Innovation and Partnerships Office

Luminescent Nanocrystal Stress Gauge JIB-2727


  • Biomechanics
  • Cancer research
  • Polymer chemistry
  • Optomechanical devices
  • Failure analysis


  • Nanonewton sensitivity
  • Nanoscale spatial resolution
  • Fluorescent signal


A team of Berkeley Lab scientists led by Paul Alivisatos and Charina Choi has developed a nanoscale stress sensor made of spider-like, tetrapod particles that change their optoelectronic properties when subject to forces. Tests of these structures squeezed within the tiny confines of diamond anvil cells and stretched within single polymer fibers have demonstrated a shift in their fluorescence wavelength in response to nanonewton-order forces.

The tetrapod nanostructures consist of a 4 nm cadmium selenide core connecting four flexible cadmium sulfide legs (~15-40 nm). The core itself is a spherical “quantum dot,” an extraordinarily small semiconductor that is luminescent upon optical excitation. The legs of these structures will bend elastically with the application of force. When they bend, the fluorescent light emitted from the quantum dot core shifts to a lower wavelength in proportion to the strength of the force. The measurement of this red-shift translates into a measurement of force on the order of nanonewtons. The tetrapod nanostructure can be built from other materials, including zinc-containing semiconductors that are non-toxic to biological materials.

Mechanical force plays a role in many biological processes, including cancer metastasis, cell motility, and stem cell differentiation. However, cellular mechanics are ultimately generated by structures at the scale of a single protein, and current techniques cannot map forces with nanoscale spatial resolution. Furthermore, current techniques do not allow for in vivo measurements.

The Berkeley Lab nanoscale tetrapods can be placed in laboratory dishes to study the force exerted within individual cells or among cells acting in concert, such as those of beating heart tissue. Cancer research may benefit from precise measurement of cellular force interactions in light of research indicating that metastatic cells exert more force on their surrounding environment. Materials scientists will be able to use nanoscale stress sensors to develop a deeper understanding of why some materials remain strong while others fail. Thus, the Berkeley Lab sensor will have multiple applications in many laboratories.

DEVELOPMENT STAGE:  Proven principle.

STATUS:  Patent pending.  Available for licensing or collaborative research.


Choi, C.L., Li, H., Olson, A.C.K., Jain, P.K., Sivasankar, S., Alivisatos, A.P., “Spatially Indirect Emission in a Luminescent Nanocrystal Molecule,” Nano Letters, Vol. 11, No. 6, pp.2358-2362, 2011.

Choi, C.L., Koski, K.J., Olson, A.C.K., Alivisatos, A.P., “Luminescent nanocrystal stress gauge,” Proceedings of the National Academies of Science, Vol. 107, No. 50, pp. 21306-21310, 2010.

Choi, C.L., Koski, K.J., Sivasankar, S., Alivisatos, P.A., “Strain-Dependent Photoluminescence Behavior of CdSe/CdS Nanocrystals with Spherical, Linear, and Branched Topologies,” Nano Letters. Vol. 9, No. 10, pp. 3455-3549, 2009.


Modifying Nanocrystal Surfaces for Molecular Imaging and Electrical Devices, IB-2616

Rapid Detection of Cell Motility Using Semiconductor Nanocrystals, IB-1755