  The miniaturization of machines towards the micron and nanoscales requires
the development of joint-like elements that enable and constrain motion. We
present a facile method to create colloidal joints, that is, anisotropic
colloidal particles containing surface mobile DNA linkers that control the
motion range of bonded particles. We demonstrate quantitatively that we can
control the flexibility of these colloidal joints by tuning the DNA linker
concentration in the bond area. We show that the colloidal shape controls the
range of motion that these colloidal joints enable, due to the finite-sized
patch of bonded linkers that cannot cross regions of high curvature. Finally we
demonstrate the potential of the colloidal joints for programmable bottom-up
self-assembly by creating flexible colloidal molecules and colloidal polymers.
The reconfigurability and motion constraint offered by our colloidal joints
make them promising building blocks for the development of switchable materials
and nanorobots.
