Nanoparticle Robots: No Assembly Required

What do foams, ice cream, pillows, blood, and cell membranes have in common? They’re all types of soft matter. Soft matter is exactly what it sounds like, materials that are quite literally soft, making them easy to deform. A key feature of soft matter molecules is their size. They’re “intermediate” in size meaning they’re larger than individual atoms but smaller than grains of sand. Crucially, soft matter molecules can self organize themselves into highly complex structures such as the proteins, polymers, and enzymes that are the building blocks of life. Scientists are trying to understand and emulate how soft matter particles are able to form such intricate structures. 

Daniela Kraft is an associate professor of soft matter physics at the Leiden Institute of Physics (LION) at Leiden University who studies self-assembly in biological and soft matter systems. Experimental and theoretical physics are the two prongs of research at LION. The institute also has three primary research areas: quantum matter and optics, cosmology, and biological, soft and complex systems. 

The Kraft Lab creates simplified nano models to investigate how complex biological structures are formed. “We use these little colloidal nanoparticles to model biological structures. So instead of studying a protein with a complex shape and many different interactions, we make a simple model using sphere shaped particles that we design. We look at what the spheres do, how they interact and come together to form functional structures, and it gives us new insights into the biological system,” she explains.  

One of the things Daniela’s group is looking at right now is flexible structures. They’re using particles that have the ability to act as joints and hinges to create structures with flexibility. These structures are then able to use motor particles to bend their joints and change their shape. “The ultimate dream is that we can use flexible structures to build a little robot,” Daniela explains. “You’d have arms connected by these joints and hinges and it would be driven by a motor particle. We could send these little robots to specific points in the body and have them deliver drugs or repair cells. It sounds really far away, and a complex robot is far away, but we have motor particles, we have these hinges, and we can put them together. So the simplest way of doing it is actually reasonably within reach.”

The freedom that Daniela gets from LION and the university allows her to work towards big goals like this. Unlike some other European universities, assistant and associate professors at Leiden University aren’t managed by full professors. Instead, tenure track faculty run their own independent research groups. They are supported by the university’s structured tenure track training and mentoring program which help them develop into successful PIs. “You're not just thrown in the water and told to swim here,” Daniela says. “The department knows that it can be tough, so they give you tools to help throughout the process. It's a nice way of doing it, and it continues once you get tenure,” she says. 

Outside of the lab, Daniela is active in the scientific community and has been recognized for her outreach work aimed at increasing the number of women in physics. When it comes to her group, Daniela usually has 50% or more female students and she has actively recruited female PhD students and postdocs in the past. She also believes it’s important to be a role model for her students and she personally benefited from female role models throughout her career. “I used to think that I was so dedicated to physics that I didn't need female role models,” she says. “But when I was doing my PhD, I saw very successful women in physics for the first time and I saw young women in my field taking the path to become a professor. It was very inspirational to see and I watched them very closely, much more closely than I watched the men. I think being a woman myself in the department is already making a difference here.”

Daniela and her colleagues also organize an annual Physics and Astronomy Ladies Day, an open day exclusively for female students interested in coming to Leiden to study physics and astronomy. The open day has been extremely successful. “Whereas normally we get like 80 men and 20 women, at the open day for women we get around 100 women. And we tell them the same things that we tell the male students, but we say it in a way that research shows us appeals more to women,” says Daniela. Physics can be a challenging course of study, however emphasizing the program’s toughness often discourages highly qualified women from applying. “Instead we say that if they have certain grades and like physics, they will be successful in our program. We want them to feel encouraged and not discouraged,” explains Daniela.