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Electrically tunable metadevices can add novel functionalities to electronic and electromagnetic systems such as antennas and cloaking technologies. However, current microwave metadevices are based on materials that require sophisticated and expensive fabrication processes, and are not compatible with large-area and high-throughput deposition techniques on flexible platforms. Here we report reconfigurable microwave resonators that are electrically tuned by organic electrochemical transistors. The devices are fabricated via inkjet printing onto polyimide substrates using commercial metal nanoparticle and conducting polymer inks. By applying electrostatic gating to the polymer—a mixed ion–electron conductor—we show that the amplitude and frequency of different microwave resonant structures, including individual magnetic and electric split-ring resonators as well as a metasurface, can be modulated in the sub-5-GHz range. Electrically tunable metamaterial-inspired devices in the microwave range can be created by using resonators that are integrated with organic electrochemical transistors and are entirely fabricated via inkjet-printed onto polyimide substrates.

In the past two decades, organic electronic materials have enabled and accelerated a large and diverse set of technologies, from energy-harvesting devices and electromechanical actuators, to flexible and printed (opto)electronic circuitry. Among organic (semi)conductors, organic mixed ion-electronic conductors (OMIECs) are now at the center of renewed interest in organic electronics, as they are key drivers of recent developments in the fields of bioelectronics, energy storage, and neuromorphic computing. However, due to the relatively slow switching dynamics of organic electronics, their application in microwave technology, until recently, has been overlooked. Nonetheless, other unique properties of OMIECs, such as their substantial electrochemical tunability, charge-modulation range, and processability, make this field of use ripe with opportunities. In this work, the use of a series of solution-processed intrinsic OMIECs is demonstrated to actively tune the properties of metamaterial-inspired microwave devices, including an untethered bioelectrochemical sensing platform that requires no external power, and a tunable resonating structure with independent amplitude- and frequency-modulation. These devices showcase the considerable potential of OMIEC-based metadevices in autonomous bioelectronics and reconfigurable microwave optics.

The first demonstration of an n-type water-gated organic field-effect transistor (WGOFET) is here reported, along with simple water-gated complementary integrated circuits, in the form of inverting logic gates. For the n-type WGOFET active layer, high-electron-affinity organic semiconductors, including naphthalene diimide co-polymers and a soluble fullerene derivative, have been compared, with the latter enabling a high electric double layer capacitance in the range of 1 μF cm–2 in full accumulation and a mobility–capacitance product of 7 × 10–3 μF/V s. Short-term stability measurements indicate promising cycling robustness, despite operating the device in an environment typically considered harsh, especially for electron-transporting organic molecules. This work paves the way toward advanced circuitry design for signal conditioning and actuation in an aqueous environment and opens new perspectives in the implementation of active bio-organic interfaces for biosensing and neuromodulation.

Cell-based biosensors constitute a fundamental tool in biotechnology, and their relevance has greatly increased in recent years as a result of a surging demand for reduced animal testing and for high-throughput and cost-effective in vitro screening platforms dedicated to environmental and biomedical diagnostics, drug development, and toxicology. In this context, electrochemical/electronic cell-based biosensors represent a promising class of devices that enable long-term and real-time monitoring of cell physiology in a noninvasive and label-free fashion, with a remarkable potential for process automation and parallelization. Common limitations of this class of devices at large include the need for substrate surface modification strategies to ensure cell adhesion and immobilization, limited compatibility with complementary optical cell-probing techniques, and the need for frequency-dependent measurements, which rely on elaborated equivalent electrical circuit models for data analysis and interpretation. We hereby demonstrate the monitoring of cell adhesion and detachment through the time-dependent variations in the quasi-static characteristic current curves of a highly stable electrolyte-gated transistor, based on an optically transparent network of printable polymer-wrapped semiconducting carbon-nanotubes.

Inkjet printing is an attractive bottom-up microfabrication technology owing to its simplicity, ease of use, and low cost. This method is particularly suitable for patterning of biomaterials because biofunctionality and bioactivity can be preserved during the patterning process in the absence of harsh conditions such as heat, UV radiation, and plasma. However, it is still challenging to apply this technology to biomaterial-based soft photonics, which requires precise control over morphology and uniformity to confine photons efficiently. This study introduces inkjet printing to create silk protein patterns to emit/guide a single-mode distributed feedback (DFB) laser on a single platform. A thin TiO2 coated grating enables coherent feedback of the generated photons for any shape of the printed silk pattern. The lasing wavelength can be adjusted by adding gold nanoparticles to the silk/dye ink. Photonic components of lasers and waveguides are drawn on a DFB board, and the lasing light can be extracted through adjacent waveguides. The printed components can be reformed by post modification (water-removal and reprinting). Additionally, optically absorptive melanin nanoparticles placed on the waveguide can attenuate the propagating light, thus adding utility for sensing applications. This allows a new method to fabricate cost-effective, easily functionalized, and versatile biomaterial photonic chips for advanced sensing and diagnosis.

The use of natural or bioinspired materials to develop edible electronic devices is a potentially disruptive technology that can boost point-of-care testing. The technology exploits devices which can be safely ingested, along with pills or even food, and operated from within the gastrointestinal tract. Ingestible electronics could potentially target a significant number of biomedical applications, both as therapeutic and diagnostic tool, and this technology may also impact the food industry, by providing ingestible or food-compatible electronic tags that can smart track goods and monitor their quality along the distribution chain. We hereby propose temporary tattoo-paper as a simple and versatile platform for the integration of electronics onto food and pharmaceutical capsules. In particular, we demonstrate the fabrication of all-printed Organic Field-Effect Transistors (OFETs) on untreated commercial tattoo-paper, and their subsequent transfer and operation on edible substrates with a complex non-planar geometry.

Polymer semiconductors have been experiencing a remarkable improvement in electronic and optoelectronic properties, which are largely related to the recent development of a vast library of high-performance, donor-acceptor copolymers showing alternation of chemical moieties with different electronic affinities along their backbones. Such steady improvement is making conjugated polymers even more appealing for large-area and flexible electronic applications, from distributed and portable electronics to healthcare devices, where cost-effective manufacturing, light weight, and ease of integration represent key benefits. Recently, a strong boost to charge carrier mobility in polymer-based field-effect transistors, consistently achieving the range from 1.0 to 10 cm2 V-1 s-1 for both holes and electrons, has been given by uniaxial backbone alignment of polymers in thin films, inducing strong transport anisotropy and favoring enhanced transport properties along the alignment direction. Herein, an overview on this topic is provided with a focus on the processing-structure-property relationships that enable the controlled and uniform alignment of polymer films over large areas with scalable processes. The key aspects are specific molecular structures, such as planarized backbones with a reduced degree of conformational disorder, solution formulation with controlled aggregation, and deposition techniques inducing suitable directional flow.

We report power tunability in a fiber laser mode-locked with a solution-processed filtered graphene film on a fiber connector. ∼370 fs pulses are generated with output power continuously tunable from ∼4 up to ∼52 mW. This is a simple, low-cost, compact, portable, all-fiber ultrafast source for applications requiring environmentally stable, portable sources, such as imaging.

An alternating naphthalene dianhydride bithiophene copolymer (PNDAT2) is prepared by a combined direct arylation polycondensation and the latent pigment approach. PNDAT2 is the first reported example of an alternating conjugated polymer containing naphthalene dianhydride, the oxo-analogue of naphthalene diimide often used in electron-acceptor conjugated polymers. PNDAT2 is resistant to organic solvents and can be generated directly as film by thermal treatment of the soluble tetraester precursor PNTET2. PNDAT2 is characterized by a LUMO level of -3.9 eV, similar to that of established naphthalene diimide containing soluble copolymers. This route to insoluble electron acceptor copolymers by thermal cleavage of soluble precursors is an alternative to classical cross-linking or orthogonal processing strategies.

We combine a graphene mode-locked oscillator with an external compressor and achieve ∼29 fs pulses with ∼52 mW average power. This is a simple, low-cost, and robust setup, entirely fiber based, with no free-space optics, for applications requiring high temporal resolution.

Solution-processed organic semiconductors enable the fabrication of large-area and flexible electronics by means of cost-effective, solution-based mass manufacturing techniques. However, for many applications an insoluble active layer can offer technological advantages in terms of robustness to processing solvents. This is particularly relevant in field-effect transistors (FETs), where processing of dielectrics or barriers from solution on top of the semiconductor layer typically imposes the use of orthogonal solvents in order not to interfere with the nanometer thick accumulation channel. To this end, the use of latent pigments, highly soluble molecules which can produce insoluble films after a post-deposition thermal cleavage of solubilizing groups, is a very promising strategy. In this contribution, we demonstrate the use of tert-butyloxycarbonyl (t-Boc) functionalized diketopyrrolopyrrole and perylene-diimide small molecules for good hole and electron transporting films. t-Boc thermal cleavage leads to densification of the films, along with a strong structural rearrangement of the deprotected molecules, strongly improving charge mobility in both p- and n-type FETs. We also highlight the robustness of these highly insoluble semiconducting layers to typical and aggressive processing solvents. These results can greatly enhance the degree of freedom in the manufacturing of multi-layered organic electronic devices, offering enhanced stability to harsh processing steps.

A solution-processed graphene-film coated on a fiber-based connector is used for stable, mode-locked femtosecond-duration pulses with 16mW average output power.