Nanoparticle-assisted drug delivery has been emerging as an active research area. Understanding and controlling the interaction of the coated-nanoparticles (NPs) with cell membranes is key to the development of the efficient drug delivery technologies and to the management of nanoparticle-related health and safety issues. Cellular uptake of nanoparticles coated with mixed hydrophilic/hydrophobic polymer ligands is known to be strongly influenced by the polymer pattern on the NP surface and remains open for further exploration. To unravel the physical mechanism behind this intriguing phenomenon, here we perform dissipative particle dynamics simulations to analyze the forces and efficacy time as the copolymer-coated NPs pass through the lipid bilayer so as to provide better design of coated-NPs for future drug delivery applications. Four characteristic copolymer ligands are constructed to perform the simulations: hydrophilic-hydrophobic (AB), hydrophobic-hydrophilic (BA), and hydrophobic-hydrophilichydrophobic-hydrophilic (BABA), and a random pattern with hydrophilic and hydrophobic beads. We mainly study the critical force and potential of mean force required for entering inside the lipid bilayer and penetration force to pass all the way through the cell membrane as well as the translocation time for these patterned NPs across the bilayer. Through copolymer ligand pattern designing, we find a suitable nanoparticle candidate with a specific polymer coating pattern for drug delivery. These findings provide useful guidelines for the molecular design of patterned NPs for controllable cell penetrability and help establish qualitative rules for the organization and optimization of copolymers ligands for desired drug delivery.

Thermophoresis has been emerging as a novel technique for manipulating nanoscale particles. Materials with good thermal conductivity and low surface friction, such as graphene, are best suited to serve as a platform for solid-solid transportations or manipulations. Here we employ nonequilibrium molecular dynamics simulations to explore the feasibility of utilizing a thermal gradient on a large graphene substrate to control the motion of a small graphene nanoflake on it. Attempts to systematically investigate the mechanism of graphene-graphene transportation have centered on the fundamental driving mechanism of the motion and the quantitative effect of significant parameters such as temperature gradient and geometry of graphene on the motion of the nanoflake. Simulation results have demonstrated that temperature gradient plays the pivotal role in the evolution of the motion of the nanoflake on the graphene surface. Also, the geometry of nanoflakes has presented an intriguing signature on the motion of the nanoflake, which shows the nanoflakes with a circular shape move slower but rotate faster than other shapes with the identical area. It reveals that edge effects can stabilize the angular motion of thermophoretically driven particles. An interesting relation between the effective initial driving force and temperature gradient has been quantitatively captured by employing the steered molecular dynamics. These findings will provide fundamental insights into the motion of nanodevices on a solid surface due to thermophoresis, and will offer the novel view for manipulating nanoscale particles on a solid surface in techniques such as cell separation, water purification, and chemical extraction.

The recent capability of synthesizing large-scale crumpled graphene-related 2D materials has motivated intensive efforts to boost its promising applications in electronics, energy storage, composites and biomedicine. As deformation of graphene-related 2D materials can strongly affect their properties and the performance of graphene-based devices and materials, it is highly desirable to attain subtle control of reversible wrinkling and crumpling of graphene. Graphyne, a 2D lattice of sp(2)- and sp(1)-hybridized carbons similar to graphene, has remained unexplored with respect to its crumpling behavior. Here we employ molecular dynamics simulation to explore the behavior of graphynes under geometric confinement across various temperatures, sizes, and crumpling rates and compare them to graphene under the same conditions, with a focus on the mechanical stabilizing mechanisms and properties of the crumpled structures. The lower density of graphynes creates less deformation-induced bending energy than graphene; as such the graphynes exhibit a markedly increased propensity for stable crumpling. It is also shown that the crumpled 2D carbon materials demonstrate the hardness and bulk modulus of an equivalent magnitude with crumpled graphene, with the most important behavior-determining factor being the number of linking sp(1)-hybridized carbons in the material. Our results show that irrespective of the initial geometry and crumpling rate, the final structures present intriguing and useful properties which can be incorporated into crumpled graphene structures.

Nanoporous silicon has been emerging as a powerful building block for next-generation sensors, catalysts, transistors, and tissue scaffolds. The capability to design novel devices with desired mechanical properties is paramount to their reliability and serviceability. In order to bring further resolution to the highly variable mechanical characteristics of nanoporous silicon, here we perform molecular dynamics simulations to study the effects of ligament thickness, relative density, and pore geometry/orientation on the mechanical properties of nanoporous silicon, thereby determining its Young's modulus, ultimate strength, and toughness as well as the scaling laws versus the features of interior ligaments. Results show that pore shape and pattern dictate stress accumulation inside the designed structure, leading to the corresponding failure signature, such as stretching-dominated, bending-dominated, or stochastic failure signatures, in nanoporous silicon. The nanostructure of the material is also seen to drive or mute size effects such as "smaller is stronger" and "smaller is ductile". This investigation provides useful insight into the behavior of nanoporous silicon and how one might leverage its promising applications.