Meet the researcher: Dr. Roy Shenhar

Roy Shenhar

Roy Shenhar is an associate professor in the Institute of Chemistry. He holds a double major B.Sc. degree in Chemistry and Computer Science and received his PhD in Chemistry in 2002, all from the Hebrew University. After a postdoctoral period at the University of Massachusetts at Amherst (2002-2004) as a Fulbright scholar and another postdoctoral year at the Technion as a Zeff fellow (2005), he started his independent career at the Hebrew University in 2006.



Prof. Shenhar’s research interests include studying the self-assembly of polymeric materials and nanoparticles. “If we fundamentally understand how polymeric systems organize at the nanoscale, then we could extend this knowledge to a wide variety of applications that require nanoscale order and periodicity, like advanced optical devices. In biology, it is known that cells respond to nanostructured surfaces; being able to assemble materials into ordered nanoscale structures opens up many opportunities for modifying cells and controlling cellular behavior. Nanoscale ordering has a great future”, says Roy. 
The research in the Shenhar Group focuses on block copolymers – a unique family of self-ordering polymers, which spontaneously create periodic nanoscale structures through phase separation – like oil and water, but much better. “The beauty of block copolymers is the richness of available structures that can be obtained by a simple chemical architecture – two different polymers that are tethered by a covalent block”, says Roy. “Now all you have to do is decide which morphology you desire – alternating layers, cylinders or spheres in a matrix – and what periodicity in the range of 1-300 nm you seek. These decisions then dictate the lengths of the different polymer blocks you aim for in the polymer synthesis. Once you have the material, just heat it up and it will spontaneously form the required nanostructures!”

A major effort in Shenhar’s group research is dedicated to studying the cooperative assembly of polymers and inorganic nanoparticles, especially metallic and semiconductor nano-spheres and nano-rods. “It turns out that the presence of nanoparticles embedded in the block copolymer material influences the overall structure in non-trivial ways”, says Roy. “For example, it is known that adding nanoparticles to block copolymer films causes the polymer domains to orient perpendicular to the substrate because nanoparticles tend to localize at the film surface. Tailoring the chemistry of the nanoparticles to be chemically compatible with the polymer block that prefers to wet the substrate leads to a situation with competing effects – that lead to new morphologies. Moreover, we have found that under these conditions the shape of the nanoparticle has a strong influence on the final structure”.

Currently, much of the group’s research is directed at combining top-down nano-fabrication with the bottom-up, self-assembly of block copolymer – using lithography to create nano-patterned substrates that align the nanoscale polymer domains. “This combination has proven to be more intriguing than the sum of its components, yielding some unexpected results”, says Roy. “There are many uncharted territories to explore in this wide and emerging field. Recently, the industry has started showing interest in our work, which adds another flavor to the basic science we do”, he adds. “Block copolymer research has always been situated in the field of nanoscience, but along with the continuing scientific discoveries and developments, it is now turning into viable nanotechnology, which is very exciting. We have only seen the tip of the iceberg with respect to its impact on materials science, and with it on everyday life”. 

I ask Roy for the challenges he and his group members face during the research. “Working on the borderline between the known and the unknown is always a challenge; systems don’t always behave the way we want or predict” he answers. “There is also a long training period that students have to undergo to be able to perform research in the group, but this is natural for such interdisciplinary fields as polymer science and nanoscience. But all the investment pays off when a student comes back from the nano-center with a gallery of microscopy images that show an interesting trend and a new assembly behavior that boggles our mind”.

“Any success stories you would like to share?” I ask. “Well, our collaboration with the industry has only recently begun, so ‘success’ in the sense of commercialization of knowledge is still on its way. However, every paper that we publish is a success story on its own; a new discovery or a new insight that was revealed, and I’m very proud of each and every one of these successes”, Shenhar says. He highlights the recent discovery that demonstrated the controlled creation of mixed morphologies of block copolymers cast on topographically patterned substrates, and the collaborative work with Prof. Meital Reches from our center and Prof. Hsiao-Hua Yu from the Acadmia Sinica in Taiwan, which he described as a seed for a very interesting development in the utilization of nano-patterned surfaces for cell treatment and modification. 
“All these years, our nano-center has been the center pole of the group’s research”, Roy says. In the unit for nanocharacterization (UNC), Roy’s students are using the scanning electron microscope (SEM) and the atomic force microscope (AFM) to characterize the block copolymer-based nanoscale patterns and nanocomposites. Moreover, the unit for nanofabrication (UNF) is also a major spot for his students; they are mainly fabricating topographic nano-patterned substrates by the electron beam lithography and using all other required equipment to help getting final products like the reactive ion etching and plasma ash systems. Roy adds: “Besides the collection of high-end instruments, our nano-center features an amazing combination of dedicated technical staff and academic groups that work together to advance scientific knowledge. It is a vibrant community – and a very enjoyable one to be working in”.