Flexible solutions: the advantages of organic materials

19 October 2016

Nathan Wang’s (Croucher Scholarship 2014) interest in materials science was first piqued by work on stimuli-responsive polymers as an undergraduate student, which in turn inspired him to study chemistry. The synthetics lab where he worked focused on introducing mechanical bonds onto polymers and manipulating mechanical properties to respond to stimuli, e.g. changing the pH conditions of the material to increase elasticity.

This research showed more potential for scientific exploration and direct application than standard chemistry classes, and encouraged Wang to pursue doctoral study in adapting organic material for electronics. 

"In the past, organic material has mostly been developed to be semiconductors, but now there are more candidates for semiconductors, and my current work looks at the advantages of organic material which has the potential to be infinitely stretchable,” Wang explains.

Chemistry primarily deals with organic materials made of carbon, oxygen, hydrogen, and nitrogen. While ‘electronics’ brings to mind metals, plastics, and other inorganic materials, organic electronics is a rising field which uses organic materials for devices.

Stretchable polymers

Dr Zhenan Bao’s lab at Stanford University utilises the basic principles of chemistry, physics, engineering, and material sciences for novel applications such as flexible, stretchable electronics and energy devices. The innovative interdisciplinary environment is pushing the boundaries of stretchable semiconductor polymers like electronic skin, perfect for Wang’s focus on the stretchable component of polymer engineering.

Most devices nowadays have a semiconducting component and most of this is still silicon-based and rigid. Wang’s research is part of the movement to replace silicon with stretchable organic materials and polymers, starting with simpler devices, which do not require high computing power, such as computers.

There is a particular need in medicine for cheaper, accurate, and less intrusive electronic devices like wearable patches to monitor body functions. However, lightweight electronics are always more ideal, and elastic electronics as an entirely new class has many applications not yet thought of.

The structure of a layer of graphene

For example, the lab’s wearable sensor monitoring body temperature is made of plastic material embedded with nanoscale spikes. Coated with graphene, an atom-thick layer of carbon, and embedded in a thin film of elastic polyethylene, these spikes were adapted to regulate battery temperature, automatically shutting it down when too hot. Depending on how many spikes or the type of polymer used, researchers can set temperature levels and “smart” self-regulating processes.

Wang’s lab was also behind the development of the world’s fastest thin-film organic transistor, proving that organic semiconductors can perform at levels needed for high-definition television screens and the like, which still rely on silicon technology. 

Stretchable polymers can also be engineered to expand, contract, and self-repair, making them potentially invaluable for artificial muscles, medical implants, and wearable medical electronics.

Research on organic semiconductors started mostly as scientific curiosity and a natural progression of innovation, rather than a specific need, though the advantages are clear. Electronics are getting lighter, cheaper, and faster, but producing silicon wafers still carries a high cost.

Organic potential 

A huge motivation in looking at organic materials seriously was to lower production costs, but their performance levels still have to be improved. Since it is difficult to push organic semiconductors to that level, researchers like Wang working at the creative intersections of chemistry are called in to work their magic. 

Wang’s current project looks at engineering conjugated polymers, which have delocalised praseodymium (a rare earth metal) riddles along their backbones which make them more semiconductive, improving the electronic properties of materials. 

“Manipulating these polymers will allow us to expand on their natural potential for more innovative and commercial use. We can make flexible, stretchable, printable electronics which traditional silicon and metal-based systems cannot adapt to, and lower the cost of new technologies in the process,” Wang says.

Growing up in a scientific family, Wang has fond memories of visiting his mother in her lab and learning how things worked. Chemistry also gives him ample opportunity to follow his scientific interests, as the broadest field in the natural sciences. 

“Chemistry is like applied physics, and biology is like applied chemistry, so my work puts me in the position to get a glimpse of both worlds,” Wang says. 

Asked about future plans, he laughs, “My field is changing so rapidly, and I still have lots to learn, but for now the opportunities for applied research in academia seem like the best way to be at the forefront of these changes.”

Nathan Wang completed his undergraduate studies in chemistry at Wesleyan University, focusing on mechanically-interlocked polymers. He is currently a doctoral candidate in Stanford University’s Department of Chemical Engineering, and a recipient of a Croucher Scholarship in 2014. 

To view Wang's personal Croucher profile, please click here.