3.10 Catalytic Molecular Pump and Molecular Machines. The design of molecules with dynamic functionality has been extensively described as 'molecular machines' with both synthetic and biological examples . While 'switchable catalysts' are capable of turning on and off as needed , other molecular machines and molecular devices are capable of implementing motion including molecular motors and pumps . For example, an artificial molecular pump is capable of moving molecules such as charged rings up a concentration gradient , conceptually similar to nature's capability for controlling the mobility of metal ions across membranes against equilibrium . These molecular machines and pumps are relevant to the dynamic oscillating catalyst surface concept addressed in this work due to a common mechanism. Of the many methods of manipulating molecules, many molecular machines and pumps utilize energy to implement a dynamic 'pulsating' ratchet energy profile . Similar to Figure , progression along a pulsating ratchet permits molecules to spontaneously access the current low energy states; the input of energy into the ratchet system alters the free energy landscape permitting molecules to access new low energy states that constitute progress in position (i.e., molecular pumps). The evolution of changing energy profiles biases progress in one direction based on local peak heights, consistent with its 'ratchet' name .