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Mechanisms of local stress sensing in multifunctional polymer films using fluorescent tetrapod nanocrystals

United States Patent Application

View the Complete Application at the US Patent & Trademark Office
Lawrence Berkeley National Laboratory - Visit the Technology Transfer and Intellectual Property Management Department Website
Nanoscale stress-sensing can be used across fields ranging from detection of incipient cracks in structural mechanics to monitoring forces in biological tissues. We demonstrate how tetrapod quantum dots (tQDs) embedded in block-copolymers act as sensors of tensile/compressive stress. Remarkably, tQDs can detect their own composite dispersion and mechanical properties, with a switch in optomechanical response when tQDs are in direct contact. Using experimental characterizations, atomistic simulations and finite-element analyses, we show that under tensile stress, densely-packed tQDs exhibit a photoluminescence peak shifted to higher energies ("blue-shift") due to volumetric compressive stress in their core; loosely-packed tQDs exhibit a peak shifted to lower energies ("red-shift") from tensile stress in the core. The stress-shifts result from the tQD's unique branched morphology in which the CdS arms act as antennas that amplify the stress in the CdSe core. Our nanocomposites exhibit excellent cyclability and scalability with no degraded properties of the host polymer. Colloidal tQDs allow sensing in many materials to potentially enable auto-responsive, smart structural nanocomposites that self-predict impending fracture.
Raja, Shilpa N. (Berkeley, CA), Zherebetskky, Danylo (Walnut Creek, CA), Wu, Siva (Berkeley, CA), Ercius, Peter (Oakland, CA), Olson, Andrew C.K. (San Francisco, CA), Alivisatos, Paul (Berkeley, CA), Ritchie, Robert O. (Berkeley, CA)
The Regents of the University of California (Oakland CA)
15/ 607,158
May 26, 2017
STATEMENT OF GOVERNMENTAL SUPPORT [0002] The invention described and claimed herein was made in part utilizing funds supplied by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231 between the U.S. Department of Energy and the Regents of the University of California for the management and operation of the Lawrence Berkeley National Laboratory. The government has certain rights in this invention.