Attendees at this year’s International Electron Devices Meeting (IEDM) were delighted and perhaps somewhat horrified when the plenary speaker popped some electronics gear in his mouth and proclaimed, “It tastes like chicken!” The speaker, John Rogers from the University of Illinois at Champaign-Urbana, was demonstrating the edible nature of what he called transient electronics, which are designed from elements that rapidly decompose and are harmless to the human body and to the environment. One possible application of such bio-integrated electronics: They could be placed below a suture and provide enough heat through a resistive element to kill bacteria over a two week period. Bacteria sewn into the body during an operation are often the cause of a return trip to the hospital and delayed recovery.
He demonstrated that a very thin layer of silicon will dissolve in water fairly rapidly, in a matter of hours, turning into a salicylic acid. Circuits were completed with silicon dioxide as a gate dielectric and insulator and Manganese as the interconnect and resistor material. Levels were well below the FDA’s recommended daily allowance. Silk, already approved by the FDA for such applications, was used as the substrate. “You don’t want to chew,” Rogers quipped during his demonstration.
He said other applications of transient electronics include the use of sensors in chemical spills, which would monitor the presence of the chemical over time and then dissolve away, and even in consumer electronics, where lifetime would be measured in years instead of weeks.
Rogers also described another class of bioelectronics he called silicon membranes. By making silicon-based electronics thin enough, they can be stretchable. With a serpentine design, an applied strain of 30% induces strains that are less than 0.65%. These devices can conformally laminate onto the surface of the skin, in a manner that is mechanically invisible to the user, much like a temporary transfer tattoo. The systems, referred to as epidermal electronics, attach intimately and physically couple to rough skin surfaces, via van der Waals forces alone, with the ability accommodate natural and induced motions, Rogers noted in the accompanying paper.
Other bioelectronic applications include brain surgery, interfaces for human/computer control systems, skin-based physiological status monitors, high resolution electrical mapping systems for electrocorticography, and “instrumented” multifunctional balloon catheters for cardiac ablation therapy.