Kai Zhang, assistant professor of chemistry at Duke Kunshan, conducts computational studies into soft matter. Photo by Qiling Wang
By Lei Qi
Staff writer
Few research areas have such wide-reaching implications, or produce results that are as difficult to predict, as soft matter. Then again, Kai Zhang likes a challenge.
Zhang, assistant professor of chemistry at Duke Kunshan, began taking an interest in soft matter while studying for his Ph.D. at Duke University. He was attracted by its broad application and, as it’s a relatively new area, the many unanswered questions it presents.
Put simply, soft matter surrounds us. The term refers to any material that can be altered by thermal fluctuations or other external forces. These materials occupy the middle ground between the solid state and the fluid state, such as liquid crystals, gels, polymers, particulate matter and skin.
Zhang carries out theoretical and computational studies to understand and predict the structural and dynamical properties of soft matter through molecular simulation and machine learning. Since joining Duke Kunshan, he’s also been helping undergraduate students explore and publish research in the field.
‘In the scientific community, soft matter is described as where physics meets chemistry meets biology,’ said Zhang. ‘It requires a high level of interdisciplinary research. Breakthroughs can have a profound effect on life sciences, chemical engineering, medicine, environmental science, and much more.’
For years, physicists, chemists and biologists involved in soft-matter research worked in silos. That began to change in 1991 after French physicist Pierre-Gilles de Gennes received the Nobel Prize for physics. His acceptance speech opened the eyes of scientists across disciplines, leading to more joined-up thinking.
Still, it hasn’t made the research any less difficult. Throughout his time at Duke, his postdoctoral research at Yale and Columbia universities, and now at Duke Kunshan, Zhang has been reminded time and again that there are no easy paths to scientific success.
‘I’ve had research come to a dead end and I’ve needed to start over, or sometimes the project lasts twice as long as expected,’ said Zhang. He stressed that it’s important to stay positive. ‘There are so many things to worry about in life ‘ health or family well-being. Research setbacks are not a big deal. Ph.D. training is all about solving problems. You need to push on.’
He said many of his classmates grew frustrated and switched to software engineering, an easy transition due to their research involving a lot of programming. Zhang also dipped his toe into the world of industry, but his heart was always in academia. In the 11 years since receiving his undergraduate degree from Beijing’s Tsinghua University, he has published more than 20 papers, with his findings cited over 500 times.
Clockwise from top left: Kai Zhang’s molecular simulation of minimal surfaces; Penrose tiling; Zhang’s molecular simulation of polymer conformation; a seal once owned by Dugu Xin
Zhang said he makes sure his students know how tough scientific research can be by setting tem challenging topics and tasks.
‘DKU students have an excellent foundation and are very quick to learn. I’m very fortunate to have them as my undergraduate researchers,’ he said. ‘They’re all adults. They need to think independently. If they run into trouble, I try to speak in a language they can understand, to help them catch up.’
Human connection
In addition to bridging divisions within natural and applies sciences, Zhang also sees many connections between science and the humanities.
Along with links to research papers, codes and conferences, Zhang’s personal website has a section on his favorite artworks, including a 26-faced jet seal once owned by Dugu Xin, a prominent general in the Western Wei period (535-556), and a plaster model of the thermodynamic surface designed by Josiah Willard Gibbs, founder of statistical mechanics.
‘A lot of artwork has underlying scientific laws. It’s not a coincidence. It keeps happening precisely because the laws are obeyed, which is a beautiful and interesting thing in itself,’ said Zhang. For example, he said, the physicist Roger Penrose, who won the Nobel Prize for his work on black holes, also discovered Penrose tiling, a decorative tiling system, while the faces on Dugu Xin’s seal match the orientation of a crystal.
A passion for history has also helped provide Zhang with insight into human nature and biological development.
He said he enjoys reading books like Sima Qian’s ‘The Records of the Grand Historian,’ written from 109-91 BC, and evolutionary biologist Jared Diamond’s ‘Guns, Germs, and Steel,’ which traces humanity’s journey over the past 13,000 years and attempts to explain why Eurasian and North African civilizations have survived and conquered others.
‘I don’t care about political conflicts and personal grudges hundreds or thousands of years ago. A historical event happens not by chance but because of many underlying reasons,’ he said. ‘I’ve struggled with some complex questions about human nature and social relations, but after reading these books, I realized that many evolutionary principles are playing a role.’
After a trip to Japan, Zhang said he read up on the country’s Warring States period and played online strategy games set during that time to understand the links between military supremacy and the amount of land controlled by various warlords.
Zhang said part of the reason he enjoys looking for such patterns in science, art and history is because it’s extremely challenging.
‘Working in academia is difficult. If you enjoy research, find you are good in one area, and are willing to go deeper, that’s great,’ he said. ‘But if you find your passion in research gradually waning, it’s OK to pursue a different path. It will be alright as long as what you do makes a positive impact on society.’
Zhang with undergraduate researchers Dingning Li (left) and Zhonghang Qu. Photo by Qiling Wang
Papers, presentations for undergraduate researchers
Zhonghang Qu ’23 began working as a researcher in Kai Zhang’s lab last year. In the summer, he conducted computer vision research in materials science, exploring the use of convolutional neural networks to study materials science images.
‘Professor Zhang connected me with the lab at Columbia University, where he did his postdoc research, and we ended up collaborating on the project. We have access to a large amount of data collected by Columbia,’ Qu said. ‘Under professor Zhang’s guidance, I read many research papers, developed my research design, and wrote the algorithms. I was able to use the DKU server remotely to build models and test performance.’
Zhang encouraged the sophomore student to write up his findings in a paper, and together they have been working on high-quality statistical diagrams. They plan to submit the paper to the international journal Macromolecules, with Qu as first author, Zhang as corresponding author, and co-authors from Columbia.
Yue Yu ’22 has enjoyed similar success since joining Zhang’s lab. After recently presenting his directed research on molecular dynamics simulations of gas diffusion separation in regular pores to university donors, he is preparing to present at the annual meeting of the American Physical Society.
