Scaling-up and -down in a nature-inspired way

The ongoing revolution at the nanoscale can be brought to good use only if the microscopic and macroscopic worlds are properly connected. This problem has received remarkably little attention in chemical engineering: Designs focus on the molecular and nanoscales, while scale-up is typically treated empirically, lacking rational design at the mesoscale. Where structured designs are used, the term is quasi-equivalent to periodic repetition of the basic unit. Multiscale modeling is challenging when it is applied to heterogeneous systems that are inherently difficult to scale. Chemical innovation needs to be matched by chemical engineering innovation. Nature provides us with excellent examples to address the scaling issue. Promising are hierarchical designs, e.g., involving fractal networks, possibly combined with periodic assemblies. Dynamic self-assembly, source of many natural patterns, is another potential route. Although the examples discussed here focus on multiphase processes, the proposed nature-inspired chemical engineering approach applies equally well to the design of hierarchically structured products.