An ultra-lightweight design for imperceptible plastic electronics.

Electronic devices have advanced from their heavy, bulky origins to become smart, mobile appliances. Nevertheless, they remain rigid, which precludes their intimate integration into everyday life. Flexible, textile and stretchable electronics are emerging research areas and may yield mainstream technologies. Rollable and unbreakable backplanes with amorphous silicon field-effect transistors on steel substrates only 3 µm thick have been demonstrated. On polymer substrates, bending radii of 0.1 mm have been achieved in flexible electronic devices. Concurrently, the need for compliant electronics that can not only be flexed but also conform to three-dimensional shapes has emerged. Approaches include the transfer of ultrathin polyimide layers encapsulating silicon CMOS circuits onto pre-stretched elastomers, the use of conductive elastomers integrated with organic field-effect transistors (OFETs) on polyimide islands, and fabrication of OFETs and gold interconnects on elastic substrates to realize pressure, temperature and optical sensors. Here we present a platform that makes electronics both virtually unbreakable and imperceptible. Fabricated directly on ultrathin (1 µm) polymer foils, our electronic circuits are light (3 g m(-2)) and ultraflexible and conform to their ambient, dynamic environment. Organic transistors with an ultra-dense oxide gate dielectric a few nanometres thick formed at room temperature enable sophisticated large-area electronic foils with unprecedented mechanical and environmental stability: they withstand repeated bending to radii of 5 µm and less, can be crumpled like paper, accommodate stretching up to 230% on prestrained elastomers, and can be operated at high temperatures and in aqueous environments. Because manufacturing costs of organic electronics are potentially low, imperceptible electronic foils may be as common in the future as plastic wrap is today. Applications include matrix-addressed tactile sensor foils for health care and monitoring, thin-film heaters, temperature and infrared sensors, displays, and organic solar cells.

A few-layer molecular film on polymer substrates to enhance the performance of organic devices.

In organic electronics the functionalization of dielectric substrates with self-assembled monolayers is regarded as an effective surface modification strategy that may significantly improve the resulting device performance. However, this technique is not suitable for polymer substrates typically used in flexible electronics. Here, we report organic modifiers based on a paraffinic tripodal triptycene, which self-assembles into a completely oriented two-dimensional hexagonal triptycene array and one-dimensional layer stacking structure on polymer surfaces. Such few-layer films are analogous to conventional self-assembled monolayers on inorganic substrates in that they neutralize the polymer surface. Furthermore, the triptycene films significantly improve the crystallinity of an organic semiconductor and the overall performance of organic thin-film transistors, therefore enabling the fabrication of high-performance organic complementary circuits on polymer substrates with high oscillation speeds and low operation voltage.

Flexible low-voltage organic transistors with high thermal stability at 250 °C.

Low-operating-voltage flexible organic thin-film transistors with high thermal stability using DPh-DNTT and SAM gate dielectrics are reported. The mobility of the transistors are decreased by 23% after heating to 250 °C for 30 min. Furthermore, flexible organic pseudo-CMOS inverter circuits, which are functional after heating to 200 °C, are demonstrated.