Figure 1.

Example of TP vs. AP processes. (Top) TP process steps, starting with Si donor substrate. Includes procedures such as depositing a sacrificial layer, using solvent for stripping sacrificial layer, and transfer printing by an intermediate elastomeric substrate; (Bottom) AP process obviates the need for sacrificial layer, use of solvents, or use of an intermediate elastomer for transfer printing. Instead, a weakly-adhering donor is used, from which reversed metallization and a combined polymer deposition and photolithography step are implemented to create an inverted sensor. Because the sensor is inverted on a weakly-adhering surface, peel-off is performed directly by adhesive. Both processes result in a similar sensor embedded within adhesive; the latter requires fewer steps and materials.