Single-material solvent-sensitive fluorescent actuator from carbon dots inverse opals based on gradient dewetting

Photochromic Azobenzene Inverse Opal Film toward Dynamic Anti-Fake Pattern

Azobenzene mesogens have garnered considerable research attention in the realm of photo-responsive materials due to their reversible trans-cis isomerization. In this paper, we demonstrate an azobenzene inverse opal film synthesized via photo-polymerization from a SiO2 opal template. The proposed design exhibits intriguing optical properties, including dynamic fluorescent features, distinct fluorescent enhancement, and an anti-fake micropattern with a switchable structure color. This work holds significant importance for advancing the development of novel optical devices.

Solvent Sorption-Induced Actuation of Composites Based on a Polymer of Intrinsic Microporosity

Materials that are capable of actuation in response to a variety of external stimuli are of significant interest for applications in sensors, soft robotics, and biomedical devices. Here, we present a class of actuators using composites based on a polymer of intrinsic microporosity (PIM). By adding an activated carbon (AX21) filler to a PIM, the composite exhibits repeatable actuation upon solvent evaporation and wetting and it is possible to achieve highly controlled three-dimensional actuation. Curled composite actuators are shown to open upon exposure to a solvent and close as a result of solvent evaporation. The degree of curling and actuation is controlled by adjusting the amount of filler and evaporation rate of the solvent casting process, while the actuation speed is controlled by adjusting the type of solvent. The range of forces and actuation speed produced by the composite is demonstrated using acetone, ethanol, and dimethyl sulfoxide as the solvent. The maximum contractile stress produced upon solvent desorption in the pure PIM polymer reached 12 MPa, with an ultimate force over 20 000 times the weight of a sample. This form of the composite actuator is insensitive to humidity and water, which makes it applicable in an aqueous environment, and can survive a wide range of temperatures. These characteristics make it a promising actuator for the diverse range of operating conditions in robotic and medical applications. The mechanism of actuation is discussed, which is based on the asymmetric distribution of the carbon filler particles that leads to a bilayer structure and the individual layers expand and contract differently in response to solvent wetting and evaporation, respectively. Finally, we demonstrate the application of the actuator as a potential drug delivery vehicle, with capacity for encapsulating two kinds of drugs and reduced drug leakage in comparison to existing technologies.

Lyophilic but Nonwettable Organosilane-Polymerized Carbon Dots Inverse Opals with Closed-Cell Structure

This paper presents a unique lyophilic but nonwettable property of organosilane-polymerized carbon dots inverse opals photonic crystals (SiCDPCs) with closed-cell structure. Little stopband shift was observed for the SiCDPCs when being immersed into the solvents such as isopropanol, olive oil, DMSO, hexane, silicone oil, ethanediol, etc. but keeping lyophilic property. This could be attributed to the combined effect of closed-cell structure and the unique chemical composition of SiCDPCs. Furthermore, more than 30 kinds of organic solvents had been investigated, it was found that there were two kinds of factors that affected the stopband shift upon solvent's immersing; one was the polarity of solvent, and the other one was the viscosity of solvent. That is, mainly nonpolar or high viscosity solvents showed lyophilic but nonwettable property. The distinct solvent-responsive behaviors of the SiCDPCs toward polar/nonpolar solvents had been utilized for the fabrication of 2D/3D pattern. Additionally, the as-prepared SiCDPCs showed improved optical limiting property, excellent low-temperature resistance, and abrasion tolerant property. It is of great importance for the development of multifunctional novel coating materials and creation of novel optical devices.