Student(s): Leela Deshpande
Project: Measuring the Surface and Viscoelastic Properties of Treated Hair
Advisor(s): James Gilchrist
Abstract
The global hair care industry, valued at over $90 billion annually, faces challenges in quantifying how cosmetic treatments alter the physical properties of hair fibers. Chemical bleaching, in particular, is of interest, as hydrogen peroxide penetrates the hair shaft and disrupts structural components such as melanin and the cuticle. While these changes are visually apparent, their impact on the mechanical and viscoelastic behavior of hair remains unclear. In this study, a torsional pendulum technique was used to measure the viscoelastic response of individual human hair fibers. Single strands were segmented and treated with varying concentrations of hydrogen peroxide, alongside untreated controls. Oscillatory motion was tracked through visual imaging and the logarithmic decay was extracted. Additionally, the Fourier transform analysis was used to extract resonant frequency and damping behavior, allowing for calculation of the elastic (G′) and viscous (G″) moduli. Despite visible lightening of treated fibers, results suggest that there remain minimal changes in viscoelastic properties across all peroxide concentrations. Both G′ and G″ remained relatively consistent, suggesting that the internal keratin structure governing mechanical behavior is largely unaffected by bleaching. These findings highlight the mechanical resilience of hair fibers and suggest that cosmetic damage does not necessarily correlate with significant changes in bulk viscoelastic performance.
About Leela Deshpande
Major: Chemical and Biomolecular Engineering
Leela Deshpande is a junior chemical engineering undergraduate student at Lehigh University with an interest in cosmetic science. She joined Professor James Gilchrist’s lab in February 2025 and conducted research as a Clare Boothe Luce Scholar during Summer 2025. Her work focuses on measuring the viscoelastic properties of human hair fibers using a torsional pendulum, with particular emphasis on understanding the mechanical effects of hydrogen peroxide treatments. Through this research, she has explored how chemical modifications influence the structural and mechanical behavior of hair. Following graduation, Leela hopes to pursue a career in the cosmetic industry, focusing on product development and formulation. Outside of research, Leela serves as an Orientation Coordinator through Lehigh’s Office of First-Year Experience, where she facilitates weekly trainings for incoming orientation leaders and supports the transition of new students to campus.