Charlotte Rodriguez spent her summer at UC Santa Barbara investigating nitinol — a nickel-titanium alloy widely used in biomedical devices, such as self-expanding heart stents. Guided by Samantha Daly, a mechanical engineering professor, and mentored by PhD candidate Andrew Christison from the Daly group, Rodriguez worked to address one of the material’s most pressing challenges — its fatigue life, which relates to the number of cycles of stress it can withstand before failure.
Rodriguez conducted her research through the Future Leaders in Advanced Materials (FLAM) internship program offered by the Materials Research Laboratory (MRL). With access to the facilities, including the machine testing center, she completed four tests, each time gradually increasing the material’s prestrain, which is the inherent strain of a material before any external stress is applied. The results showed that higher prestrain reduced strain localization, offering valuable clues as to how nitinol responds under repeated stress. She explained that strain localization happens when stress or deformation in a material concentrates in a specific region instead of spreading out evenly. Over time, these concentrated stress spots weaken the material, making it more likely to crack or fail. Rodriguez noted, “Understanding the fatigue behavior of nitinol is critical to creating biomedical devices that have long-term reliability.”
Charlotte Rodriguez presenting her research at MRL's Summer Poster Colloquium
A mechanical engineering student from Cal Poly Pomona, Rodriguez was one of the twenty-four undergraduate students who showcased the results of their summer internship at the MRL Summer Poster Colloquium, held at the Engineering Science Building on August 15. “The annual event provides a dynamic forum for students to present their research, exchange ideas, and network with faculty, peers, and researchers across disciplines in a diverse and supportive environment,” said MRL education director, Julie Standish.
The colloquium stands as a highlight of the internship experience, providing undergraduate students their first chance to present as researchers — articulating discoveries, defending methods, and engaging in scientific dialog with faculty and peers. The event not only validates the students’ hard work, but also builds confidence, scientific communication skills, and a sense of belonging in the research community.
The MRL runs multiple internship programs, including (FLAM), California Alliance for Minority Participation (CAMP), Cooperative International Science and Engineering Internships (CISEI), and the Partnership for Research and Education in Materials (PREM) (with Jackson State University in Mississippi).
For Steven Rangel-Garcia, a third-year biology major at UCSB, the CAMP internship program was more than a summer opportunity. Working under the mentorship of Javier Reid de Alaniz, a professor in the department of chemistry and biochemistry, and doctoral candidate Anwesha Guha from the Read de Alaniz group, Rangel-Garcia explored the photomechanical properties of diarylethene crystals, which are photo-switch molecules, meaning they can change their form and properties when exposed to different types of light and generate mechanical work. “Unlike traditional actuators, which rely on oil or electricity, these crystals can be actuated with light alone,” Rangel-Garcia explained.
Though at a nascent stage, the project carries exciting possibilities. The possible applications of DAE molecules and DAE-based crystals include light-driven actuators, micro-mechanical devices, and drug delivery among many others. One demonstrated use is in photochromic or photo-switch tattoos — designs that appear or disappear under UV light. Rangel-Garcia explained, “Positive photochrome tattoos use DAE-coated microparticles that change from colored to colorless under UV light. They act as warning indicators, showing when someone has had too much sun exposure and help to prevent skin damage. Negative photochrome tattoos turn colored under UV light but remain invisible in normal light, making them useful for reversible, non-invasive aesthetic designs.
The internship turned out to be a big learning experience for Rangel-Garcia, who had always wanted to pursue research. “To me, being a scholar means being a researcher,” he said. “This project let me dip my toes into the real world of research — not just working in the lab, but seeing how ideas develop and take shape. What excites me most is the possibility that this work could lead to something meaningful, something that truly helps people, and that’s the real beauty of research.”
Carolyn Hanrahan, a chemical engineering student from the University of Wisconsin, described being accepted for a FLAM internship at UCSB as a thrilling opportunity that brought growth and connections. Having never left Wisconsin before, she welcomed the chance to move to California for nine weeks and adapt to a new environment. “I thought I might be homesick,” she said, “but I met awesome people, and we all lived together in student housing as a cohort. It was great.”
Carolyn Hanrahan presenting her investigation of mechanical properties of PEGDA hydrogels with covalently bonded particles.
Hanrahan’s research focused on finding ways to enhance the strength of hydrogels, which are cross-linked polymer networks that absorb and retain water and have application in many fields, but are also, as she said, “often weak and brittle.”
At UCSB, she worked under the guidance of mechanical engineering professor Megan Valentine, and was advised by two postdoctoral mentors, Antonio Garcia and Hao Dong from the Valentine research group, who provided valuable feedback as she analyzed preliminary data and refined her experiments. Hanharan described their support as a key part of her progress in the lab.
She also cited the networking that occurred as part of her internship as a major highlight. She noted that her LinkedIn connections doubled during her time at UCSB. Weekly meetings with interns from FLAM and international programs provided her with opportunities to share feedback and to learn from a diverse community of researchers. Reflecting on the experience, she said, “It taught me how to collaborate, troubleshoot independently, and thrive as part of a research team, while gaining confidence and community in a new environment.”
