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The field of bioelectronics with the aim to contact cells, cell clusters, biological tissues and organoids has become a vast enterprise. Currently, it is mainly relying on classical micro‐ and nanofabrication methods to build devices and systems. Very recently the field is highly pushed by the development of novel printable organic, inorganic and biomaterials as well as advanced digital printing technologies such as laser and inkjet printing employed in this endeavor. Recent advantages in alternative additive manufacturing and 3D printing methods enable interesting new routes, in particular for applications requiring the incorporation of delicate biomaterials or creation of 3D scaffold structures that show a high potential for bioelectronics and building of hybrid bio‐/inorganic devices. Here the current state of printed 2D and 3D electronic structures and related lithography techniques for the interfacing of electronic devices with biological systems are reviewed. The focus lies on in vitro applications for interfacing single cell, cell clusters, and organoids. Challenges and future prospects are discussed for all‐printed hybrid bio/electronic systems targeting biomedical research, diagnostics, and health monitoring. [ABSTRACT FROM AUTHOR]

Printed electronics including large‐area sensing, wearables, and bioelectronic systems are often limited to simple circuits and hence it remains a major challenge to efficiently store data and perform computational tasks. Memristors can be considered as ideal candidates for both purposes. Herein, an inkjet‐printed memristor is demonstrated, which can serve as a digital information storage device, or as an artificial synapse for neuromorphic circuits. This is achieved by suitable manipulation of the ion species in the active layer of the device. For digital‐type memristor operation resistive switching is dominated by cation movement after an initial electroforming step. It allows the device to be utilized as non‐volatile digital memristor, which offers high endurance over 12 672 switching cycles and high uniformity at low operating voltages. To use the device as an electroforming‐free, interface‐based, analog‐type memristor, anion migration is exploited which leads to volatile resistive switching. An important figure of merits such as short‐term plasticity with close to biological synapse timescales is demonstrated, for facilitation (10–177 ms), augmentation (10s), and potentiation (35 s). Furthermore, the device is thoroughly studied regarding its metaplasticity for memory formation. Last but not least, the inkjet‐printed artificial synapse shows non‐linear signal integration and low‐frequency filtering capabilities, which renders it a good candidate for neuromorphic computing architectures, such as reservoir computing. [ABSTRACT FROM AUTHOR]

Printed and flexible metal-oxide transistor technology has recently demonstrated great promise due to its high performance and robust mechanical stability. Herein, fully printed inverter structures using electrolyte-gated oxide transistors on a flexible polyimide (PI) substrate are discussed in detail. Conductive graphene ink is printed as the passive structures and interconnects. The additive printed transistors on PI substrates show an Ion=Ioff ratio of 106 and show mobilities similar to the state-of-the-art printed transistors on rigid substrates. Printed meander structures of graphene are used as pull-up resistances in a transistor-- resistor logic to create fully printed inverters. The printed and flexible inverters show a signal gain of 3.5 and a propagation delay of 30 ms. These printed inverters are able to withstand a tensile strain of 1.5% following more than 200 cycles of mechanical bending. The stability of the electrical direct current (DC) properties has been observed over a period of 5 weeks. These oxide transistor-based fully printed inverters are relevant for digital printing methods which could be implemented into roll-to-roll processes. [ABSTRACT FROM AUTHOR]

Keywords: electrolyte-gated transistors; ink-jet print; ion-gels; ionic liquids; printed electronics The self-assembling ion-gel can be ink-jet printed and therefore enables printing of chemically crosslinked ion-gels. Electrolyte-gated transistors, ink-jet print, ion-gels, ionic liquids, printed electronics. [Extracted from the article]

Electrolyte‐gated transistors (EGTs) represent an interesting alternative to conventional dielectric‐gating to reduce the required high supply voltage for printed electronic applications. Here, a type of ink‐jet printable ion‐gel is introduced and optimized to fabricate a chemically crosslinked ion‐gel by self‐assembled gelation, without additional crosslinking processes, e.g., UV‐curing. For the self‐assembled gelation, poly(vinyl alcohol) and poly(ethylene‐alt‐maleic anhydride) are used as the polymer backbone and chemical crosslinker, respectively, and 1‐ethyl‐3‐methylimidazolium trifluoromethanesulfonate ([EMIM][OTf]) is utilized as an ionic species to ensure ionic conductivity. The as‐synthesized ion‐gel exhibits an ionic conductivity of ≈5 mS cm−1 and an effective capacitance of 5.4 µF cm−2 at 1 Hz. The ion‐gel is successfully employed in EGTs with an indium oxide (In2O3) channel, which shows on/off‐ratios of up to 1.3 × 106 and a subthreshold swing of 80.62 mV dec−1. [ABSTRACT FROM AUTHOR]