A proteinaceous superhydrophobic material for facile protein crystallization is reported. The lysozyme phase transition is rationally manipulated to form a reliable superhydrophobic coating on virtually arbitrary material surfaces with good thermostability and mechanical robustness. Such a surface exhibits a fascinating capability to drive protein crystallization, and the protein crystal array can be facilitated in a large area at an ultralow protein concentration.

Controlling the droplet evaporation on surfaces is desired to get uniform depositions of materials in many applications, for example, in two- and three-dimensional printing and biosensors. To explore a new route to control droplet evaporation on surfaces and produce asymmetric particles, sessile droplets of aqueous dispersions were allowed to evaporate from surfaces coated with oil films. Here, we applied 1–50 μm thick films of different silicone oils. Two contact lines were observed during droplet evaporation: an apparent liquid–liquid–air contact line and liquid–liquid–solid contact line. Because of the oil meniscus covering part of the rim of the drop, evaporation at the periphery is suppressed. Consequently, the droplet evaporates mainly in the central region of the liquid–air interface rather than at the droplet’s edge. Colloidal particles migrate with the generated upward flow inside the droplet and are captured by the receding liquid–air interface. A uniform deposition ultimately forms on the substrate. With this straightforward approach, asymmetric supraparticles have been successfully fabricated independent of particle species.

Self-assembled monolayers (SAMs) have been widely employed as etching resists in wet lithography systems to form patterns in which the ordered molecular packing of the SAM regions significantly delays the etchant attack. A generally accepted recognition is that the SAMs ability to resist etching is positively correlated to the quality of the surface-assembled structures, and a more ordered molecular packing would correspond to a better etching resistance. Such a classical belief is debated in the present work by providing an alternative SAM-assisted negative lithography where ordered SAM regions are etched more quickly than their disordered counterparts. This method features a unique photoirradiation-imprinted patterning process that simply consists of two steps: (1) UV irradiation on an OH-terminated SAM-modified gold surface through a photomask and (2) the subsequent immersion of the exposed substrate in an aqueous etching solution of N-bromosuccinimide/pyridine to develop a wet lithographic pattern. The entire experimental process reveals a finding from previous work that the etching rate on the UV-exposed regions with disordered molecular packing could be modulated to be slower than that in the unexposed well-defined SAM regions. Longer irradiation times would also revert the patterns from negative to positive. Thus, by merely using one kind of SAM-modified surface to provide both positive and negative micropatterns on gold layers, one could obtain flexible opportunities for high-resolution micro/nanofabrication resembling photolithography.

The control of liquid motion on the micrometer scale is important for many liquid transport and biomedical applications. An efficient way to trigger liquid motion is by introducing surface tension gradients on free liquid interfaces leading to the Marangoni effect. However, a pronounced Marangoni-driven flow generally only occurs at a liquid–air or liquid–liquid interface but not at solid–liquid interfaces. Using superhydrophobic surfaces, the liquid phase stays in the Cassie state (where liquid is only in contact with the tips of the rough surface structure and air is enclosed in the indentations of the roughness) and hence provides the necessary liquid–air interface to trigger evident Marangoni flows. We use light to asymmetrically heat this interface and thereby control liquid motion near superhydrophobic surfaces. By laser scanning confocal microscopy, we determine the velocity distribution evolving through optical excitation. We show that Marangoni flow can be induced optically at structured, air-entrapping superhydrophobic surfaces. Furthermore, by comparison with numerical modeling, we demonstrate that in addition to the Marangoni flow, buoyancy-driven flow occurs. This effect has so far been neglected in similar approaches and models of thermocapillary driven flow at superhydrophobic surfaces. Our work yields insight into the physics of Marangoni flow and can help in designing new contactless, light-driven liquid transport systems, e.g., for liquid pumping or in microfluidic devices.

Based on a concept of a smooth and steady landing of fragile objects without destruction via a soft cushion, we have developed a model for the soft landing of deformable lipid giant unilamellar vesicles (GUVs) on solid surfaces. The foundation for a successful soft landing is a solid substrate with a two-layer coating, including a bottom layer of positively charged lysozymes and an upper lipid membrane layer. We came to a clear conclusion that anionic GUVs when sedimented on a surface, the vesicle rupture occurs upon the direct contact with the positively charged lysozyme layer due to the strong coulombic interactions. In contrast, certain separation distances was achieved by the insertion of a soft lipid membrane cushion between the charged GUVs and the lysozyme layer, which attenuated the coulombic force and created a mild buffer zone, ensuring the robust capture of GUVs on the substrate without their rupture. The non-covalent bonding facilitated a fully reversible stimuli-responsive capture/release of GUVs from the biomimetic solid surface, which has never been demonstrated before due to the extreme fragility of GUVs. Moreover, the controllable capture/release of cells has been proven to be of vital importance in biotechnology, and similarity the present approach to capture/release cells is expected to open the previously inaccessible avenues of research.