  Gears and cogwheels restrain degrees of freedom and channel power into a
specified motion. They are fundamental components of macroscopic machines.
Interlocking microrotors similarly constitute key elements toward feasible
micromachinery. Their assembly, positioning and control is a challenge at
microscale, where noise is ubiquituous. Here, we show the assembly and control
of a family of self-spinning cogwheels with varying teeth numbers and study
interlocking mechanisms in systems of multiple cogwheels. The cogwheels are
autonomous and active, with teeth formed by colloidal microswimmers that power
the structure, and control its rotation rate. Leveraging the angular momentum
of light with optical vortices, we control the direction of rotation of the
cogwheels. We study pairs of interlocking cogwheels, that roll over each other
in a random walk and curvature-dependent mobility. We leverage this feature to
achieve self-positioning of cogwheels on structures with variable curvature and
program microbots, notably demonstrating the ability to pick up, displace and
release a load. This work highlights untapped opportunities of manufacturing at
microscale using self-positioning components and constitutes an important step
towards autonomous and programmable microbots.
