Polymers and Composite Materials

This text serves to cover in more detail polymer physics concepts and specifically how polymers respond from the atomistic to meter length scale. This text spans topics from polymerization chemistry, chain models, Flory-Huggins theory, viscosity, characterization techniques, self assembly, polymer dynamics, viscoelasticity, and mechanics of polymer and composite materials. This work is licensed under a Creative Commons Attribution-NonCommerical-No Derivative Works 4.0 License.https://scholarlycommons.pacific.edu/open-textbooks/1017/thumbnail.jp

Mechanical Behavior of Materials

This text serves to cover in more detail solid mechanics concepts and specifically the material response to stress and strain. This text spans solid mechanics concepts from stress and strain at an atomistic length scale, to linear elasticity, anisotropy, linear viscoelasticity, plasticity, dislocation generation and interactions, and fracture.https://scholarlycommons.pacific.edu/open-textbooks/1015/thumbnail.jp

Materials Science and Engineering

This text serves to provide a brief overview of some of the myriad of topics available for study in the field of Materials Science. This is by no means a comprehensive compilation of Materials Science and Engineering topics but is instead meant as an introduction to the topic for entry-level undergraduates who want to pursue a career studying materials.https://scholarlycommons.pacific.edu/open-textbooks/1007/thumbnail.jp

Systems and method for viral detection

Systems and methods are provided for detecting viral particles, viral proteins, viral RNA, or viral DNA in multiple fluids. The methods consist of applying a magnetic torque to functionalized magnetic beads in a fluid solution resting on a functionalized substrate. The solution is comprised of one of the following: intact viral particles, viral proteins, RNA, or DNA. The presence and/or quantity of the aforementioned molecules or viruses is detected by measuring the translational velocity of the beads. The methods here described can detect multiple different species simultaneously using a multiplexed assay. Also, the systems here included are able to process multiple samples simultaneously

Aggregation dynamics of active rotating particles in dense passive media

Active matter systems are able to exhibit emergent non-equilibrium behavior due to activity-induced effective interactions between the active particles. Here we study the aggregation and dynamical behavior of active rotating particles, spinners, embedded in 2D passive colloidal monolayers. Using both experiments and simulations we observe aggregation of active particles or spinners whose behavior resembles classical 2D Cahn–Hilliard coarsening. The aggregation behavior and spinner attraction depend on the mechanical properties of the passive monolayer and the activity of spinners. Spinner aggregation only occurs when the passive monolayer behaves elastically and when the spinner activity exceeds a minimum activity threshold. Interestingly, for the spinner concentrations investigated here, the spinner concentration does not seem to change the dynamics of the aggregation behavior. There is a characteristic cluster size which maximizes spinner aggregation by minimizing the drag through the passive monolayer and maximizing the stress applied on the passive medium. We also show a ternary mixture of passive particles and co-rotating and counter-rotating spinners that aggregate into clusters of co and counter-rotating spinners respectivelyThis work was supported by Department of Energy BES award #ER46919 (theoretical and simulation work) and the Chang Family (experimental work)

Elasticity-induced force reversal between active spinning particles in dense passive media

The self-organization of active particles is governed by their dynamic effective interactions. Such interactions are controlled by the medium in which such active agents reside. Here we study the interactions between active agents in a dense non-active medium. Our system consists of actuated, spinning, active particles embedded in a dense monolayer of passive, or non-active, particles. We demonstrate that the presence of the passive monolayer alters markedly the properties of the system and results in a reversal of the forces between active spinning particles from repulsive to attractive. The origin of such reversal is due to the coupling between the active stresses and elasticity of the system. This discovery provides a mechanism for the interaction between active agents in complex and structured media, opening up opportunities to tune the interaction range and directionality via the mechanical properties of the medium.United States. Dept. of Energy. Office of Basic Energy Sciences, Division of Materials Science and Engineering (Award No. #ER46919

Systems and methods for detecting molecular interactions using magnetic beads

Systems and methods are provided for detecting or measuring binding affinity between different compositions. The methods include contacting one or more magnetic beads having a surface including a first composition with a substrate having a surface including a second composition; applying a rotating magnetic field to the one or more magnetic beads effective to cause the one or more magnetic beads to move across the surface of the substrate; measuring the movement of the one or more magnetic beads across the substrate surface to determine a translational velocity; and determining a binding affinity between the first and second compositions from the translational velocity

Artificial Tribotactic Microscopic Walkers: Walking Based on Friction Gradients

Friction, the resistive force between two surfaces sliding past each other, is at the core of a wide diversity of locomotion schemes. While such schemes are well described for homogeneous environments, locomotion based on friction in inhomogeneous environments has not received much attention. Here we introduce and demonstrate the concept of tribotaxis, a motion that is guided by gradients in the friction coefficient. Our system is composed of microwalkers that undergo an effective frictional interaction with biological receptors on the substrate, which is regulated by the density of such receptors. When actuated stochastically, microwalkers migrate to regions of higher friction, much like a chemotactic cell migrates to regions of higher chemoattractant concentration. Simulations and theory based on biased random walks are in excellent agreement with experiments. We foresee important implications for tribotaxis in artificial and natural locomotion in biological environments.MIT Energy Initiative (BP Fellowship)United States. Dept. of Energy. Office of Basic Energy Sciences (Award ER46919

Mechanically transduced immunosorbent assay to measure protein-protein interactions

Measuring protein-protein interaction (PPI) affinities is fundamental to biochemistry. Yet, conventional methods rely upon the law of mass action and cannot measure many PPIs due to a scarcity of reagents and limitations in the measurable affinity ranges. Here, we present a novel technique that leverages the fundamental concept of friction to produce a mechanical signal that correlates to binding potential. The mechanically transduced immunosorbent (METRIS) assay utilizes rolling magnetic probes to measure PPI interaction affinities. METRIS measures the translational displacement of protein-coated particles on a protein-functionalized substrate. The translational displacement scales with the effective friction induced by a PPI, thus producing a mechanical signal when a binding event occurs. The METRIS assay uses as little as 20 pmols of reagents to measure a wide range of affinities while exhibiting a high resolution and sensitivity. We use METRIS to measure several PPIs that were previously inaccessible using traditional methods, providing new insights into epigenetic recognition