The transport of particles across lipid-bilayer membranes is important for biological cells to exchange information and material with their environment. Large particles often get wrapped by membranes, a process which has been intensively investigated in the case of hard particles. However, many particles in vivo and in vitro are deformable, e.g., vesicles, filamentous viruses, macromolecular condensates, polymer-grafted nanoparticles, and microgels. Vesicles may serve as a generic model system for deformable particles. Here, we study nonspherical vesicles with various sizes, shapes, and elastic properties at initially planar lipid-bilayer membranes. Using the Helfrich Hamiltonian, triangulated membranes, and energy minimization, we predict the interplay of vesicle shapes and wrapping states. Increasing particle softness enhances the stability of shallow-wrapped and deep-wrapped states over nonwrapped and complete-wrapped states. The free membrane mediates an interaction between partial-wrapped vesicles. For the pair interaction between deep-wrapped vesicles, we predict repulsion. For shallow-wrapped vesicles, we predict attraction for tip-to-tip orientation and repulsion for side-by-side orientation. Our predictions may guide the design and fabrication of deformable particles for efficient use in medical applications, such as targeted drug delivery.

This article introduces the concept of Impact Printing, a new additive manufacturing (AM) method that aggregates malleable discrete elements (or soft particles) by a robotic shooting process. The bonding between the soft particles stems from the transformation of kinetic energy, gained during the acceleration phase, into plastic deformation upon impact. Hence, no additional binding material is needed between the soft particles; the cohesion and self-interlocking capacities of the material itself acts as the primary binding agent. Shooting, and consequent impacting, forces can be modulated and result in distinct compaction ratios. By linearly shooting material, we decouple the deposition apparatus from the produced parts and provide flexibility to the deposition process to potentially build in any directions or onto uncontrolled surfaces. Impact Printing produces parts with formal characteristics standing between brick laying-assembly of discrete building blocks-and 3D Printing-computer-controlled depositioning or solidifying of material. It brings forward a novel digital fabrication method and an alternative to the conventional continuous AM process. This article validates the Impact Printing approach with a series of prototypical experiments, conducted with a robotic fabrication setup consisting of a six-axis robotic arm mounted with a material shooting apparatus, that forms, orients, and projects the soft particles. We will explain and demonstrate its principles and define the fabrication parameters, such as shooting force, shooting distance, and the resulting aggregations\' characteristics.

With the increasing global demand for clean-label and sustainable emulsifiers that are suitable for use in agrochemicals, personal care and food industry, protein-based particles are becoming promising emulsion stabilizer in food industry owing to their considerable surface activity, biodegradability and excellent nutritional value. Accumulating evidence implies that, relative to classical rigid inorganic particles, protein colloidal particles perform more as soft particles to stabilize emulsions. A brief historical introduction to Pickering emulsions provides a conceptual framework firstly. Then, the conformational properties and methods of fabrication and modification of protein-based particles are introduced in more detail. In addition, the particle shape, interfacial arrangement and interaction are also discussed. Finally, novel application of these materials and future perspectives concerning the interfacial conformation, rheology and industrial production of protein-based Pickering particles are considered. In summary, thermal and solvent-induced aggregation are found to be the principal fabrication methods of protein-based Pickering particles. Through the complexation or covalent interaction with polysaccharides, proteins and phenolics, protein particles exhibit improved solubility, emulsification effectiveness and bioactive functionalities. According to different shapes, protein-based Pickering particles can be categorized into elongated and linear particles, spherical particles, plate-shaped particles, and fractal aggregates, which have different interfacial adsorption energy. Overall, the embedding arrangement, interfacial rheology and large-scale production of protein particles are challenges as well as opportunities that coexist in further studies.

Interest in the electrical properties of the interface between soft (or polymer-grafted) nanoparticles and solutions is considerable. Of particular significance is the case of polyelectrolyte-coated particles, mainly taking into account that the layer-by-layer procedure allows the control of the thickness and permeability of the layer, and the overall charge of the coated particle. Like in simpler systems, electrokinetic determinations in AC fields (including dielectric dispersion in the 1 kHz-1 MHz frequency range and dynamic electrophoresis by electroacoustic methods in the 1-18 MHz range) provide a large amount of information about the physics of the interface. Different models have dealt with the electrokinetics of particles coated by a single polymer layer, but studies regarding multi-layered particles are far scarcer. This is even more significant in the case of so-called salt-free systems; ideally, the only charges existing in this case consist of the charge in the layer(s) and the core particle itself, and their corresponding countercharges, with no other ions added. The aims of this paper are as follows: (i) the elaboration of a model for the evaluation of the electrokinetics of multi-grafted polymer particles in the presence of alternating electric fields, in dispersion media where no salts are added; (ii) to carry out an experimental evaluation of the frequency dependence of the dynamic (or AC) electrophoretic mobility and the dielectric permittivity of suspensions of polystyrene latex spherical particles coated with successive layers of cationic, anionic, and neutral polymers; and (iii) finally, to perform a comparison between predictions and experimental results, so that it can be demonstrated that the electrokinetic analysis is a useful tool for the in situ characterization of multilayered particles.

The intercalation strategy is successfully applied in tuning the interlayer distance of 2D membranes for efficient desalination and ion sieving. However, it is difficult to pursue a intercalant that is few nanometers in size and suitable for further chemical modification . Here, for the first time, we report the intercalation of soft particles-polyacrylonitrile gel particles (PAN GPs) inside the graphene oxide (GO) membranes, which allows for a tunable interlayer distance via the deformation of soft particles. Furthermore, the base-induced hydrophobic/hydrophilic structure of PAN GPs facilitates the water diffusion through the GO membrane. A fast and selective water permeation was observed through separation Cu-EDTA2-from water, with the permeance of 4-13 times higher than the reported 2D membranes. Intercalation of soft particles represents a promising strategy to fabricate high-performance 2D membranes.

Within the framework of analytical theories for soft surface electrophoresis, soft particles are classically defined by a hard impermeable core of given surface charge density surrounded by a polyelectrolyte shell layer permeable to both electroosmotic flow and ions from background electrolyte. This definition excludes practical core-shell particles, e.g. dendrimers, viruses or multi-layered polymeric particles, defined by a polyelectrolytic core where structural charges are distributed and where counter-ions concentration and electroosmotic flow velocity can be significant. Whereas a number of important approximate expressions has been derived for the electrophoretic mobility of hard and soft particles, none of them is applicable to such generic composite core-shell particles with differentiated ions- and fluid flow-permeabilities of their core and shell components. In this work, we elaborate an original closed-form electrophoretic mobility expression for this generic composite particle type within the Debye-Hückel electrostatic framework and thin double layer approximation. The expression explicitly involves the screening Debye layer thickness and the Brinkman core and shell hydrodynamic length scales, which favors so-far missing analysis of the respective core and shell contributions to overall particle mobility. Limits of this expression successfully reproduce results from Ohshima\'s electrophoresis theory solely applicable to soft particles with or without hard core.

In this article, we review the applications of a novel theory (Ohshima 2009 Sci. Technol. Adv. Mater.10 063001) to the analysis of electrokinetic data for various soft particles, that is, particles covered with an ion-permeable surface layer of polyelectrolytes. Soft particles discussed in this review include various biological cells and hydrogel-coated particles as a model of biological cells. Cellular transformations increase the concentration of sialic acid of glycoproteins and are associated with blocked biosynthesis of glycolipids and aberrant expression of the developmentally programmed biosynthetic pathway. The change in shape or biological function of cells may affect their surface properties and can be detected by electrokinetic measurements. The experimental results were analyzed with Ohshima\'s electrokinetic formula for soft particles and soft surfaces. As a model system, hydrogel surfaces that mimic biological surfaces were also prepared and their surface properties were studied.

The electrokinetic properties of carboxymethyldextran, a soft and anionic polysaccharide, were analysed in aqueous NaNO3 solutions through measurements of the electrical conductivity of the suspensions. The results, which furnish new experimental support for the structure of soft polysaccharides in electrolyte solution show that the polyion concentration governs the conductance behavior of the suspension as the ionic strength decreases. This is particularly evident for large polymer concentrations, for which electrical double layer overlap is more likely. In contrast, the electrical conductivity of the suspension at high ionic strength reduces to the contribution of the ions in solution, as screening of the polyion charges is more efficient in such conditions. The applicability of Ohshima\'s general conductivity expression to these electrical conductivity measurements was examined, and a major discrepancy against the theory was observed. The calculated values of the electrical conductivity deduced on the basis of this theory were found to be lower than the experimental ones. Possible reasons for this discrepancy are discussed and a numerical model, based on the use of a cell approach to account for hydrodynamic and electrical interactions between particles, has shown to be a good description of the experimental electrokinetic data.

The engineering of defects in crystalline matter has been extensively exploited to modify the mechanical and electrical properties of many materials. Recent experiments on manipulating extended defects in graphene, for example, show that defects direct the flow of electric charges. The fascinating possibilities offered by defects in two dimensions, known as topological defects, to control material properties provide great motivation to perform fundamental investigations to uncover their role in various systems. Previous studies mostly focus on topological defects in 2D crystals on curved surfaces. On flat geometries, topological defects can be introduced via density inhomogeneities. We investigate here topological defects due to size polydispersity on flat surfaces. Size polydispersity is usually an inevitable feature of a large variety of systems. In this work, simulations show well-organized induced topological defects around an impurity particle of a wrong size. These patterns are not found in systems of identical particles. Our work demonstrates that in polydispersed systems topological defects play the role of restoring order. The simulations show a perfect hexagonal lattice beyond a small defective region around the impurity particle. Elasticity theory has demonstrated an analogy between the elementary topological defects named disclinations to electric charges by associating a charge to a disclination, whose sign depends on the number of its nearest neighbors. Size polydispersity is shown numerically here to be an essential ingredient to understand short-range attractions between like-charge disclinations. Our study suggests that size polydispersity has a promising potential to engineer defects in various systems including nanoparticles and colloidal crystals.