Micropatterning of Highly Stretchable Tough Polymer Actuators for Multistage Detection of Acetone Vapors

Magnetic field-assisted fabrication of quasi-bilayered, multi-responsive and patternable actuators

Quasi-bilayered actuators composed of Fe3O4-decorated graphene oxide and polyvinylidene fluoride have been fabricated in a magnetic field. The actuators could stably respond to multiple stimuli including infrared light, acetone vapour and a magnetic field. The actuator is also patternable because of the magnetism-induced spatial distribution of fillers in the matrix.

Alkyne-to-alkene conversion in graphdiyne driving instant reversible deformation of whole carbon film

The emerging field of soft robotics demands the core actuators and related responsive functional materials with rapid responsiveness and controllable accurate deformation. Here, we developed an alkyne-to-alkene chemical bond conversion way as the driving force to control ultrasensitive and instant reversible deformation of 2D carbon graphdiyne (GDY) film with an asymmetric interface design. The alkyne-to-alkene chemical bond conversion was triggered by acetone through the fast binding and release process. The as-fabricated GDY-based deformation modulator was exhibited to rapidly change shape (within 0.15 seconds) while dipped in an acetone vapor atmosphere and recover to its original form when exposed to air (recovery time < 0.01 seconds), with outstanding properties like large curvature, quick recovery time, excellent stability, and repeatability. It could mimic the movement of mosquito larvae, displaying great promise as micro bionic soft robots. Our results suggest alkyne-to-alkene bond conversion as a unique driving force for developing smart materials for areas like intelligent robotics and bionics.

Light Stimuli-Responsive Superhydrophobic Films for Electric Switches and Water-Droplet Manipulation

Fabrication of superhydrophobic films with large and sensitive deformed actuations driven by light stimuli for the emerging application fields such as biomimetic devices, artificial muscles, soft robotics, electric switches, and water-droplet manipulation remains challenging. Herein, a facile strategy is proposed to fabricate a light stimuli-responsive superhydrophobic film (LSSF) by integrating a bottom carbon nanotube/poly(vinylidene fluoride) (CNT/PVDF) layer, a middle chitosan (CS) layer, and a top superhydrophobic fumed silica-chitosan (SiO₂/CS) layer modified with 1H,1H,2H,2H-heptafluorodecyltrimethoxysilane (FAS). Under near-infrared (NIR) light irradiation, the LSSF quickly bent toward the CS layer with a large bending angle (>200°), high sensitivity (∼7 °C change), and great repeatability (>1000 cycles), which was attributed to the significant difference in the coefficient of thermal expansion (CTE) between CS and PVDF and the water desorption-induced volume shrinking in the CS layer. Furthermore, the LSSF also exhibited superhydrophobicity with a high water contact angle of 165° and a low water sliding angle of 2.8°. Importantly, owing to the high light absorption of CNTs, the LSSF-based biomimetic flower was able to not only bloom under NIR light exposure but also normally work when applying sunlight irradiation. Thanks to the electric conductivity and excellent water repellency, the LSSF was capable of being designed as an electric switch to remotely turn on/off the circuit even under a watery environment, and the LSSF was further successfully applied in water-droplet manipulation. The findings conceivably provided a new strategy to fabricate light stimuli-responsive superhydrophobic films for versatile applications.

Nanoscale Effect of Zirconia Filler Surface on Mechanical Tensile Strength of Polymer Composites

A characteristic effect of a nano-concave-convex structure of a zirconia nanoparticle assembly with an inherent porous structure and huge surface area enabled us to introduce systematic surface modification by thermal treatment to smooth surface and polymer impregnation to mask the nano-concave-convex structure of the zirconia nanoparticle assembly. A polymer composite prepared from 30 wt% poly(N-isopropylacrylamide) containing 0.02 wt% zirconia nanoparticle assembly with the inherent nano-concave-convex surface structure showed the highest tensile strength in mechanical tensile testing. However, both sintered zirconia nanoparticle assembly with smooth surface and zirconia nanoparticle assemblies with polymer masked surface showed lower strength with longer elongation at break in mechanical tensile testing.

Photocrosslinking Patterning of Single-Layered Polymer Actuators for Controllable Motility and Automatic Devices

Shape-programmed deformation of soft polymer films is essential for applications in robotics, self-adaptive devices, and sensors. In comparison to bilayer polymer actuators, the challenge remains to manipulate single-layered soft actuators for rapid, reversible, and shape-programmed deformations in response to external stimuli owing to their homogeneous composite structures. Herein, this work reports a soft polymer film actuator that has a single-layered structure, yet demonstrates the shape-programmed motility. The actuator is composed of polyvinylidene fluoride film as a matrix and patterned by photocrosslinking of acrylamide and N', N'-methylenebisacrylamide, which generates soft-hard alternating segments in the structure. As it is exposed to acetone vapors, the soft-hard structures lead to an unequal response that results in the shape-programmed deformation. The actuator is elastic (strain: 160%) and tough (stress: 40 MPa) and can maintain its rapid, reversible, and shape-programmed motions for a few hours, even longer. The soft-hard structure enables the film actuator (3.5 mg) to give a contracting stress of 4 MPa that is used in an automatic device able to lift a cargo of 5.09 g, ∼1453 times heavier than the film itself. The power output reaches 474 J kg^-1, ∼100 times higher than the reported soft actuators. This simple application indicates a potential for the soft actuator used in acetone vapor sensing devices.

Pre-patterning and post-oxidation-crosslinking of Fe(0) particles for a humidity-sensing actuator

The combination of physical pre-patterning and chemical post-crosslinking strategies enables a humidity-sensing actuator with differential mechanical tensors for controlled interfacial sensitivity.