterial capabilities, CGP holds significant potential for applications in human motion monitoring and other fields.