(392c) An Ipad-Based Brownian Dynamics Simulator for Electrokinetics in the Classroom

Tablet-based computing platforms offer enormous potential to provide immersive education experiences by virtue of their unique combination of a graphical environment and touch screen interface. Here we describe our efforts to exploit these features by porting a conventional Brownian dynamics simulation into an Apple iPad application that provides a visual representation of polymer coil size, relaxation phenomena, Brownian motion, and transport under an external driving force (i.e., electrophoresis). 

Our app employs a coarse-grained bead-spring model of the polymer chain, enabling the user to customize the number of beads and their positions to define an initial polymer conformation. The user can choose between infinite and finite extension models for the connecting springs. The app’s core simulation module provides two functions. First, in the free solution simulation mode, it mimics the polymer’s Brownian evolution toward an equilibrium state. Key parameters continuously reported during the simulation include radius of gyration Rg, end-to-end length L, largest and smallest spring lengths, and contour length (determined from the average spring length). Secondly, the app is capable of simulating the polymer’s response when a user moves individual beads by touching the screen, with force proportional to the speed of the user’s finger swipe on the screen. This capability can be used to visualize the process of polymer stretching (single bead drag) or electrophoretic transport (whole polymer drag). 

The app-based format makes it possible to visualize polymer dynamics in an appealing way and offers a useful tool to illustrate fundamental concepts involving polymer physics.