Kavli Affiliate: Itai Cohen
| First 5 Authors: Prateek Sehgal, Meera Ramaswamy, Edward Y. X. Ong, Christopher Ness, Itai Cohen
| Summary:
Metamaterials are composite structures whose properties arise from a
mesoscale organization of their constituents. Provided this organization occurs
on scales smaller than the characteristic lengths associated with their
response, it is often possible to design such materials to have properties that
are otherwise impossible to achieve with conventional materials — including
negative indexes of refraction, perfect absorption of electromagnetic
radiation, and negative Poisson ratios. Here, we introduce and demonstrate a
new material class: viscosity metamaterials. Specifically, we show that we are
able to rapidly drive large viscosity oscillations in a shear-thickened fluid
using acoustic perturbations with kHz to MHz frequencies. Because the time
scale for these oscillations can be orders of magnitude smaller than the
timescales associated with the global material flow, we can construct
metamaterials whose resulting viscosity is a composite of the thickened,
high-viscosity and dethickened, low viscosity states. Such viscosity
metamaterials can be used to engineer a variety of surprising properties
including negative viscosities, a response that is inconceivable with
conventional fluids. The high degree of control over the resulting viscosity,
the ease with which they can be accessed, and the variety of exotic properties
achievable by viscosity metamaterials make them attractive for uses in
technologies for which control over fluid flows and their instabilities are
critical, ranging from coatings to cloaking to 3D printing.
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