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Mechanical and Civil Engineering Seminar

Thursday, January 20, 2022
11:00am to 12:00pm
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Gates-Thomas 135
Nonlinear Dynamics of Soft Filaments
Neda Maghsoodi, Ph.D., Postdoctoral Scholar, Mechanical and Civil Engineering, California Institute of Technology,

Mechanical and Civil Engineering Seminar Series

Title: Nonlinear Dynamics of Soft Filaments

Filaments of soft materials such as rubber and biopolymers can easily undergo large complex deformations under external stimuli. Soft filaments offer exciting applications in engineering, life science, and medicine since their nonlinear conformational changes can be harnessed for robust functional mechanisms. Understanding the dynamics of soft filaments is fundamental to advancing future engineering and medical applications. In this talk, I present analytical models for two fascinating soft filaments that function in the nonlinear regime; 1) protein filaments forming the contractile injection machinery of the virus bacteriophage T4, and 2) photoactivated liquid crystal elastomeric (LCEs) filaments proposed for future soft robotics. I present dynamic models for both filaments based on continuum rod theory to predict their dynamical nonlinear behaviors. For context, bacteriophage T4 is an intriguing nano-scale injection machine that infects the bacterium E. coli (its host) by rupturing the cell membrane and then injecting its genome into the host cell. The injection process is initiated when the injection machine, composed of protein filaments, undergoes a nonlinear conformational change to drive the T4 needle into the host. Photomechanical LCEs are engineered, light-sensitive polymers that undergo large reversible deformations under illumination. For these systems, I show how phage T4 exploits large deformations of the protein filaments for efficient DNA injection, and how one can harness nonlinear deformations of LCE filament to generate periodic motions under steady illumination. These findings have significant implications for designing future soft material devices and bio-inspired soft robotics.

Bio: Neda Maghsoodi is a postdoctoral scholar at the California Institute of Technology (CalTech). Neda received her Ph.D. in Mechanical Engineering in 2019 and her M.Sc. in Biomedical Engineering in 2017 from the University of Michigan-Ann Arbor. Prior to joining the University of Michigan, she earned her B.Sc. and M.Sc. both in Mechanical Engineering from Iran. Neda's research lies at the interface of applied mechanics, materials science, and biology and develops theoretical models to elucidate nonlinear dynamics of soft filaments at a broad range of time- and length-scales. In her academic career, Neda was named a "Rising Star" in Mechanical Engineering by UC-Berkeley (2020), received the "Best Paper" award in the ASME International Conference on Micro- and Nanosystems, and received the "Best B.Sc. Thesis" award of the year from the Iranian Society of Acoustics and Vibration. The novelty and significance of her research have been featured in Biophysical Journal as the "New and Notable Article" and in several news outlets.

NOTE: At this time, in-person Mechanical and Civil Engineering Lectures are open to all Caltech students/staff/faculty/visitors with a valid Caltech ID. Outside community members are welcome to join our online webinar.

Please click the link below to join the webinar:

Passcode: 012488

For more information, please contact Jenni Campbell by email at [email protected] or visit