Research Team from Penn and Duke Design Stress Sensor that Changes Color

It is truly highly beneficial to get a warning when a structural system is on the brink of failure but when that system is of nano-scale size, it is highly challenging. However, researchers have developed a molecular design, which would produce a warning signal by way of a simple color change.

The study was carried out by University of Penn’s Professor Daniel Hammer and a team consisting of graduate students from Penn and Duke, along with Professor Ivan Dmochowski and Professor Michael Therien from Duke.

They used polymersomes, which are artificially developed capsules that include a molecular payload and porphyrins, which are pigments occurring naturally. Graduate students, Liao and Kamat had developed a theory involving the membrane of the polymersomes being embedded with light emitting porphyrins for acting like stress sensors. The researchers from Penn then worked with the Therien lab for designing such a structure. When light was shone on the polymersomes, the porphyrins inside absorbed the light and then gave them out at a particular wavelength or color.

Prof Hammer revealed that the light emission could be modulated and if stress is applied on the confined setting, the porphyrin’s configuration would change and an optical release happens, which comes as a straight measurement of the stress in the environment. By subjecting the polymersomes to various controlled stresses such as heat and tension, and then measuring the color changes, they were able to calibrate the polymersomes by computers. This would be of great benefit in medicine especially in avant-garde pharmaceutical techniques which are already using molecular technology, such as the monitoring of drug delivery. The researchers are also planning to apply the same stress labeling technique on natural tissues. One more application would be using these dyes by directly including them in the cellular membrane for knowing the stress levels inside.