(2fa) Rheology-Guided Design and Understanding of Soft Materials

Understanding of and control over a material’s mechanical properties is crucial to consistently achieving its desired function and performance. We encounter soft materials constantly in our daily lives in the forms of gels, foams, plastics, and living organisms. Soft matter mechanics remains an exciting area of research due to its interdisciplinary nature and its applicability to all facets of the human existence. Materials and systems of particular interest to me are those which undergo macroscopic phase changes due to microstructural rearrangement, for example, solution-to-gel transitions occurring during polymer crosslinking, complex coacervation leading to liquid-liquid phase separation, and reversible shear jamming of suspensions. My research group will use insights gained from experimental rheology to design novel soft materials and further our understanding of soft material behavior.

Doctoral research: advised by Dr. Saad Khan (Chemical and Biomolecular Engineering), North Carolina State University

My doctoral research centered around applying rheological measurement techniques to complex and dynamic soft materials. During my PhD I have worked on projects involving a variety of materials, including photocurable polymer nanocomposites [1-2] and drug delivery gels [3]; however, my efforts were concentrated in the two projects listed below.

In my first project, I quantified in vivo enzymatic degradation of uterine fibroids to evaluate the effectiveness of novel injectable collagenase treatments on softening tissues [4]. The treatments included co-injection of a thermoresponsive, hydrolyzable NIPAM-based copolymer which gels at physiological temperatures to reduce collagenase diffusion from the injection site, allowing for sustained enzyme activity. We demonstrated that these injectable treatments can significantly reduce tissue modulus and increase tissue viscoelasticity and related the mechanical response (rheology) to the physiological response (histology) to gain a more complete understanding of treatment effects on soft tissues.

In my second project, I demonstrated how ultraviolet (UV) light affects coordinated ionic liquids (ILs) containing reactive vinyl groups, which provide a tunable medium for bulk polymerization and network formation [5]. Rheology was used to monitor the in situ photopolymerization of coordinated ILs containing varying vinylimidazoles and metal bistriflimide salts. At intermediate salt concentrations, coordinated ILs became gels after UV light exposure due to coordination-induced physical crosslinking between growing polymer chains. We also observed how parameters such as UV light intensity, exposure time, and molecular architecture affected material response to demonstrate the tunability of this class of materials.

Postdoctoral research: advised by Dr. Arezoo Ardekani (Mechanical Engineering) and Dr. Kendra Erk (Materials Engineering), Purdue University

As a Lillian Gilbreth Postdoctoral Scholar at Purdue University, I am currently studying the rheology of concentrated particle suspensions. For my main project, I am examining discontinuous shear thickening in 3D-printable polymer-ceramic suspensions and seeking to understand how polymer selection and content affects the rheology, onset of shear thickening, and printability. I am also collaborating with graduate students on projects relating to the rheology of fiber suspensions, corn stover biomass, and mammalian tissues.

Teaching Interests

Due to my education and experience in chemical engineering, I am qualified to teach all core undergraduate and graduate chemical engineering courses. Specific courses I would be excited to teach include transport phenomena, heat and mass transfer, chemical reaction engineering, material balances, and polymer science. I am also interested in developing an advanced undergraduate/graduate course on soft matter mechanics which combines principles of soft matter physics and rheology with a review of experimental mechanical characterization techniques. I co-taught Transport Processes I as a Mentored Teaching Fellow during my PhD during which I taught lectures, wrote exam problems, and introduced MATLAB to the course curriculum through the creation of an in-class tutorial and a series of homework problems. That experience taught me the importance of developing alternative explanations of concepts in case students have a difficult time understanding and provided me with valuable feedback from both the students and my faculty and peer mentors.

As an educator, I seek to cultivate technical proficiency and problem-solving skills to prepare students to become leaders in the engineering workforce. It is critical for students to realize the importance of the material they learn in the classroom and understand how they must apply that knowledge to be successful in their careers. For example, students need to understand how to calculate frictional energy losses in pipes not just to get a passing grade in their fluids class, but so that they will be able to select the appropriate pump for a new cooling system at a potential future job at a power plant. In addition to emphasizing the industrial applicability of their coursework, it is important to give students a strong theoretical foundation to prepare them for success in graduate school. Walking students through mathematical derivations, rather than jumping ahead to a formula they can plug numbers into, can help them better understand the assumptions behind that equation and therefore its limitations. I will intentionally design my course websites to promote accessibility and cultivate a classroom culture of mutual respect and inclusivity. Finally, I believe that research is most effectively and enjoyably conducted in collaboration, and I aspire for my research group to be a place where students from diverse backgrounds can feel comfortable contributing their ideas and receiving feedback and mentorship from each other.

Selected Publications (* denotes equal contributions):

1. Corder, R. D.*; Adhikari, P.*, Burroughs, M. C.; Rojas, O. J.; Khan, S. A. “Cellulose Nanocrystals for Gelation and Percolation-Induced Reinforcement of a Photocurable Poly(vinyl alcohol) Derivative.” Soft Matter 2020, 16 (37), 8602-8611.

2. Corder, R. D.*; Tilly, J. C.*; Ingram, W. F.; Roh, S.; Spontak, R.J.; Khan, S. A. “Rheology of UV-Curable Polymer Nanocomposites Based on Poly(dimethyl siloxane) and Zirconia Nanoparticles: Role of Reactive vs. Passive Fillers.” ACS Appl. Polym. Mater. 2020, 2 (2), 394-403.

3. Wang, J.; Ye, Y.; Yu, J.; Kahkoska, A. R.; Zhang, X.; Wang, C.; Sun, W.; Corder, R. D.; Chen, Z.; Khan, S. A.; Gu, Z. “Core-Shell Microneedle Gel for Self-Regulated Insulin Delivery.” ACS Nano 2018, 12 (3), 3466-2473.

4. Corder, R. D.; Dudick, S. C.; Bara, J. E.; Khan, S. A. “Photorheology and Gelation during Polymerization of Coordinated Ionic Liquids.” ACS Appl. Polym. Mater. 2020, 2 (6), 2397-2405.

5. Corder, R. D.*; Gadi, S. V.*; Vachieri, R. B.; Jayes, F. L.; Cullen, J. M.; Khan, S. A.; Taylor, D. K. “Using Rheology to Quantify the Effects of Localized Collagenase Treatments on Uterine Fibroid Digestion.” Acta Biomater. 2021, 134, 443-452.