It is highly challenging to construct a durable superhydrophobic coating for practical applications since the coating is easily destroyed by mechano-chemical attack. To address this issue, a “PDMS-in-water” emulsion approach is for the first time adopted to design a mechanochemically robust superhydrophobic cotton fabric with intelligent self-healing nature, without using any fluorine-containing components. With this approach, PDMS molecules firstly penetrate into the cotton fiber, and then graft onto the surface of the cotton fabric with a strong binding force, creating hierarchical rough structures and lowering the surface energy simultaneously. Benefitting from this design, the PDMS@cotton fabric exhibits high superhydrophobicity with a water contact angle over 155°, surpassing all the PDMS-in-organic solvent based approaches. Impressively, the surface repairs its superhydrophobicity throughout the whole lifetime though damaged by machine washing or abrasion (>100 cycles), due to the self-diffusion process of PDMS molecules from the inner part to the outer surface of the cotton fibers to minimize surface free energy. Besides, the superhydrophobic coatings display superior chemical stability in strongly acidic and alkaline solution, and maintain similar textile physical properties of the cotton fabric, such as elongation at break, tensile strength, etc. Our environment-friendly “PDMS-in-water” approach can be easily integrated into industrial textile finishing treatment and is promising to apply to various substrates with robust superhydrophobic surfaces.

Flexible actuation of droplets is crucial for biomedical and industrial applications. Hence, various approaches using optical, electrical, and magnetic forces have been exploited to actuate droplets. For broad applicability, an ideal approach should be programmable and be able to actuate droplets of arbitrary size and composition. Here we present an “additive-free” magnetic actuation method to programmably manipulate droplets of water, organic, and biological fluids of arbitrary composition, as well as solid samples, on a ferrofluid-infused porous surface. We specifically exploit the spontaneously formed ferrofluid wetting ridges to actuate droplets using spatially varying magnetic fields. We demonstrate programmed processing and analysis of biological samples in individual drops as well as the collective actuation of large ensembles of micrometer-sized droplets. Such model respiratory droplets can be accumulated for improved quantitative and sensitive bioanalysis - an otherwise prohibitively difficult task that may be useful in tracking coronavirus.

The cracking and iridescence properties of photonic crystals (PCs) greatly limit their availability, especially in the realms of color displays and optical devices. Herein, crack-free amorphous PCs with enhanced color contrast and low angle dependence were fabricated by the co-assembly of polydopamine-coated polystyrene core–shell nanoparticles (PS@PDA NPs) and 3-aminopropyltriethoxysilane (APTES) via a thermal-assisted self-assembly method. The covalent bonds, generated from Schiff base reaction or Michael addition between polydopamine (PDA) and APTES, successfully counteract the tensile stress that is initiated from latex shrinkage during drying, thereby enabling the formation of crack-free PCs. Moreover, thanks to the light-absorbing nature of PDA, a mussel-inspired melanin, and the amorphous arrays, these as-prepared crack-free PCs miraculously exhibit high visibility and low angle dependent structural colors. This facile, low-cost and environmentally friendly approach for preparing crack-free amorphous PCs can be employed in diverse colloidal sphere systems and may boost the promising applications of PCs.