A thermoelectric device includes a thermally conductive first plate and at least one thermoelectric sub-assembly comprises a thermally conductive second plate and a plurality of thermoelectric elements in a region between the first plate and the second plate. The at least one thermoelectric sub-assembly further includes a first material along a first portion of a perimeter of the region and having a first stiffness and a second material along a second portion of the perimeter of the region and having a second stiffness less than the first stiffness.