An economical process for constructing such 3D microstructures would be to "program" the constituent parts to spontaneously come together and build the structures themselves. Driving micron to mesoscale components (roughly between 0.1 to 100 millimeters) to line up and dynamically assemble into the desired structures, however, remains an elusive goal.
By engineering the fluid flows, researcher Shklyaev could drive the self-organization of a cube and the closing of the cube’s lid, so that the entire structure resembled a takeout box (Figure 1). The chemically generated fluid flow acting on the panels (through mechanisms knows as solutal buoyancy and diffusioosmosis) eventually reaches a dynamic steady state as it completes the assembly of the object, which could later be removed out of the fluid and maintain its integrity.
To further illustrate the potential of the fluidic machinery, the tops of each panel were decorated with long whiskers. As the panels fold upward and the whiskers extend into the fluid flow, the resulting forces drive the whiskers to rotate, much like moving propellers (Figure 2). Sticky bonds could be added to the whiskers to attract bacteria or other materials that need to be removed from the system.
Converting chemical energy into mechanical action
"One of the fundamental challenges in building anything with micron-sized building blocks is to get the blocks to robustly organize on their own, with little intervention from external tools, which could interfere with the dynamic self-assembly," Balazs explained. "What’s wonderfully brilliant about the system that Oleg designed is that the naturally occurring interplay between the fluid and chemistry performs the work to spontaneously construct a robust system."
Via computer modeling, Shklyaev designed two-dimensional polymeric sheets with one heavier sheet forming the foundation or base, and the other lighter sheets as the construction panels. Sticky bonds are added to specific points on the sheets to act as hinges and which are designed to precisely fit together.