Paper Number
AD12 

Session
Active and Directed Systems

Title
Programming stiffness change in soft materials

Presentation Date and Time
October 24, 2019 (Thursday) 9:30

Track / Room
Track 5 / Room 306A

Authors (Click on name to view author profile)

  1. Chaudhary, Gaurav (University of Illinois at Urbana-Champaign)
  2. Ghosh, Ashesh (University of Illinois at Urbana-Champaign, Department of Chemistry)
  3. Bharadwaj, Ashwin (Nike Inc.)
  4. Kang, Jin Gu (Korea Institute of Science and Technology)
  5. Braun, Paul (University of Illinois at Urbana-Champaign)
  6. Schweizer, Kenneth S. (University of Illinois at Urbana-Champaign, Department of Materials Science and Engineering)
  7. Ewoldt, Randy H. (University of Illinois at Urbana-Champaign, Department of Mechanical Science and Engineering)

Author and Affiliation Lines (in printed abstract book)
Gaurav Chaudhary1, Ashesh Ghosh1, Ashwin Bharadwaj2, Jin Gu Kang3, Paul Braun1, Kenneth S. Schweizer1, and Randy H. Ewoldt1
1University of Illinois at Urbana-Champaign, Urbana, IL 61801; 2Nike Inc., Portland, OR; 3Korea Institute of Science and Technology, Seoul, Republic of Korea

Speaker / Presenter 
Ewoldt, Randy H.

Text of Abstract
We demonstrate new paradigms in designing stiffness changing soft materials. Our approach involves combining a semiflexible biopolymer network of fibrin with stimuli-responsive particles, either thermoresponsive microgels of poly(N-isopropylacrylamide) (pNIPAM)[1] or magnetically active iron particles[2]. When exposed to an external stimulus of thermal excitation or magnetic field, the interactions between the embedded particles and fibrin network lead to an unprecedented increase in stiffness by up to 100 times. We hypothesize that the stimuli responsive particles induce local stress in the biopolymer matrix which intrinsically stiffens under stress. For the thermoresponive composite, the drastic deswelling of the microgels deform fibrin filaments, thus leading to stiffening. For the magnetoresponsive composite, the interaction between magnetic dipoles plays an analogous role. Phenomenological models are developed that quantify these hypotheses. The derived predictions are consistent with the experimental data, providing foundational understanding for how to control and engineer dramatic stiffening in these material systems.

[1] Chaudhary, G., A. Ghosh, N. A. Bharadwaj, J. G. Kang, P. V. Braun, K. S. Schweizer, and R. H. Ewoldt, “Thermoresponsive stiffening with microgel particles in a semiflexible fibrin network,” Macromolecules, 52 (8), 3029-3041 (2019). http://doi.org/10.1021/acs.macromol.9b00124
[2] Chaudhary, G., Ph.D. Thesis, University of Illinois at Urbana-Champaign (2019)