  We examine square and kagome artificial spin ice for colloids confined in
arrays of double-well traps. Unlike magnetic artificial spin ices, colloidal
and vortex artificial spin ice realizations allow creation of doping sites
through double occupation of individual traps. We find that doping square and
kagome ice geometries produces opposite effects. For square ice, doping creates
local excitations in the ground state configuration that produce a local
melting effect as the temperature is raised. In contrast, the kagome ice ground
state can absorb the doping charge without generating non-ground-state
excitations, while at elevated temperatures the hopping of individual colloids
is suppressed near the doping sites. These results indicate that in the square
ice, doping adds degeneracy to the ordered ground state and creates local weak
spots, while in the kagome ice, which has a highly degenerate ground state,
doping locally decreases the degeneracy and creates local hard regions.
