INTERACTIONS.ACM.ORG JANUARY–FEBRUARY 2020 INTERACTIONS 89
near future, as interest from the HCI
community is growing [ 4], but so far
there is still much to explore.
ARE THE MACHINE
Traditionally, metamaterials were
understood as materials—we think of
them as devices.
We argue that viewing metamaterials
as devices allows us to push the boundaries
of metamaterials further. In our research,
we propose unifying material and device
to develop metamaterial devices. Such
metamaterial devices can receive
input and process the information
to produce output (Figure 3). To
instantiate these new types of devices,
we investigated three key elements
• Materials that process analog inputs
by implementing mechanisms based on
their microstructure [ 5]
• Materials that process digital signals
by embedding mechanical computation
into the object’s microstructure [ 6]
• Interactive metamaterial objects
that output information to the user by
changing their outside textures [ 7].
The design of such intricate
microstructures, which enable the
functionality of metamaterial devices,
is challenging. The complexity of
the design arises from the fact that
not only is a suitable cell geometry
necessary, but also that cells need to
play together in a well-defined way.
Figure 5 illustrates how cell constraints
interact, which makes their design
difficult. To support users in designing
such microstructures, we create tools
that optimize the cell structures and
autogenerate cell assemblies from high-level user input [ 8].
Because metamaterial devices are
defined by their geometry, they employ
• No assembly. The key benefit of our
approach is that the resulting devices
can be 3D-printed in one piece and
thus do not require assembly. This
means that they can be 3D-printed as
a part of a larger structure, such as a
full door, including latch mechanism
• Sustainability. Metamaterial devices
are printed from a single material. This
makes them easy to recycle, in contrast
to composite materials. Moreover,
metamaterials tend to save material due
to their inherently porous structure.
• Printability. Although
metamaterials are complex structures,
they can be designed to be easy to print.
The structure can be optimized
Figure 1. (a) Metamaterials typically consist of flexures, or buckling or bistable beams as basic building blocks of their cells. (b) Connecting
multiple unit cells enables unusual properties, such as volume-changing materials. (c) In addition to 3D cells, origami- and kirigami-based
metamaterials exert interesting properties.
flexures buckling bistable kirigami origami conventional material volume-changing material (auxetic)