Garrell enrolled in the PhD program in macromolecular science and engineering at the University of Michigan, where she worked with Samuel Krimm to develop surface-enhanced Raman spectroscopy as a technique for characterizing adsorption at liquid-metal interfaces.

While at UCLA, Garrell co-led a multi-year project in partnership with UC Davis and funded by the Andrew G. Mellon Foundation, to advance holistic admissions in humanities and social science doctoral programs.

Through grants from the National Science Foundation (NSF IGERT Materials Creation Training Program, NSF AGEP California Alliance) Garrell advanced interdisciplinary training and developed longitudinal and interinstitutional mentoring networks that support the advancement of diverse STEM scholars into faculty careers.

Garrell's research has centered on physical phenomena at liquid-solid interfaces, including adsorption, adhesion, wetting and electromechanical actuation.

She pioneered surface-enhanced Raman spectroscopy as a tool for characterizing the behavior of biomolecules at liquid-metal interfaces, determined structures and stabilities of self-assembled monolayers, and enabled widespread use of SERS in sensors and diagnostics.

Garrell also made significant advances in droplet microfluidics, showed how electric fields can be used to manipulate liquids and perform reactions on-chip, and developed multi-step processing of biological samples for MALDI-MS proteomics analysis and preparing three-dimensional cell cultures for in situ assays.

Garrell's research on mussel adhesive protein was featured in two television documentaries: Biomimicry (written by Janine Benyus, directed by Paul Lang, produced by Michael Allder for the Canadian Broadcasting Corporation, and based in part on the book Biomimicry, Innovation Inspired by Nature, by Janine Benyus) and The History of Glue documentary episode in the Modern Marvels Series, History Channel (Actuality Productions, ©2005).