2022-010 – Optical Programmed Colloidal Geodes: Enabling Advanced Coating Technology

A longstanding problem in the design of optical materials is engineering the response over multiple spectral bands. Solving this problem is essential to manufacturing functional materials for energy harvesting, thermal management, and coatings. Materials for radiative cooling, for example, must strongly scatter visible wavelengths while strongly absorbing (and re-radiating) mid-infrared (IR) radiation, while ultraviolet (UV)-protective coatings must absorb or reflect UV light while reflecting near IR strongly. To engineer a response in multiple bands, one must combine components that have optical resonances in different spectral regions. Because the choice of components and the way they are combined generally depend on the application, it is slow to fabricate and deploy such materials. Semiconductor nanowires with nanoscale-engineered morphologies offer unparalleled control over the frequencies and widths of resonances from the UV to IR, but they are difficult to incorporate into flow processes, owing to their lack of colloidal stability and inability to be produced at scale. Conversely, colloidal microspheres are readily incorporated into flow processes and easily stabilized, but their dielectric and plasmonic resonances tend to be broad due to their spherical geometry. Thus, there is a need for easily fabricated and versatile materials that provide a programmable optical response across multiple bands simultaneously.

Technology Description:
Researchers at the University of New Mexico, Harvard University and the Georgia Institute of Technology have collaborated to propose hierarchically structured materials based on colloidal nanowire geodes. Nanowire geodes are hollow colloidal particles with semiconductor nanowires decorating their interior, and whose composition and structure are “programmed” with nanoscale precision to yield a desired optical response. Geodes combine the many optical properties of nanowires with the processability of conventional colloidal particles, and constitute a versatile photonic materials platform for a range of applications. Their hierarchical structure can be controlled at each length scale, which is critical to achieving the goal of programmability over multiple spectral bands. Based on the above characteristics, micro-geode paints offer a combination of cooling power, ease of deployment, manufacturing scalability, aesthetics, and operational durability that does not exist today.






  • Stronger control over the frequencies and widths of resonances
  • Readily incorporates into flow processes and easily stabilized
  • Programmability over multiple spectral bands
  • Offers both color and thermal performance, reducing paint formulation complexity
  • Proposed process enables bulk production

Potential Applications:

  • Broad-spectrum camouflage
  • Exterior coatings for space vehicles for heat management
  • Radiatively cooled rooftop coatings
  • Cooling paint/coating

Contact Information:

Name: Andrew Roerick

Email: aroerick@innovations.unm.edu

Phone: 505-277-0608