“We want to make the un-makable”

Daryl Yee, a newly appointed Tenure Track Assistant Professor at EPFL’s School of Engineering, belongs to the next generation of researchers exploring the intersection of materials science and advanced manufacturing. Radiating infectious inquisitiveness and living by the adage “we want to make the un-makable,” his curiosity and drive are reminiscent of the alchemists of old. The choice of the term “ALCHEMY” for the abbreviation of his Laboratory for the Chemistry of Materials and Manufacturing is a daring statement. As he says,

I named my lab ALCHEMY to invoke a feeling of magic and wonder in what we do.

Born in Singapore, Yee’s academic trajectory has taken him through various phases of materials exploration across the globe—from metals in London (UK), then polymers in Pasadena (California, USA) to nanoparticles in Cambridge (Massachusetts, USA). During his graduate school years at Caltech, his penchant for “making” emerged. Confronted with the limitations of working with commercially available materials for his projects and steeped in the school’s interdisciplinary culture, he was pushed by his mentors to learn how to use chemistry to make materials himself.

When posed with the challenge, “Why don’t you just make it yourself?” little could Yee’s mentors surmise the surprising trajectory they put the young researcher on. For his PhD work at Caltech, what started with making materials for biomedical devices evolved into making all kinds of functional materials for additive manufacturing. “And I became very interested in how to make materials, both at the nano- and macro-scale. This eventually led to one of my favorite works, where I figured out a simple method of 3D printing both ceramics and metals out of polymers,” he tells us.

It sounds and looks like magic, but it’s really grounded in fundamental materials science!

Metal out of plastic? That does indeed sound like magic. Yee explains, “To make metals out of polymers, we start by 3D printing a hydrogel that is then swollen, or infused, with a metal solution, for example copper nitrate. You then get this blue colored hydrogel that’s basically just water, dissolved copper salts, and some amount of polymer. You then heat it up to remove the polymer and convert all the copper nitrate to copper oxide, which can then be reduced again to copper. It sounds and looks like magic, but it’s really grounded in fundamental materials science!” Because the hydrogels can be swollen with almost any kind of metal salts, one hydrogel has the potential to be transformed into an almost infinite number of materials. By infusing the hydrogel after printing, the material of the printed structure is decided after printing is complete — a complete 180 from conventional methods where the material is selected prior to fabrication.

Yee also has a penchant for nanomaterials. His postdoc work at MIT brought him into contact with the field of nanoparticle superlattices, where he learnt how to self-assembly nanoparticles into ordered structures, similar to atomic crystals. He’s currently exploring how to combine self-assembly and 3D printing to make materials with unusual structures and properties. Yee believes that materials science can be a force for good, for not only does he “want to make the un-makable,” he also believes in “Advanced materials for all.” Going on to say that “if we can simplify the chemistries and processes such that anyone with a 3D printer can use it to make whatever material or device they need, then we empower them to solve their own challenges.” And his enthusiasm is contagious. One almost wants to rejoin with “And all for advanced materials!”

Advanced materials for all!

At EPFL, Yee seeks to continue his work on developing advanced materials with tailored form and function. His group is currently focused on developing new polymer-based methods for ceramic, metal, and composite printing; designing polymers with dynamic, shape-changing properties; and developing processing and synthetic strategies to make materials with complex microstructures and properties. “To accomplish all of these projects, we’re doing everything from making molecules to building printers!”

When Yee’s teaches his first class, Materials Implementation, this semester, his calm yet effervescent excitement will surely spill into the classroom. But he is slightly apprehensive as he describes his ambitions for this core-skills class for microengineering bachelor students, with hundreds of attendees in a vast lecture hall. “I’m hoping to be able to walk the line between understanding how materials are used and the materials science that explains why these materials have the properties that they do,” he says. He also recognizes that while the class is focused on materials engineering and application, he thinks the students still need to know the fundamental materials science, and hopes his expertise can bridge the gap.

I’m hoping to be able to walk the line between understanding how materials are used and the materials science that explains why these materials have the properties that they do.

As he strives to bridge this gap in teaching and research, Daryl Yee embodies the forefront of materials science—a solid understanding of the underlying science in the pursuit of innovative applications, imbuing his field with a sense of wonder typically reserved for the arts. With a career that has spanned continents and disciplines, he brings a unique perspective to EPFL. His work, grounded in a profound understanding of materials science and engineering, transcends traditional boundaries, allowing for the creation of new materials with a variety of applications. As he steps into the role of educator, Yee carries with him not just a deep understanding of his discipline, but a fervent desire to make the sophisticated world of material fabrication accessible to all.

Yee's method, characterized by clarity, experimentation, and enthusiasm, is likely to inspire a new wave of innovation in the field. In this spirit, the addition of Daryl Yee and his ALCHEMY laboratory is a welcome injection of new, bold ideas to design materials and democratize manufacturing and spur the exploration of yet uncharted scientific seas at EPFL.