A resurgence in organic technology is set to transform the world of electronic devices, offering a way to give the very fabric of life enhanced functionality.
The transition from basic science to practical technology is rarely linear. The common view that promising discoveries need only patience, hard work and money to attain commercial success is seldom correct. Often, all kinds of technical, economic and social drivers must also coincide. So forecasts of fortune may fail and fade, only for the idea to re-emerge when the climate is more favourable.
Such a resurgence is now under way in organic electronics, in which polymers and other organic molecules are the active materials in information processing. Hideki Shirakawa discovered in the late 1960s that insulating plastics in the form of polyacetylene films could be made to conduct electricity. Chemists Alan Heeger and Alan MacDiarmid collaborated with Shirakawa in 1976to boost the material’s conductivity by doping with halogens, and went on to make a ‘polymer battery’.
Greeted enthusiastically by some firms, this early work soon stalled — the polymers were too unstable and difficult to process, and their properties were hard to control and reproduce reliably. The situation changed in the late 1980s, when Richard Friend and co-workers at the University of Cambridge, UK, found that poly(p-phenylene vinylene)could conduct without doping and could be stimulated to emit light, paving the way for polymer light-emitting diodes. It began to seem possible that such substances could be used to make lightweight, flexible devices through simple printing and coating techniques.
The synthesis of gossamer-thin organic electronic circuits by Martin Kaltenbrunner at the University of Tokyo and his colleagues (see page 458) is the latest example of the ingenuity driving this field. Their devices elegantly blend new and old materials and techniques. The substrate is a 1-micrometre-thick plastic foil; organic small molecules provide the semiconductor for the transistors; other organic molecules and alumina make up the insulating layers; and the electrodes are ultrathin aluminium. The plastic films — 27 times lighter than office paper — can be crumpled like paper and stretched to more than double their length without impairing the device’s performance. Adding a pressure-sensitive rubber layer produces a touch-sensing foil that could serve as electronic skin or in medical prostheses.
Wearable and flexible devices have recently made great strides, propelled in particular by the work of John Rogers’ group at the University of Illinois at Urbana-Champaign. Made from materials that biodegrade safely, such devices can now be printed on or attached directly to human skin. The possibilities for in situ monitoring of wound care, tissue repair, brain and heart function, and drug delivery are phenomenal; the challenge is for medical procedures to keep pace with the technology. Such applications show that organic electronics complements silicon logic, taking information processing into areas that silicon will never reach.
These technologies seem potentially transformative — more so on current showing than graphene. The latest work continues the trend towards a smart environment in which all kinds of functionality are invisibly embedded. What happens when clothing, money and even flesh and blood can receive, process and send information; when the fabric of daily life can be turned, unseen, into a computing and sensing device? Most narratives currently dwell on fears of surveillance or benefits of round-the-clock medical checks and diagnoses. But past experience should teach us that technologies don’t simply get superimposed on the quotidian — they both shape and are shaped by human behaviour. Whether or not we get what is good for us, it probably won’t be what we expect.
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Plastic fantastic. Nature 499, 379 (2013). https://doi.org/10.1038/499379a