  In this paper we present FootTile, a foot sensor for reaction force and
center of pressure sensing in challenging terrain. We compare our sensor design
to standard biomechanical devices, force plates and pressure plates. We show
that FootTile can accurately estimate force and pressure distribution during
legged locomotion. FootTile weighs 0.9g, has a sampling rate of 330Hz, a
footprint of 10 by 10mm and can easily be adapted in sensor range to the
required load case. In three experiments we validate: first the performance of
the individual sensor, second an array of FootTiles for center of pressure
sensing and third the ground reaction force estimation during locomotion in
granular substrate. We then go on to show the accurate sensing capabilities of
the waterproof sensor in liquid mud, as a showcase for real world rough terrain
use.
