Monthly Tutorial: Claribel Acevedo Velez

Date: September 8, 2025 @ 12-1pm EDT / AST

Location: Amy Gutmann Hall (3317 Chestnut St), Room 414, and via Zoom (email Annie for link).

Speaker: Claribel Acevedo Velez, Professor, Chemical and Engineering, UPR-Mayagüez

Title: Liquid Crystal Emulsions Stabilized by Nanoparticles: New Approaches to Design Droplet-based Sensors for the Optical Detection of Amphiphilic Analytes

Lunch will be provided for in-person attendees at Penn (please bring your own drinks!)

Abstract: Micrometer-sized droplets of thermotropic liquid crystals (LCs) dispersed in water (e.g., LC-in-water emulsions) provide versatile platforms for the design of droplet-based sensors capable of detecting and reporting the presence of amphiphilic analytes, including surfactants, biosurfactants, phospholipids, and endotoxins in aqueous environments. However, the practical application of LC-in-water emulsions has been limited by their poor colloidal stability, as bare LC droplets readily coalesce within hours of preparation. This presentation will describe our recent efforts aimed at designing LC droplet-based sensors with (i) improved colloidal stability and (ii) tunable sensitivity and selectivity to aqueous analytes. Our approach consists of preparing LC emulsions stabilized by surface-modified nanoparticles adsorbed at the LC–water interface. This strategy prevents droplet coalescence and yields emulsions that remain colloidally stable for at least three months to one year. These nanoparticle-stabilized LC droplets retain their responsiveness to amphiphilic analytes, undergoing characteristic bipolar-to-radial LC ordering transitions observable in real time under polarized light microscopy. Moreover, by varying the nanoparticle system used for stabilization, we demonstrate the ability to tune the sensitivity and potential selectivity of these droplets toward different classes of analytes. Overall, these results highlight nanoparticle-stabilized LC emulsions as promising and tunable platforms for the development of droplet-based biosensors with improved shelf-life and enhanced practical utility for chemical and biological detection in aqueous environments.

Speaker Bio: Dr. Claribel Acevedo-Velez is an Associate Professor in the Department of Chemical Engineering at the University of Puerto Rico-Mayagüez (UPRM) and Director of the UPR-UW PREM: Center for Advancing Research and Training for STEM Success. She also serves as Associate Director of Education of the NSF Artificial Intelligence-driven RNA BioFoundry (NSF AIRFoundry) and Director of the UPRM Center for Nanostructure Characterization (CeNaC). Her research explores colloids, liquid crystals, and surface and interface science. A key focus of her lab is the development of liquid crystal-based sensors for rapid, point-of-use detection of chemical and biological analytes. Before joining UPRM in 2017, Dr. Acevedo-Velez was a scientist and project leader at The Dow Chemical Company (2012–2017), specializing in surfactant formulation for applications ranging from crude oil recovery to consumer products. She integrates her industry and academic experience to mentor students, leading a research group of both graduate and undergraduate researchers. Committed to STEM education and outreach, she actively encourages students at all levels (K-12 to graduate) to pursue careers in science and engineering.