Elastic particle deformation in rectangular channel flow as a measure of particle stiffness

Transport and Retention Behaviors of Deformable Polyacrylamide Microspheres in Convergent-Divergent Microchannels

Knowledge of the transport and retention behaviors of soft deformable particles on the microscale is essential for the design, evaluation, and application of engineered particle materials in the fields of energy, environment, and sustainability. Emulated convergent-divergent microchannels were constructed and used to investigate the transport and retention behaviors of soft deformable polyacrylamide microspheres at various conditions. Five different types of transport and retention patterns, i.e., surface deposition, smooth passing, direct interception, deforming remigration, and rigid blockage, are observed. Flow resistance variation characteristics caused by different patterns were quantitatively analyzed. Effects of flow rate, pore-throat size, particle size, and injection concentration on transport and retention patterns have been studied, and transport and retention pattern maps are presented and discussed.

Towards the directed evolution of protein materials

Protein-based materials have emerged as a powerful instrument for a new generation of biological materials, with many chemical and mechanical capabilities. Through the manipulation of DNA, researchers can design proteins at the molecular level, engineering a vast array of structural building blocks. However, our capability to rationally design and predict the properties of such materials is limited by the vastness of possible sequence space. Directed evolution has emerged as a powerful tool to improve biological systems through mutation and selection, presenting another avenue to produce novel protein materials. In this prospective review, we discuss the application of directed evolution for protein materials, reviewing current examples and developments that could facilitate the evolution of protein for material applications.

Small asymmetric Brownian objects self-align in nanofluidic channels

Although the self-alignment of asymmetric macro-sized objects of a few tens of microns in size have been studied extensively in experiments and theory, access to much smaller length scales is still hindered by technical challenges. We combine molecular dynamics and stochastic rotation dynamics techniques to investigate the self-orientation phenomenon at different length scales, ranging from the micron to the nano scale by progressively increasing the relative strength of diffusion over convection. To this end, we model an asymmetric dumbbell particle in Hele-Shaw flow and explore a wide range of Péclet numbers (Pe) and different particle shapes, as characterized by the size ratio of the two dumbbell spheres (R[combining tilde]). By independently varying these two parameters we analyse the process of self-orientation and characterize the alignment of the dumbbell with the direction of the fluid flow. We identify three different regimes of strong, weak and no alignment and we map out a state diagram in Pe versus R[combining tilde] plane. Based on these results, we estimate dimensional length scales and flow rates for which these findings would be applicable in experiments. Finally, we find that the characteristic reorientation time of the dumbbell is a monotonically decreasing function of the dumbbell anisotropy.