Investigating the self-healing properties of biological gels Featured

    Summer Scholar Lucia Brunel interns under Profs. McKinley and Ribbeck to understand the self-healing properties of mucus and other biological gels. 

    Summer Scholar Lucia Brunel 8896 DP Web
    2017 MPC-CMSE Summer Scholar Lucia Brunel examines the self-healing properties of biological gels, such as mucus, using an optical tweezer active microrheology setup. Rheology is the study of how materials flow or respond to deformation. The goal of the project is to investigate the dynamics of the self-healing process of mucus and other biological gels. Photo, Denis Paiste, Materials Processing Center

    Biological gels such as mucus and saliva serve many important roles in the body, from acting as barriers to infection to lubricating the eyes and oral cavity. 2017 MPC-CMSE Summer Scholar Lucia Brunel is working on a joint project under Professors Gareth McKinley and Katharina Ribbeck.

    “I have a background in traditional polymer science, but I’m really interested in applications to biological systems,” says Brunel, a rising senior at Northwestern University studying chemical and biological engineering. “My project is to investigate the unique self-healing capability that some biological gels have, so I’ve been learning a lot about how to characterize the properties of these biological gels as they heal after damage or deformation.”

    MIT graduate student Caroline Wagner, whose doctoral studies focus on investigating the mechanical properties of biological gels, is supervising Brunel’s work in the MIT Bioinstrumentation Lab. “One thing that's still really eluding us is the exact biophysical mechanism for how biological gels self-heal, and the time scale over which this happens.” Wagner says, “For instance, mucus repairs itself very quickly on a regular basis, whether after permitting the passage of sperm or following an event such as a cough or a sneeze, but translating this ability to synthetic materials remains a huge challenge. So when Lucia wanted to join the lab, we thought that focusing on the dynamics of self-healing in biological gels could form the basis for a really interesting summer project.”

    Brunel adds that “The design of biomimetic gels comes from an understanding of the properties of the real biological gels, so before making synthetic materials that self-heal, we have to know how biological gels do that. A better understanding of the self-healing abilities of certain biological gels could ultimately lead to the creation of self-healing synthetic materials for use in implantable devices, scaffolds for tissue engineering, or prosthetics, which would be incredible.”

    During her summer internship, Brunel has been learning about the technique of rheology, which is the study of how materials flow or respond to deformation. “Rheology is really useful for being able to characterize materials, especially complex fluids like biological gels that have both a viscous component and an elastic component and are somewhere between a liquid and solid,” Brunel says. “I've been doing both micro rheology to tell how the material deforms and recovers on the microscopic scale, as well as macro rheology to understand the material’s bulk mechanical properties. These two techniques complement each other to give us a more comprehensive idea of the material’s response to deformation,” she says.

    “The goal of my project is to develop experiments to quantitatively characterize the time scale of the self-healing process of biological gels, especially on the microscopic scale,” Brunel explains. “To do so, I’m using the technique of active micro rheology with optical tweezers. Optical tweezers use a laser beam to trap micron-sized beads in a sample, and once a bead is trapped, it can be moved through the sample in a controlled manner. By dragging the bead around, we deform the material and then can see how the drag force on the bead changes over time as the material recovers. If the force required to move the bead through the material is lower than it was before the deformation, the material is still damaged, but if the resistance is the same, then the material has repaired itself. We can test these experiments on different time scales to get a more quantitative measurement of the self-healing process of these special biological gels.”

    Brunel’s internship is supported in part by NSF’s Materials Research Science and Engineering Centers program [grant DMR-14-19807]. Participants in the Research Experience for Undergraduates, co-sponsored by the Materials Processing Center and the Center for Materials Science and Engineering, will present their results at a poster session during the last week of the program. The program runs from June 15, 2017, to August 5, 2017, on the MIT campus in Cambridge, Mass.

    – Denis Paiste, Materials Processing Center
    July 31, 2017