A photoswitch contains organic photochromic compounds that are excited by direct exposure to light, triggering a mechanical response. / Courtesy of Wikimedia Commons

Javier Read de Alaniz, the chemistry professor and the associate director of the California NanoSystem Institute (CNSI) at UCSB, recently embarked on a new $7.5 million, five-year Multidisciplinary Research Initiative (MURI)-funded project called “Photochemical Materials Systems: From Molecules to Devices.” This new MURI team consists of several scholars from multiple fields and universities. It is led by polymer scientist Ryan Hayward, and the other group members are Christopher Bardeen of UC Riverside, Todd Martinez of Stanford, Read de Alaniz of UC Santa Barbara, physicist Peter Palffy-Muhoray of Kent State and mechanical engineer Kaushik Bhattacharya of CalTech.

This MURI project is in the design stage right now, where Read de Alaniz put forward an idea about developing a new technology that can successfully realize the function of transporting work without relying on the physical devices to carry the energy. Talking about the overall planning for the group, Read de Alaniz said, “The overarching goal of the project at this stage is to bring together a team with a wide variety of backgrounds to rethink how light-responsive materials are designed and fabricated.”

He also talks about the hopeful short-term outcome of the research, in which there might be a set of design principles that can be used to create the optimal light-responsive material, and most likely there will not be one material for each envisioned application.

The key to this new technology is to find the best suitable photoresponsive materials. In the research of MURI team, they try to get the access to such materials through the knowledge from different academic areas. In Read de Alaniz’s explanation, this project will merge theory, modeling and simulations with synthesis, processing and characterization of new materials and systems across length-scales ranging from single molecules to bulk materials, culminating in the development of working light-driven devices. Quantum mechanical modeling will be an important way to find the ideal photoresponsive materials, and it will provide the basis for the synthesis of new classes of light-responsive compounds on the molecular scale, which will be paired with new approaches to self-assembly and material architecture on the mesoscale and systematic characterization of photoresponses on the macroscale, providing an integrated roadmap for the effective design of photomechanical materials.

As one of the main members in this MURI project and a synthetic chemist, Read de Alaniz describes his role is to help design and synthesize new photochromic material and device novel approaches to assemble the material using material architectures that maximize photoresponses on the macroscale.

Photoswitch is one of the important parts in this MURI project, and donor-acceptor Stenhouse adducts (DASAs) are very significant materials that were discovered by Read de Alaniz and his team. In his introduction, DASAs feature several important advantages compared to other photochromic material, including being visible to near-infrared light responsive, as many photochromic materials require UV light which is damaging to cells and materials, and having modular synthetic architecture, as this enables them to be readily incorporated into material for specific applications.

They are also highly colored in their stable form. This means they can be used for many sensing applications where the naked eye can be used to visualize the response.

Finally, they have negative photochromism. This means they convert from a colored state to a colorless state upon treatment with light. This feature is important because it enables light penetration into the bulk of the material which is necessary to drive a photoresponse throughout the material.

Currently, there are many challenges that occur during the process of developing new materials because it is a totally new idea and nobody knows the design rules or what is actually possible.

As Read de Alaniz said, “There is debate around what is the ideal photoswitch, what type of material is best suited for generating a photomechanical response, what are the best metrics to use so that we can compare different systems. While there has been lots of work on many of the individual parts, we are basically starting with a blank slate. This is one of the attractive aspects of this project.”

Even though it is a very brand new idea in the field of synthesis materials, the entire MURI team is still optimistic toward this optical light-responsive material due to the strong financial support, which is a $7.5 million dollar fund for three years with the possibility to extend to five years. Read de Alaniz also considers that it might take 15 years to take the photoresponsive materials into specific applications.

Certainly, this MURI project has a large number of advantages for energy conservation. It is also a tremendous challenge for Javier and his team. However, with the close cooperation between scholars in the team and full support from CNSI and MURI, they will finally get through the siege and bring the new photoresponsive materials in the future.