<p>Metamaterials
are artificially structured materials which attain their unconventional macroscopic
properties from their cellular configuration rather than their constituent
chemical composition. The judicious design of this cellular structure opens the
possibility to program and control the optical, mechanical, acoustic,
or thermal responses of metamaterials. This Ph.D. dissertation focuses on
scalable design and manufacturing strategies for optical and
mechanical metamaterials.<br>
<br>
</p>
<p>The
fabrication of optical metamaterials still relies heavily on low-throughput
process such as electron beam lithography,
which is a serial technique. Thus, there is a growing need for
the development of high-throughput, parallel processes to make the fabrication
of optical
metamaterials more accessible and cost-effective. The first part of this
dissertation presents a scalable manufacturing method, termed “roll-to-roll
laser induced superplasticity” (R2RLIS), for the production of
flexible optical metamaterials, specifically metallic near-perfect absorbers. R2RLIS
enables the rapid and inexpensive fabrication of ultra-smooth metallic
nanostructures over large areas using conventional CO<sub>2</sub> engravers
or inexpensive diode lasers. Using low-cost metal/epoxy nanomolds,
the minimum feature size obtained by R2RLIS was <40 nm,
facilitating the rapid fabrication of flexible near-perfect absorbers at
visible
frequencies with the capability to wrap around non-planar surfaces.</p>
<p> </p>
<p>The
existing approaches for designing mechanical metamaterials are mostly <i>ad hoc</i>,
and rely heavily on intuition and
trial-and-error. A rational and systematic approach to create functional and
programmable mechanical metamaterials is therefore desirable to unlock
the
vast design space of mechanical properties. The second part of this
dissertation introduces a systematic, algorithmic design strategy based on Voronoi
tessellation to create architected soft machines (ASMs)
and twisting mechanical metamaterials (TMMs) with programmable motion and properties.
ASMs are a new class of soft machines that benefit from their
3D-architected structure to expand the range of mechanical properties and
behaviors achievable
by 3D printed soft robots. On tendon-based actuation, ASMs deform according
to
the topologically encoded buckling of their structure to produce a wide range
of motions such
as contraction, twisting, bending, and cyclic motion. TMMs are a new class of
chiral mechanical metamaterials which exhibit compression-twist coupling, a
property absent in isotropic materials. This property manifests
macroscopically and is independent of the flexible
material chosen to fabricate the TMM. The nature of this compression-twist
coupling can be programmed by simply tuning two design parameters, giving
access to distinct twisting regimes and tunable onset
of auxetic (negative Poisson’s ratio) behavior. Taking a
metamaterial approach toward the design of soft machines substantially
increases their number of degrees of freedom in deformation, thus blurring
the boundary between materials and machines.</p>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/12532760 |
| Date | 23 June 2020 |
| Creators | Debkalpa Goswami (9006635) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/thesis/Design_and_Manufacturing_of_Flexible_Optical_and_Mechanical_Metamaterials/12532760 |
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