The organic electrochemical transistor (OECT), capable of transducing small ionic fluxes into electronic signals in an aqueous environment, is an ideal device to utilize in bioelectronic applications. Currently, most OECTs are fabricated with commercially available conducting poly(3,4-ethylenedioxythiophene) (PEDOT)-based suspensions and are therefore operated in depletion mode. Here, we present a series of semiconducting polymers designed to elucidate important structure–property guidelines required for accumulation mode OECT operation. We discuss key aspects relating to OECT performance such as ion and hole transport, electrochromic properties, operational voltage, and stability. The demonstration of our molecular design strategy is the fabrication of accumulation mode OECTs that clearly outperform state-of-the-art PEDOT-based devices, and show stability under aqueous operation without the need for formulation additives and cross-linkers.

Organic electrochemical transistors (OECTs) are receiving significant attention due to their ability to efficiently transduce biological signals. A major limitation of this technology is that only p-type materials have been reported, which precludes the development of complementary circuits, and limits sensor technologies. Here, we report the first ever n-type OECT, with relatively balanced ambipolar charge transport characteristics based on a polymer that supports both hole and electron transport along its backbone when doped through an aqueous electrolyte and in the presence of oxygen. This new semiconducting polymer is designed specifically to facilitate ion transport and promote electrochemical doping. Stability measurements in water show no degradation when tested for 2 h under continuous cycling. This demonstration opens the possibility to develop complementary circuits based on OECTs and to improve the sophistication of bioelectronic devices.

Liquid electrolyte-gated organic field effect transistors and organic electrochemical transistors have recently emerged as powerful technology platforms for sensing and simulation of living cells and organisms. For such applications, the transistors are operated at a gate voltage around or below 0.3 V because prolonged application of a higher voltage bias can lead to membrane rupturing and cell death. This constraint often prevents the operation of the transistors at their maximum transconductance or most sensitive regime. Here, we exploit a solid-liquid dual-gate organic transistor structure, where the threshold voltage of the liquid-gated conduction channel is controlled by an additional gate that is separated from the channel by a metal-oxide gate dielectric. With this design, the threshold voltage of the "sensing channel" can be linearly tuned in a voltage window exceeding 0.4 V. We have demonstrated that the dual-gate structure enables a much better sensor response to the detachment of human mesenchymal stem cells. In general, the capability of tuning the optimal sensing bias will not only improve the device performance but also broaden the material selection for cell-based organic bioelectronics.

Typographical errors were inadvertently introduced into the unit of charge mobility during the production process, such that the correct unit cm 2 V À 1 s À 1 was incorrectly give as cm À 2 V À 1 s À 1 . These errors do not affect the analysis of the results presented in the Article.The penultimate sentence of the second paragraph of the Article should read 'Recently, the electron mobility of n-type polymers has increased rapidly, reaching values of more than 1.0 cm 2 V À 1 s À 1 in OFETs, 12-17 thus enabling n-type OECTs operating in accumulation mode.' Similarly, the final sentence of the fourth paragraph of the section 'Transistor characterization' should read 'The electron mobilities (m e ) were measured to be 1.0 Â 10 À 4 cm 2 V À 1 s À 1 for p(gNDI-T2) and 1.0 Â 10 À 5 cm 2 V À 1 s À 1 for p(gNDI-gT2).'

Bicyclic dibrominated C15 medium-ring ether hexahydrolaureoxanyne was produced directly from an acyclic model C15-epoxide when treated with NBS with water as the solvent.