One of the current challenges in science and engineering is to understand and control the behaviour of matter and energy at distinct length and time scales. In many chemical processes, atomic, molecular, photonic, and electronic events occur in femtoseconds at a surface site. This nanoscale activity is connected to processes running in seconds at the mm scale in a bulk continuum, via a stepwise sequence of intermediate-scale architectures and phenomena. Mass transport in the fluid is generally well understood and can be modelled to the finest detail. For many systems also the chemistry at the nano-sized (catalyst, adsorption) site is known, from ideal model systems. The crucial link between the two regimes is formed by phenomena at the mesoscale, defined as being between the size of a molecule and several µm, the size of a representative amount of bulk material.
The management of mesoscale dynamics is the missing link in gaining complete control over chemical processes like heterogeneous catalysis. The ability to accurately position nanoscale active elements in cellular mesoscale (nm to µm-range) structures with high symmetrical order is instrumental in streamlining vital molecular or energetic paths. 3D periodicity in the structure that supports active or adsorption sites minimizes spatial variations in mass transport, whereas mesoscale control of the location of these sites gives a route to tuning activity and functionality. The introduction of mesoscale metamaterials expands the on-going trend in chemistry, of more and more dimensionally refined structured elements, a so to speak "Moore's law in Process Intensification". The roadmap to higher process efficiency dictates a next, disruptive step in mastering manufacturing control at smaller dimensions. om in shape, symmetry and composition.
To realize the required paradigm shift, active (catalytic or photoresponsive) nanoparticles will be positioned at nanometer-precise optimal distances on an optimized ordered and open 3D supporting architecture, which ensures that all molecules flow through the material at the same speed, whereas they also experience exactly the same interaction with the nanoparticles. The game-changing technology to achieve this is by additive manufacturing.
For the above innovation to become real, two major, crucial advances in fabrication technology have to be created, which are the main objectives of this project:
Objective 1. Electrospinning of complex nanowires with complete freedom in the choice of wire material or material combinations, dimensions, porosity, and surface properties, and complete freedom in the type, shape and relative position of the nanoparticles along the nanowires. In all electrospun nanowires reported until today, the nanoparticles are randomly and inhomogeneously positioned on the wires, because the particles form from dissolved ingredients during deposition and calcination or are applied by a post-deposition step. The electrospinning method itself does not offer a mechanism to control the position of particles in the wire, and a real breakthrough is needed to arrive at Objective 1.
Objective 2. Positioning and connecting uniform electrospun nanowires via localized and switched electrical fields, with nanoscale precision on a 3D grid to create ordered cellular materials of sufficient mechanical stability for chemical applications. Electrospinning is a cheap and unique technique, with excellent industrial perspective, to produce fibres with a diameter in the range from less than 3 nm to several µm, and is based on a jet created by an electric field (~1kV/cm) between a dispenser outlet and a collector, where solid wires form in a solidification process. Due to an electrically driven bending jet instability, electrospinning mostly produces randomly positioned nanowires, and as yet not a single demonstration of nanoscale precision in 3D has been given. Definitively also a major breakthrough is needed to arrive at Objective 2.
