  Many devices, including touchscreens and robotic hands, involve frictional
contacts. Optimizing these devices requires fine control of the interface's
friction law. We lack systematic methods to create dry contact interfaces whose
frictional behavior satisfies preset specifications. We propose a generic
surface design strategy to prepare dry rough interfaces that have predefined
relationships between normal and friction forces. Such metainterfaces
circumvent the usual multiscale challenge of tribology by considering
simplified surface topographies as assemblies of spherical asperities.
Optimizing the individual asperities' heights enables specific friction laws to
be targeted. Through various centimeter-scaled elastomer-glass metainterfaces,
we illustrate three types of achievable friction laws, including linear laws
with a specified friction coefficient and unusual nonlinear laws. This design
strategy represents a scale- and material-independent, chemical-free pathway
toward energy-saving and adaptable smart interfaces.
