University Events

Description: Mechanical Engineering (MNE) SEMINAR

DATE:
Friday, November 4, 2022

TIME:
2:00 p.m. - 3:00 p.m.

LOCATION:
Library, Room 426 (LIB-426)

SPEAKER:
Dr. Ruobing Bai, Assistant Professor
Mechanical and Industrial Engineering, Northeastern University

TOPIC:
Photomechanical Coupling in Photoactive Molecular Crystals and Liquid Crystal Elastomers

ABSTRACT:
Some molecules can absorb light of a certain wavelength and change their shape, dissociate, or combine to form new molecules. Photoactive materials made from these molecules are capable of large deformation or mechanical work output upon light illumination, inspiring new applications of photomechanical machines. However, compared to an individual photoactive molecule, existing photoactive materials at the macroscale perform much poorer in their actuation efficiency and work output, severely limiting their application in real scenario. This contrast highlights an urgent research need for mechanistic understanding of photomechanics at the mesoscale (e.g., micrometer) that bridges a nanoscale molecule and a macroscale material. This talk will present our recent progress in such fundamental understanding of mesoscale photomechanical coupling in photoactive molecular crystals and liquid crystal elastomers. Using statistical and continuum theoretical frameworks, we focus on the two-way photomechanical coupling between photoreaction and mechanics. When embedded in a solid, photoactive molecules do not react independently, but behave collectively through various long-range interactions, leading to interesting phenomena including tunable molecular alignment, phase transition, formation of microstructure, instability, and their consequences in the macroscopic material actuation. Further discussed are the critical role of temperature in modulating photomechanical actuation and our latest experimental progress in the synthesis-property relationship of liquid crystal elastomers.

BIO:
Ruobing Bai is an assistant professor in the Department of Mechanical and Industrial Engineering at Northeastern University. He received his BS in Theoretical and Applied Mechanics at Peking University in 2012, and PhD in Engineering Sciences at Harvard University in 2018. He was a postdoctoral fellow in the Department of Mechanical and Civil Engineering at California Institute of Technology from 2018 to 2020. He is the recipient of the Chun-Tsung Scholar endowed by Hui-Chun Chin and Tsung-Dao Lee in Peking University and the Haythornthwaite Research Initiation Award from the Applied Mechanics Division of American Society of Mechanical Engineers. Research in the Bai group aims to combine theory and experiment in areas including solid mechanics, soft active materials, fracture and toughening of materials, adhesion, and sustainable materials, for applications such as soft robotics, human-machine interfaces, and human health.

For more information please contact Dr. Hangjian Ling, MNE Seminar Coordinator (hling1@umassd.edu).

All are welcome.

Students taking MNE-500 are REQUIRED to attend! All other MNE BS and MS students are encouraged to attend.

EAS students are also encouraged to attend.