Versatile crystal growth for functional materials
AMOLF researcher Wim Noorduin and fellow scientists Nadir Kaplan, Joanna Aizenberg and L. Mahadevan of Harvard University have developed a model that can be used to accurately describe and predict the formation of a broad range of exquisite three-dimensional crystal structures. This provides the basis for a new, cheap and versatile production method for the manufacture of functional materials, such as light guides for solar cells. The research team presents its results on 31 March in Science.
The publication is the sequel to Noorduin's Science publication in 2013, when his beautiful microscopic 'crystal flowers' adorned the journal's cover. At that time, he was working as a postdoctoral researcher at Harvard University. In 2015, Noorduin returned to the Netherlands to set up a group at AMOLF in the area of Self-Organizing Matter (as part of the Designer Matter research theme). He investigates how chemical reactions and crystallisation processes can lead to new, microstructured functional materials. The Science publication is an important milestone in the research. "Four years ago, we were mainly enthusiastic about the versatility of the crystallisation technique," says Noorduin. "Now we also know how we can give practical relevance to it."
Functional shapes
In the current Science publication, Noorduin and his Harvard colleagues present a crystal growth model that describes with mathematical precision how parameters such as salt concentrations and acidity determine the shape of the crystals. The model therefore indicates how completely new, functional shapes can be produced. What is so unique about the precipitation system is that the shape of the micro-objects does not depend on the crystal structure of the embedded crystals. When salt or sugar is allowed to crystallise, it produces faceted crystals: the exterior reflects the arrangement of the atoms or molecules on the inside. Noorduin's method is not limited by this. "We got rid of the limitations of the crystal structure, so to speak, to provide ourselves with greater design freedom. The intrinsic crystal properties, however, remain unchanged, for example the ability to guide light."
One of the applications that Noorduin has in mind are photonic materials: materials that exhibit an unusual interaction with light. For example, he is currently producing spiral-shaped, light-guiding structures with a fluorescent light source in the base, as well as a wide range of vase-shaped structures. 'If you add a reflective coating to these vases, then they could function as a light concentrator for solar cells, for example.' Up until now, researchers have tried to produce such 'microvases' using high-tech material processing techniques such as lithography and micromachining. These 'top-down' manufacturing techniques are expensive and subject to limitations. Noorduin expects his 'bottom-up' approach to be cheaper and more versatile.
Further information can be obtained from: Wim Noorduin, +31 20 754 7347.
More information about this research on the AMOLF website.
Reference
C. Nadir Kaplan, W.L. Noorduin, Ling Li, R. Sadza, L. Folkertsma, J. Aizenberg, L. Mahadevan 'Controlled growth and form of precipitating microsculptures' Science, 355, 1395, 2017.