 | Dr Yufeng WANG Assistant Professor of Department of Chemistry
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Q: What do you think are your most significant research accomplishments, and what has been the impact of your research?
A: I am a colloidal scientist working on colloids, which are tiny particles 1/100th the size of human hair. Colloidal particles not only can be found in everyday items such as paint, milk, glass and porcelain, but also are crucial building components for constructing functional materials with advanced photonic, optical, and mechanical properties. Unlike atoms and molecules, which have a predictable way of arranging themselves, colloids are uniformly sticky across their spherical surfaces and assemble in non-specific ways, making it difficult to design and assemble three-dimensional (3D) structures from these particles. To tackle this problem, I have developed a strategy to create Colloids with valence, which are particles with surface patches so that they assemble into predictable structures just like atoms combine to form molecules. This work has been the one of the most significant accomplishments of mine, which gives scientists tremendous flexibility to design three-dimensional structures and materials, for example, light-weighted materials with open structures. The concept of atom-mimicing particles have also stimulated many researchers to develop new strategies to fabricate them. Recently, following these advances, the formation of colloidal diamond structure has been realized, one of the most desirable structures for making photonic crystals in the visible wavelengths. This holds promises in generating the next generation of optical and communication devices with wider bandwidth and less energy loss.
Q: Please give a brief description of 1 - 2 ongoing research projects that best reflect your visions in the scientific field.
A: The desire to change is the very driving force for innovation. Currently, my research group works on various exciting projects to improve and or even fundamentally change the way colloidal particles bind and assemble. In one project, we use metal-organic frameworks (MOFs)—highly functional and addressable molecular materials—as the colloidal particles. Conventionally, colloids and nanoparticles are made from plastic and silica, etc., they are spherical in shape and their properties cannot be tuned easily. Using MOF-based particles, we can coordinate the structures of materials across various length scales, meaning that we can control materials’ architecture on different levels. In addition, the MOF particles are crystalline and have a spectrum of polyhedral shapes, which provides rather different modes of packing. So far, we have built a variety of 1D-3D materials and demonstrated their application in controlling light. In another project, we are fabricating active colloids. These new particles contrast traditional passive particles by having the ability to propel like micrometre-sized motors and assemble like schools of fishes or flocks of birds. They consume energy as they move and organise, like living system in nature, whereas passive particles normally rely on surface charges (for example) to bind. Such systems are potentially useful to mimic out-of-equilibrium systems for making dynamic smart materials that adapt and reconfigure.
Q: What is the most important question you want to address?
A: We live in the era of big data where we are witnessing an explosion of information that poses increasing challenges to data processing, transportation, and storage. With semiconductor devices based on silicon and electrons pushed to their miniaturization limit, more and more attention has been focused on photonics, which uses photons as information carriers and have a much wider bandwidth as well as less energy loss. However, photonic materials having complete omnidirectional band gap—needed for light manipulation—are extremely difficult to fabricate, particularly for those with band gaps in the optical (visible) range.
The self-assembly of colloidal particles a few hundred nanometer in size is a promising approach to construct such materials from the bottom up. Despite some recent progress, there are still many pressing challenges that need to be tackled, which comes down to how to synthesize, control, and manipulate tiny nanoparticles to form structures by design. The problem is fundamental and interdisciplinary, requiring expertise from various fields including chemistry, chemical engineering, physics, etc. A major challenge is how to encode information into the particle systems, either via shape, surface patterns, colloidal interactions, kinetics, etc., so that the particles are intelligent enough to make their own decision in the beaker and form the right structures. With these designs and tools, we will be able to pursue the goal of fabricating all sorts of new materials, or improve the properties of traditional materials.
Q: Where do you see yourself in five years/ten years? What do you want to accomplish the most?
In five years, my goal is to establish a series of new colloidal platforms that allow us to tackle the most pressing challenges in colloid science or materials science in general. Being a crucial material, colloids and nanoparticles have been around for centuries, yet the number and kinds of structures one can assemble remains limited, far from what atoms and molecules can achieve. Much of our effort will be focused on introducing sophisticated low-symmetry particles so that more information can be incorporated to direct the particle assemblies and structure formation. In organic chemistry, people can create molecules’ atomic resolution, meaning the position and connection of each atom are well controlled; for colloids, such precision and programmability are highly desirable. The new systems and the potential discoveries should help build a leading position in the relevant fields on an international level. In the longer term, for example, 10 years, we wish to witness the real applications of the colloidal materials we develop. These includes colloidal painting that show tunable color without organic dyes, colloidal robotics that carry therapeutic agents to treat diseases, colloidal crystals that reconfigure, or even microchips based on colloids and light. Because colloids have been employed as models to study fundamental physics, our systems will help elucidate crystallization process and phase transitions.
Q:What are the challenges you are facing?
A: As a young independent researcher, there are multi-faceted challenges that need to be dealt with. Mentoring graduate students, delivering lectures, coming up new ideas, applying for grants and publishing papers. While these different tasks can lead to a lot of pressure, I feel accomplished when I was able to handle them. Most importantly, I can always discuss ideas with under- and post-graduate students on topics of our interest. This drives me and our innovation.