This week has seen the publishing of a fairly major breakthrough in the field of man/machine interfacing. The epidermal electronic system (EES) developed by researchers from the University of Illinois Urbana-Champaign (and numerous other institutions) have developed a technique which allows the transfer of circuitry onto human skin using techniques identical to that of a temporary tattoo. This gives me the rare excuse to write some proper science.
The task of integrating circuitry with the human body is a major challenge for bioengineers. Implanted electronics are expensive to manufacture and require invasive implantation and expensive solutions to problems such as power and biodegradation. However the potential pay-offs medically are huge. The prospect of of real-time physiological, electro-physiological and biomechanical monitoring facilitated in a few minutes is extremely attractive to the healthcare industry.
EES actually uses fairly conventional technology. Circuit components are manufactured using photolithography and held by a rubbery elastomer attached with water soluble glue to a paper backing. The transfer is placed against the skin and wetted at which point the paper comes away freely. This circuit adheres to the skin by the bulk force of Van der Waals attraction (hydrogen bonding). You will note that this is exactly analogous to the type of temporary tattoo you used to get a children’s parties.
However innovation has been required in a couple of areas. The technology would not be possible without the miniaturisation of active components (transistors, capacitors etc.) to below the size of the skin’s microscopic topographical features. This was achieved using ultrathin layouts (<7 μm) and established electronic materials in the form of filamentary serpentine nanoribbons and micro- and nanomembranes. I am not entirely sure what filamentary serpentine nanoribbons are but they sound jolly clever.
Optimised geometrical configuration in of the circuit interconnections limits the the deformation of the circuit when the skin underneath stretches or is pinched. Importantly by matching macromechanical properties such as Young’s modulus the elastic response of the of the film can be reconciled with that of the skin. This greatly reduced the tendency of the device to simple fall off meaning it can be used for over 24hrs. The researchers even claim that the electrical contact with the skin is good enough to use the circuits for ECG and EEG.
In fact they have used the platorm to demonstrate:
[a] collection of multifunctional sensors (such as temperature, strain, and electrophysiological), microscale light-emitting diodes (LEDs), active/passive circuit elements (such as transistors, diodes, and resistors), wireless power coils, and devices for radio frequency (RF) communications (such as high-frequency inductors, capacitors, oscillators, and antennae)
The potential applications of circuits built using these components are almost endless. I have no doubt the there will be strong commercial and military interest in this technology . It is easy to imagine circuits being integrated with illustrative designs and used in sport, shopping, clubbing and fashion especially if the longevity is increased. We could see the narrowing of the boundary between man and machine beyond that of a cyberpunk’s wettest dreams.
- Dae-Hyeong Kim et al (2011), Epidermal Electronics, Science Vol. 333 no. 6044 pp. 838-843,