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 cm V s 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.

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 that can be safely ingested, along with pills or even food, and operated from within the gastrointestinal tract. Ingestible electronics can 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. Temporary tattoo-paper is hereby proposed as a simple and versatile platform for the integration of electronics onto food and pharmaceutical capsules. In particular, the fabrication of all-printed organic field-effect transistors on untreated commercial tattoo-paper, and their subsequent transfer and operation on edible substrates with a complex nonplanar geometry is demonstrated.

consumption and sensing as well as high-energy-density batteries for energy storage. Recently, interest in developing systems that interface seamlessly with the human body (e.g., wearables, braincomputer interfaces, and soft robots) has driven the development of soft, organic, and biomimetic materials that emulate the functions of their inorganic counterparts. Beyond emulation, these materials are unique because they provide an opportunity to embody such multifunctional properties within the material itself, rather than relying on device design. These multifunctional properties are intrinsic to organic mixed ionic electronic conductors (OMIECs), that is, once synthesized and processed, OMIECs can serve as the active component of multiple devices (be it transistors, sensors, energy-storage devices, etc.), where essentially the material is the device.OMIECs generally consist of a conjugated backbone for electronic conduction as well as sidechains to facilitate ionic intercalation from the operational electrolyte and to aid in solvation in processing solvents. [1] Organic chemistry provides a large toolbox in the molecular design of the backbone, side chains, and other additives, resulting in an almost infinite design space for the corresponding materials properties: energy levels, electronic and ionic conductivity, optical, volume, and moduli. Additionally, one or more of these properties can be modified during device operation, thereby transducing an input (e.g., ionic) into an output (e.g., electronic), allowing OMIECs to be used for a variety of applications including sensors, transistors, optoelectronic devices, energy-storage electrodes, and actuators. The multifunctionality of OMIECs is illustrated in Figure 1 to highlight their versatility in design and their ability to respond to a variety of stimuli.The underlying and unifying phenomena behind these property changes arise from the large modulation in electronic and ionic charge density in the bulk of the OMIEC. This modulation in turn results in second-order effects such as modulations in electrochemical potential (electron energy levels), electronic and ionic transport, capacitance, free volume, optical bandgap, and modulus. Tuning these properties throughout the bulk of the material enables new design parameters that were previously untapped in traditional electronic devices where Organic mixed ionic-electronic conductors (OMIECs) have gained recent interest and rapid development due to their versatility in diverse applications ranging from sensing, actuation and computation to energy harvesting/ storage, and information transfer. Their multifunctional properties arise from their ability to simultaneously participate in redox reactions as well as modulation of ionic and electronic charge density throughout the bulk of the material. Most importantly, the ability to access charge states with deep modulation through a large extent of its density of states and physical volume of the material enables OMIEC-based devices to display exciting new characteristics...

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 non-invasive 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 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. MAIN TEXTOptical cell viability assay and immunofluorescence staining: The proliferation was evaluated after 1, 2, 3, and 4 d in vitro. For each time point the medium was removed and replaced with RPMI without phenol red containing 0.5 mg mL −1 of MTT reagent (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, Sigma-Aldrich). Cells were reincubated at 37 °C for 3 h. Formazan salt produced by cells through reduction of MTT was then solubilized with 200 mL of ethanol and the absorbance was read at 560 and 690 nm (using a microplate reader TECAN Spark10M). The proliferation cell rate was calculated as the difference in absorbed intensity at 560 and 690 nm. Cells grown on glass coverslips coated with SWCNT networks were washed twice with PBS and fixed for 15 min at RT in 4 % paraformaldehyde and 4 % sucrose in 0.12 M sodium phosphate buffer, pH 7.4. Fixed cells were pre-incubated for 20 min in gelatin dilution buffer (GDB: 0.02 M sodium phosphate buffer, pH 7.4, 0.45 M NaCl, 0.2% (w/v) gelatin) containing 0.3% (v/v)

We combine a graphene mode-locked oscillator with an external compressor and achieve∼29fs pulses with∼52mW 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.Ultrafast light pulses in the femtosecond range are needed for advanced photonics applications. E.g. in pump-probe spectroscopy, photophysical and photochemical relaxation processes are monitored by exciting a sample with an ultrashort light pulse. The maximum temporal resolution is determined by the duration, ∆τ , of the pulse. This is usually defined as the full width at half maximum (FWHM) of its intensity profile in the time domain, I(t) [1]. Alternatively ∆τ may be defined by the number of oscillation periods of the electric field carrier wave (optical cycles) within the pulse[2] N = ∆τ T0 = ν 0 ∆τ , where T 0 is the optical cycle of frequency ν 0 . The ultimate pulse duration is set by a single cycle of light, i.e. T 0 , given by[2] λ c , where λ is the wavelength and c is the speed of light. Finally, the uncertainty relation ∆ν∆τ ≃ 1 π provides a measure of the minimum frequency bandwidth ∆ν required for an ultrashort pulse formation[2], i.e. the broader the bandwidth, the shorter the supported pulse. In the visible and near infrared (NIR), T 0 lies, e.g, between 2fs at λ ∼600nm and 5fs at λ ∼1.5µm, which set the ultimate speed limit for devices operating in this wavelength range. Achieving shorter pulses therefore requires moving to shorter wavelengths.Pulses as short as 2-cycles can be generated directly from laser cavities using passive mode-locking [1][2][3]. Ti:Saphire lasers have become established tools for few-cycle generation [2], with the shortest pulses produced to date having ∆τ ∼5fs[4] at a centre wavelength, λ 0 ∼800nm, corresponding to less than 2-cycles, with spectral width ∆λ ∼600nm [4]. Ti:Saphire lasers able to generate few-cycle durations are typically optimized to make use of the maximum ∆λ gain available[2], consequently they have no wavelength tunability[2]. Tunable Ti:Saphire operate with a much longer pulse duration, e.g. ∆τ ∼150fs in a typical∼680-1080nm commercially available spectral range [5]. Tunable few-cycle pulses can be achieved by exploiting nonlinear optical effects in optical parametric amplifiers (OPAs). These can be described by expressing the polarization (P ) as a power series in the applied optical field (E) [6,7]:, where ǫ 0 is the free space permittivity, χ (1) is the linear and χ (2) and χ (3) are the second-and third-order nonlinear susceptibilities. OPAs are optical amplifiers based on the χ (2) nonlinearity of a crystal [6][7][8], in a process, called parametric [6,7], where there is no net transfer of energy and momentum between E and the crystal [6,7]. This can be visualized, by considering energy transfer from a pump pulse of frequency ω p to two pulses of lower frequencies ω s and ω i , called signal and idler [6,7], with the requirement ω p = ω s + ω i [6,7]. Under this condition, OPAs can...

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.

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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.