Maze Solving Using Fatty Acid Chemistry

This study demonstrates that the Marangoni flow in a channel network can solve maze problems such as exploring and visualizing the shortest path and finding all possible solutions in a parallel fashion. The Marangoni flow is generated by the pH gradient in a maze filled with an alkaline solution of a fatty acid by introducing a hydrogel block soaked with an acid at the exit. The pH gradient changes the protonation rate of fatty acid molecules, which translates into the surface tension gradient at the liquid–air interface through the maze. Fluid flow maintained by the surface tension gradient (Marangoni flow) can drag water-soluble dye particles toward low pH (exit) at the liquid–air interface. Dye particles placed at the entrance of the maze dissolve during this motion, thus exhibiting and finding the shortest path and all possible paths in a maze

Swarming Behavior of Gradient-Responsive Colloids with Chemical Signaling

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q-GRID: A New Method To Calculate Lattice and Interaction Energies for Molecular Crystals from Electron Densities

We present a new method to calculate lattice and intermolecular interaction energies for molecular crystals from electron densities obtained within the crystalline environment: <i>q</i>-GRID. The electron density is partitioned over a grid, and each grid point is assigned to a specific molecule. Intermolecular interaction energies are calculated as a sum of Coulomb interactions between grid points and nuclei of pairs of molecules and analytical dispersion and repulsion contributions. An advantage of this method is that the interactions within a molecule are automatically excluded. After a description of the new method and the computational setup, three test cases representing different classes of molecular crystals are presented: anthracene, isonicotinamide, and dl-methionine. For the polymorphic compounds, <i>q</i>-GRID is able to obtain the correct ranking of the polymorphic stability. Calculated lattice energies, as a sum of intermolecular interactions, are in good agreement with sublimation enthalpies. The code of <i>q</i>-GRID is made publicly available