Pulling with jelly: measuring gel forcefulness

M2 Internship proposal

Laboratoire Sciences et Ingénierie de la Matière Molle, (SIMM)

Address: ESPCI, 10 Rue Vauquelin 75005 Paris

Head: Etienne Barthel

Supervisors: Alba MARCELLAN, Shelby HUTCHENS

Contact : ;

Internship period : min. 5 months and max. 6 months not earlier than January, 27th 2025.

Overview

Leveraging the simple act of changing volume, so called ‘active materials’ have been used in to drive motion and shape change in a wide range of applications. Within the past decades, hydrogels have emerged as a particularly promising active material for environmental and medical applications. As their name suggests, hydrogels are comprised primarily of water, but exhibit the properties of a solid due to their 3D cross-linked polymer network. Hydrogels are well known for their swelling properties, however advances in polymer network chemistries have created responsive solids that can swell and deswell in response to environmental cues including pH, salt concentration, and temperature. While significant efforts have been made to characterize the time dependence and forcefulness of the swelling response, studies of deswelling have been limited to stress-free environments. This is unfortunate as hydrogels are known to increase in stiffness during syneresis (deswelling), suggesting a potential for forceful tensile interactions with the surrounding environment. Understanding the mechanism and limitations of such forceful interactions is important for medical applications seeking to leverage responsive hydrogels for regulating a tissue’s mechanical microenvironment, e.g., during healing.

Project approach

Marcellan has developed robust and responsive hydrogel architectures with self-healing properties and, critically, the ability to readily and strongly adhere to a wide range of surfaces. This combination of characteristics facilitates fabrication of highly tunable mechanical environments for the controlled exploration of loaded hydrogel syneresis.

Figure. Schematic depicting hydrogel syneresis under typical conditions (left) in contrast to action under potential loading scenarios (right).

For this project, the intern will participate in gel preparation (gelatin gels) and synthesis (copolymerization of monomer and cross-linker) and mechanical characterization. The candidate will receive training in synthesis, then explore creative fabrication approaches for generating interesting and insightful mechanical loading conditions for the gels. The candidate will employ quantitative optical imaging approaches to document time and load-dependent responses.
The candidate will have the opportunity of being supervised by researchers with complementary expertise: one researcher at SIMM (Marcellan) and one visiting researcher (Hutchens), at SIMM for the project duration, but with her home institution in the Mechanical Science and Engineering Department at the University of Illinois Urbana-Champaign.

Techniques

The project will be comprised of the following activities.
a) Gels of varying geometry and swelling state will be prepared and synthesized. Gelatin A (positively charged) and gelatin B (uncharged) were explored first. Then, synthetic gels will be investigated by tuning the cross-linker density.
b) The deswelling response of the gels under controlled physico-chemical environment (chemical potential) and mechanical environments will be monitored over time.
c) Analysis of the interaction between gel geometry, deswelling driving force, and mechanical boundary conditions will be made.

References

A. Kataruka and S. B. Hutchens, “Swelling of a non-vascular-plant-inspired soft composite,” Matter, vol. 4, no. 12, pp. 3991–4005, 2021, doi: 10.1016/j.matt.2021.10.015.
S. Rose, A. Prevoteau, P. Elziere, D. Hourdet, A. Marcellan, L. Leibler, “Nanoparticle solutions as adhesives for gels and biological tissues”, Nature (2014) doi: 10.1038/nature12806
G. Theocharidis et al., “A strain-programmed patch for the healing of diabetic wounds,” Nat. Biomed. Eng, vol. 6, no. 10, pp. 1118–1133, Jul. 2022, doi: 10.1038/s41551-022-00905-2.
S. M. Hashmi and E. R. Dufresne, “Mechanical properties of individual microgel particles through the deswelling transition,” Soft Matter, vol. 5, no. 19, p. 3682, 2009, doi: 10.1039/b906051k.
J. F. Louf, N. B. Lu, M. G. O’Connell, H. J. Cho, and S. S. Datta, “Under pressure: Hydrogel swelling in a granular medium,” SCIENCE ADVANCES, vol. 7, no. 7, 2021, doi: 10.1126/sciadv.abd271.

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23/10/2024