New Mighty Microlattice Material Weighs Next to Nothing
Nov 18, 2011 11:53 AM PT
A team of researchers led by Tobias Schaedler of HRL Labs has developed an ultralight metallic microlattice that's 10,000 times lighter than ultralight aerogels and carbon nanotube foams.
Ultralight cellular materials weigh less than 10 milligrams per cubic centimeter.
"An ordered lattice is inherently stronger than a foam with random porosity," Schaedler told TechNewsWorld.
Uses for ultralight cellular materials include thermal insulation, battery electrodes and damping for acoustic, vibration and shock energy.
This latest research, published in the journal Science, is part of a cycle that began back in 2007.
How the Ultralight Metallic Microlattice Was Made
The research team first made a polymer microlattice template by exploiting an optical trick for growing polymer fibers using light, Schaedler said.
The process passes ultraviolet (UV) light through a perforated mask into a reservoir of resin that gets cured when it's exposed to UV.
The resin traps light as it cures under each hole in the mask and forms a polymer fiber along the path of the light.
Playing multiple light beams over the mask makes the fibers interconnect to form a lattice.
The remaining uncured resin is washed out, the polymer template is coated in a thin layer of nickel, and the polymer is dissolved with lye, also known as sodium hydroxide.
This leaves a "very thin" hollow lattice surrounding the original template, Schaedler said.
Using a 3D Truss
A three-dimensional truss-like pattern similar to that used in bridge supports lies at the core of this ultralight microlattice research.
"We developed this microtruss process at HRL in 2007, and we've been working on multiple applications since," Schaedler said.
The Microlattice vs. Aerogels
HRL Labs' ultralight metallic microlattice has a density of less than 0.9 mg per cubic centimeter -- less than one-thousandth of the density of water. It recovers completely after compression exceeding 50 percent strain and has an energy absorption similar to elastomers.
The metallic microlattice rates as E p2 on Young's modulus E, whereas ultralight aerogels and carbon nanotube foams with stochastic architecture rate at E p3, the researchers said.
Young's modulus basically describes tensile elasticity -- the tendency of an object to deform along an axis when compressed.
The difference between Young's modulus ratings of p2 and p3 isn't linear.
"It scales with relative density, so if you have a relative density of 1 percent, the difference is a factor of 100, and if you have a relative density of 0.01 percent like the lightest lattice we were able to make, the difference would be a factor of 10,000," Schaedler said.
The Long Road of Research
HRL had earlier conducted research with the California Institute of Technology and the University of California at Irvine "for making [this microtruss process] ultralight," Schaedler said.
The findings of that earlier project were published in Nanoletters in August.