Endgame Drives King's Research

William King
William King

William King’s research into the thermal properties of materials has led to nationally-recognized innovations, including some that have uses in industries. Those practical applications of his work are what drive King’s efforts.

William King tells the story of meeting his wife’s family for the first time and finding himself in a situation that often confronts scientists and researchers: how to explain to strangers what it is they do.

“I said ‘I work on technology that is so small you can’t see it’ and they said ‘sure you do,’” King said with a laugh. He said he then offered a general introduction to his research work. “The properties of materials depend on temperature, so I start there.”

King is an Associate Professor in the Mechanical Science and Engineering Department at the University of Illinois and a member of the 3-D Micro- and Nanosystems group at the Beckman Institute.

As Director of the Nanoscale Thermal Processing Laboratory at Illinois, King’s research involves basic science questions surrounding thermal properties of materials, as well as the design, fabrication, and use of innovative tools for thermal and thermo-mechanical processing at the micro- and nanometer scales.

“The focus of my research group is to understand how heat flows and affects materials,” King said. “Then we build tools to measure and understand those processes and we exploit applications of those tools and processes.”

It may not always be easy to describe what he does to the general public, but the results of King’s research could very well be affecting a large part of the population in the next few years.

The fields in which I do work move very quickly. I’m really focused on innovation. I want to identify an opportunity that I think is important and that nobody is doing and see if we can make an impact.
– William King

In 2006 King was named to Technology Review magazine’s annual Young Innovator list of people under the age of 35 whose innovations are likely to change the world. The award described the nano-soldering iron King’s lab developed, but that technology is just one of many he has been working on that have a wide variety of real-world applications. King’s research tools and insights into thermal properties at the nanoscale have been used in the automotive, pharmaceutical, chemical, and energy industries.  

“In any energy production, power production, energy transmission, energy storage in batteries or fuel cells, temperature plays a key role,” King said. “In a lot of modern technologies, temperature at very small scales plays a role.”

As an example, King mentioned pharmaceuticals and the role thermal properties play as drugs degrade over time at room temperature.

“In the world of thermal analysis, aspirin and acetaminophen are some of the standards you measure first when you try out a new thermal analysis technique,” he said. “The way that these materials age is they age at the nanometer scale first. So, having tools to understand the aging at very small scales tells you something about the macroscopic performance of the material. It is an early detector for learning about the fundamental physical properties of the material.”

That also applies to measuring the drying qualities of paint, which is one of the applications for which his work has been used.

“Watching paint dry is a joke about one of the most boring things in the world,” King said. “It turns out that it is an enormously challenging thing to understand how paint dries. Our technology is used by the coatings industry, people that are developing new paints for automobiles. They take our thermal probes and they poke at the paint to see if it is really dry, if it is really as hard as it should be, as thin as it should be, if all the solvent is gone.”

That kind of end-of-the-research-line application is what guides King’s work.

“I’m always trying to do something different,” he said. “The fields in which I do work move very quickly. I’m really focused on innovation. I want to identify an opportunity that I think is important and that nobody is doing and see if we can make an impact. If we can move the ball I want to do that and if we can’t, then I want to get out.”

As an example, King mentioned his work in the area of thin film polymers. As reported in a 2008 Science paper, King’s research showed that at very short length scales, polymers (used in everything from semiconductor devices to adhesives) behave in unexpected ways.

This is the kind of discovery which has implications for nanoscale manufacturing in numerous industries, but King says academic research in this area and the needs of industry don’t always match up. He said more than 100 groups worldwide are trying to do nanometer scale manufacturing using polymers, while a literature search will give thousands of academic journal articles on research into nanometer-scale polymer properties.

“Our group wants to understand the mechanical properties of polymers at the nanometer scale and the reason that we are interested in this is for nanomanufacturing,” King said. “The sociology of this particular field is very interesting because you have this enormous technological pull disconnected from a huge science footprint. Not a single one, out of the thousands of those papers that have been written, will teach you something you need to know about the manufacturing that’s relevant to these problems.”

King saw that gap as an opportunity to do original research in this area.

“We did a very careful measurement of mechanical stress and strain as a function of temperature for very thin polymer films,” he said. “What we found was that the thin polymer films have mechanical properties that can be substantially different from what you would expect from your materials science textbook.”

In another research line, King and Beckman colleague Rohit Bhargava created a technique, using one of King’s nanoscale probes in an atomic force microscope, that was able to perform structural and chemical characterization of samples at the femtogram level. They reported on their original discovery in a paper in Analytical Chemistry in 2008.

The use of tools like nanoscale probes and soldering irons is central to King’s work. One of the thermal processing tools he has developed has a very sharp tip of just a few nanometers; it can be used as a tiny soldering iron or a tiny glue gun for manipulating, melting, and depositing very small quantities of materials for uses in electronics, detectors, and other applications.

“It turns out that this is very useful because the heating can turn on and off this material manipulation,” King said. “In competing technologies there are not strategies for the on/off. This is really a critical aspect for scaling up to industrial relevance.”

The ability to use small tips in various ways means they can also be a tool for performing what is called maskless lithography, a method that doesn’t require creation of a template for doing nanolithography.

“Most lithographic techniques require a template ahead of time, whether that template does embossing or material transfer or is a mask for light or funnels electromagnetic waves,” King said. “In the mask-based techniques, you have to figure out how to make the mask. In maskless methods you do writing in a direct way. You can make anything that you want at any time that you want.”

King said the nanolithography tool is “starting to become a pretty mature research tool” that is on the path toward commercialization. He said it could be used to process materials for doing nanolithography in the optical, electronics, and energy fields. Again, King is looking toward how his research might be used in the real world.

“Somebody has to use your stuff at some point or you haven’t been a very good steward of the resources that you’ve been granted,” he said. “Somebody has to care about it at some time and maybe that’s not for 20 years. My research philosophy is that I want to be careful about picking problems, so that I can see the endgame. I don’t take on a single problem where I can’t see the endgame.

“My graduate students are convinced that I have a master plan,” King added with a laugh. “I’ll let them think that.”

While the potential impact of his work may guide his choice of research lines, King’s work with his students is a foundation of all that he does at the University.

“I’m proud of all the students that have come out of my research program,” King said. “I put a lot of energy into matching students with things that they can be good at. When I have a new student, we start doing things and I learn about them and they learn about me and you try to let their project grow.

 “The best part of the job for me is working with my students.”

That is especially true when it comes to seeing a student go from classroom to laboratory to doing research. King said there is always one meeting with every student in which the relationship transitions from professor and student to lead researcher and budding researcher.  

 “After those students have worked with you for awhile, they come in and show you their result and say ‘OK, what should I do next what?’ There is one meeting where you say ‘I have absolutely no idea what that means and I have absolutely no idea what to do next,’” King said with a laugh. “Sometimes you get this little sense of panic from the student, like ‘what do you mean you don’t know.’ That’s when I say ‘now we’re doing research.’ That’s with every single student. That’s a great moment. Then it gets fun.”