Fig. 15. (A) Schematic of ultrathin devices on a carrier wafer, transfer printing onto a freestanding silk film followed by dissolution and the procedure of the animal toxicity test: image before (left) and shortly after (center) and two weeks after (right) implantation. Reprinted with permission from ref. 21 Copyright © 2009 AIP Publishing. (B) The Mg heater was encapsulated in a silk “pocket” that protects the electronics and can be used to program the lifetime of the device. In vitro: (C) the devices were placed underneath bacterial cultures of S. aureus grown on agar plates and powered to achieve a desired temperature, monitored using an IR camera. A clear zone of inhibition, after heat treatment and overnight incubation, appeared in correspondence to the area of heat treatment application. (D) Monitoring of device degradation and tracing of Mg ions. Devices were implanted and examined after 7 and 15 days. Reprinted with permission from ref. 119 Copyright © 2014 National Academy of Sciences USA.