University of California

Robert O Ritchie

James Nasiatka

Alastair A MacDowell

Sanjay Govindjee

Peter Ercius

Andrew C K Olson

Hrishikesh A Bale

Abdel Haboub

Danylo Zherebetskyy

Shilpa N Raja

Siva Wu

Paul Alvisatos

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.

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

This disclosure provides systems, methods, and apparatus related to the high temperature mechanical testing of materials. In one aspect, a method includes providing an apparatus. The apparatus may include a chamber. The chamber may comprise a top portion and a bottom portion, with the top portion and the bottom portion each joined to a window material. A first cooled fixture and a second cooled fixture may be mounted to the chamber and configured to hold the sample in the chamber. A plurality of heating lamps may be mounted to the chamber and positioned to heat the sample. The sample may be placed in the first and the second cooled fixtures. The sample may be heated to a specific temperature using the heating lamps. Radiation may be directed though the window material, the radiation thereafter interacting with the sample and exiting the chamber through the window material.

High-temperature strain cell for tomographic imaging

Growing community of inventors

Berkeley, CA, United States of America

Robert O Ritchie