A body-mountable device may include a first layer, a second layer, and an electronic structure. The first layer may include a first topographical feature, while the second layer may include a second topographical feature. The first topographical feature and the second topographical feature may be reciprocally-shaped. The second layer may be mounted on the first layer such that the first topographical feature interfaces with the second topographical feature, thereby mechanically securing the second layer to the first layer. The electronic structure, which may include an antenna, a sensor, and an electronic device, may be embedded in the second layer. In an example in which the body-mountable device is an eye-mountable device, the first layer may be a posterior lens, and the second layer may be an anterior lens.
