ABSTRACT Combining UV radiation with vapor phase polymerization (VPP) enables the fabrication of conducting polymer films with tunable electrical, optical, and electrochemical properties. However, traditional mask‐based UV exposure typically requires separation between a photomask and the sample, which limits resolution. This study circumvents this by using a maskless UV exposure system that directly projects high‐resolution patterns onto the substrate. Using poly(3,4‐ethylenedioxythiophene):toluenesulfonate (PEDOT:Tos) as a model material, the resulting minimum feature sizes are approximately 8 µm—nearly half of what has been achieved using mask‐based systems. We find that the obtained resolution is not limited by the optics but is related to material aspects such as molecular diffusion, providing guidelines for further optimizations. Our findings also show that the total delivered dose, rather than exposure time or irradiance, controls the film properties. The resulting PEDOT:Tos patterns exhibit distinct, stable color variations during electrochemical switching, highlighting the potential of maskless UV‐VPP for high‐resolution electrochromic displays.

Conducting polymers are important for areas including energy storage, displays, sensors, nanooptics, and bioelectronics. Vapor phase polymerization (VPP) of conducting polymers can provide highly conductive homogenous thin films but was so far reported only for a limited number of materials. Here, we report VPP deposition of the low bandgap conducting polymer poly(thieno[3,4-b]thiophene):tosylate (pT34bT:Tos) and propose an application for dynamic structural coloration. Optimized films show high electrical conductivity of around 750 S cm-1, manifested optically as wide infrared absorption extending beyond 2000 nm. Electrochemical reduction reveals a neutral low bandgap peak around 1030 nm, making pT34bT comparably transparent also in its neutral state as opposed to other common conducting polymers. Moreover, the VPP process allows to spatially control the polymer properties and thickness via a UV exposure step before polymerization. We exploit this technique to create structurally colored images using the polymer as cavity spacer layer, locally varying its thickness and optical properties. We finally demonstrate dynamic tunability of structural colors based on the application of different potentials in an electrochemical cell.

Nanoparticles have become versatile assets in the medical field, providing notable benefits across diverse medical arenas including controlled drug delivery, imaging, and immunological assays. Among these, non-lamellar lipid nanoparticles, notably cubosomes and hexosomes, showcase remarkable biocompatibility and stability, rendering them as optimal choices for theranostic applications. Particularly, incorporating edge activators like sodium taurocholate enhances the potential of these nanoparticles for dermal and transdermal drug delivery, overcoming the stratum corneum, a first line of defense in our skin. This study reports on the formulation of monoolein-based cubosomes and hexosomes incorporating taurocholate and stabilized by Span 80 and co-encapsulating Chlorin e6 and coenzyme QH for photodynamic therapy in skin metastatic melanoma. The formulations were optimized using small-angle X-ray scattering, and cryo-transmission electron microscopy confirmed the presence of cubosomes or hexosomes, depending on the ratio between taurocholate and Span 80. Furthermore, the co-loaded nanoparticles exhibited high encapsulation efficiencies for both Ce6 and the coenzyme QH. In vitro studies on human melanoma cells (Me45) demonstrated the biocompatibility and photodynamic activity of the loaded formulations. These findings show the possibility of formulating more biocompatible cubosomes and hexosomes for photodynamic therapy in skin cancer treatment.

Chiral-specific interaction of light with organic materials is important but typically arises from circular polarization-dependent absorption of specific optical transitions, resulting in narrow effective wavelength ranges. This study presents a scalable and universal concept for broadband circular dichroism (CD) enabled by strained conducting polymer thin films that possess in-plane hyperbolic optical behavior (i.e., optically metallic and dielectric properties along orthogonal directions). It is shown that off-axis stacking of two or more such thin films provides broadband CD that varies with the hyperbolic bandwidth and stacking geometry. By contrast to traditional chiroptical materials, the CD can also be modulated by redox-tuning of the hyperbolic polymer properties, opening for broadband dynamic chiroptical components.

Supported lipid bilayers (SLBs), formed via lipid vesicle adsorption on highly curved silica surfaces, are widely used in biosensor applications and as models for curved cell membranes. However, SLB formation is often hindered on convex structures with radii comparable to the vesicles. In this study, lightguiding semiconductor nanowires (NWs), engineered for fluorescence signal enhancement, were used to compare the kinetics of SLB formation on vertically oriented NWs and planar silica surfaces. Time resolved fluorescence microscopy with single-molecule sensitivity revealed that while vesicle adsorption rates were similar on both surfaces lateral expansion of the SLB was up to three times faster on NWs than on the planar control. This accelerated expansion is attributed to lower energy penalties when SLBs spread along the cylindrical NWs compared with a planar surface, accompanied by accelerated SLB expansion driven by the merging of the SLB with excess lipids from vesicles accumulated on the NWs.

In nature, colors can originate from pigments or structural effects, with the latter producing brilliant hues through the interference of light with nanoscale structures. This study describes a feasible strategy to achieve structurally colored films based on acetylated lignin nanoparticles. Lignin nanoparticles were prepared by using membrane emulsification and subsequently self-assembled into multilayered films on silicon substrates through an evaporative process. These films exhibit vivid structural colors resulting from thin-film interference, with hues that vary with film thickness. Spectroscopic reflectance measurements and structural analysis reveal a wide range of colors spanning across the visible spectrum. The observed colors are ascribed to interference effects and could be modeled using the transfer matrix method. Furthermore, we demonstrate that increasing relative humidity causes clear color shifts associated with reflectance peak position changes.

Passive radiative cooling is emerging as a sustainable strategy to reduce energy consumption by emitting heat directly through Earth's atmospheric transparency window. Here, we demonstrate transparent wood-based biocomposite coatings as an eco-friendly solution for passive radiative cooling under direct sunlight. We fabricated freestanding, micron-thick coatings using wood scaffolds functionalized with ZnO nanoparticles, followed by thiol-ene in situ polymerization to improve transparency and mechanical resilience. These coatings exhibit high visible transparency combined with exceptionally strong mid-infrared emissivity (∼0.95). When applied onto silicon substrates exposed to direct sunlight, ZnO-functionalized coatings effectively lowered the substrate temperature by ∼6-7 °C. This was primarily attributed to enhanced thermal radiation, highlighting their potential for mitigating overheating in solar cells and other sunlight-exposed structures. Additionally, the enhanced mechanical properties of these biocomposites provide versatility for structural and optical applications, positioning them as a cost-effective, bio-based alternative to traditional cooling technologies.

Materials that provide dynamically tunable infrared (IR) response are important for many applications, including active camouflage and thermal management. However, current IR-tunable systems often exhibit limitations in mechanical properties or practicality of their tuning modalities, or require complex and costly fabrication methods. An additional challenge relates to providing compatibility between different spectral channels, such as allowing an object to be reversibly concealed in the IR without making it appear in the visible range. Here, we demonstrate that conducting polymer-cellulose papers, fabricated through a simple and cheap approach, can overcome such challenges. The papers exhibit IR properties that can be electrochemically tuned with large modulation (absolute emissivity modulation of 0.4) while maintaining largely constant response in the visible range. Owing to high ionic and electrical conductivity, the tuning of the top surface can be performed electrochemically from the other side of the paper even at tens of micrometer thicknesses, removing the need for overlaying electrode and electrolyte in the optical beam path. These features enabled a series of electrically tunable IR devices, where we focus on demonstrating dynamic radiative coolers, thermal camouflage, anti-counterfeiting tags, and grayscale IR displays. The conducting polymer-cellulose papers are sustainable, cheap, flexible and mechanically robust, providing a versatile materials platform for active and adaptive IR optoelectronic devices.

α-Synuclein is an intrinsically disordered presynaptic protein associated with Parkinson's disease. The physiological role of α-Synuclein is not fully understood, but the protein is known to interact with lipid membranes. We here study how membrane charge affects the adsorption of α-Synuclein to (i) supported lipid bilayers and (ii) small unilamellar vesicles with varying amounts of anionic lipids. The results showed that α-Synuclein adsorbs onto membranes containing ≥5% anionic phosphatidylserine (DOPS) lipids, but not to membranes containing ≤1% DOPS. The density of adsorbed α-Synuclein increased steadily with the DOPS content up to 20% DOPS, after which it leveled off. The vesicles were saturated with α-Synuclein at a 3–5 times higher protein density compared to the supported bilayers, which suggests that a more deformable membrane binds more α-Synuclein. Altogether, the results show that both membrane charge density and flexibility influence the association of α-Synuclein to lipid membranes.

Conducting polymers can be dynamically switched between being optically metallic (negative real permittivity) and dielectric (positive real permittivity) by varying their redox state. This has enabled nanoantennas with plasmonic resonances that can be reversibly turned on/off, opening for applications in dynamic metaoptics, reflective displays, and smart windows. However, previous reports on conducting polymer plasmonics were limited to p-type polymers. Here, we show that a highly conducting n-type polymer, called poly(benzodifurandione) (PBFDO), can also provide optically metallic properties and be used to make dynamic optical nanoantennas. The doped version of the polymer becomes metallic at wavelengths above around 700 nm, leading to plasmonic extinction peaks for nanodisks made from the material. These peaks can be reversibly switched off and on electrically or chemically by varying the doping level of the polymer. The study extends the field of dynamic polymer plasmonics to n-type materials and broadens the application areas of PBFDO.

Solar heating is important for many applications but less attractive for concepts requiring intermittent heating, such as ionic thermoelectric supercapacitors (ITESCs). However, the heating process even at constant solar illumination can be converted to temperature oscillations through water infiltration and evaporation. Here, this process is demonstrated for a carbon nanotube-cellulose membrane and used to induce temporally varying temperature gradients across an ITESC, which enables continuous operation through repeated charge and discharge cycles. A temperature variation of 10 K can be generated on the top electrode, which leads to a variation in the temperature difference across the ITESC of 7.5 K. Precise control over charge and discharge durations can be achieved by adjusting the volume and interval of the added water. The concept of temporarily adjusting temperatures by evaporative cooling may be extended to create intermittent heating also for other heat sources that are typically constant. A vertical ionic thermoelectric supercapacitor (ITESC) is driven by intermittent temperature gradients as induced by constant solar heating and periodic evaporative cooling. As shown, a solar absorber provides temperature oscillations on the top electrodes through water infiltration and evaporation. This concept enables continuous operation of ITESCs through repeated charge and discharge cycles. image

Ionic thermoelectric supercapacitors (ITESCs) are noted for their high ionic Seebeck coefficient (α) to convert thermal energy into electrical current through charging. This work demonstrates the utilization of the charging and discharging current from ITESCs to directly operate resistive sensors. The humidity monitoring is powered by applying a periodic temperature gradient to a connected ITESC. By leveraging these properties and residual environmental heat, ITESCs can offer a promising method for autonomously powered portable sensors.

Binding between ligands and receptors across cell contacts influences a range of biological processes including the formation of the immune synapse. The dissociation constant (Kd = 1/affinity) of the interaction corresponds to the concentration of ligands where half of the receptors in the contact have bound a ligand. In this chapter, we outline how to measure this two-dimensional affinity using model cell membranes called supported lipid bilayers (SLBs) functionalized with fluorescently labeled ligands that bind to cells containing the corresponding receptor. The affinity is calculated from the accumulation of ligands at the cell-SLB interface, while the use of different fluorescent tags, and/or unlabeled molecules, makes it possible to include various binding pairs in the contact to better mimic the conditions of binding in vivo.

Ionic thermoelectric materials can generate large thermal voltages under temperature gradients while also being low-cost and environmentally friendly. Many electrolytes with large Seebeck coefficients are reported in recent years, however, the mechanism of the thermal voltage is remained elusive. In this work, three types of polyelectrolytes are studied with different cations and identified a significant contribution to their thermal voltage originating from a concentration gradient. This conclusion is based on studies of the loss and gain of water upon temperature changes, variations in conductivity with water content and temperature, and the voltages induced by changes in water content. The results are analyzed by the "hopping mode" dynamics of charge transport in electrolytes. The hydration of different cations influences the water concentration gradient, which affects the barrier height and ion-induced potential in the electrodes. This work shows that the hydro-voltage in ionic thermoelectric devices can be one order of magnitude larger than the contribution from thermodiffusion-induced potentials, and becomes the main contributor to energy harvesting when implemented into ionic thermoelectric supercapacitors. Together with the rationalized theoretical discussion, this work clarifies the mechanism of thermal voltages in electrolytes and provides a new path for the development of ionic thermoelectric materials. The thermal voltage of polyelectrolyte films largely depends on the water concentration gradient under a temperature difference, which can be optimized to promote the generated total voltage up to over 30 mV K-1.image

Plant vasculature transports molecules that play a crucial role in plant signaling including systemic responses and acclimation to diverse environmental conditions. Targeted controlled delivery of molecules to the vascular tissue can be a biomimetic way to induce long distance responses, providing a new tool for the fundamental studies and engineering of stress-tolerant plants. Here, a flexible organic electronic ion pump, an electrophoretic delivery device, for controlled delivery of phytohormones directly in plant vascular tissue is developed. The c-OEIP is based on polyimide-coated glass capillaries that significantly enhance the mechanical robustness of these microscale devices while being minimally disruptive for the plant. The polyelectrolyte channel is based on low-cost and commercially available precursors that can be photocured with blue light, establishing much cheaper and safer system than the state-of-the-art. To trigger OEIP-induced plant response, the phytohormone abscisic acid (ABA) in the petiole of intact Arabidopsis plants is delivered. ABA is one of the main phytohormones involved in plant stress responses and induces stomata closure under drought conditions to reduce water loss and prevent wilting. The OEIP-mediated ABA delivery triggered fast and long-lasting stomata closure far away from the delivery point demonstrating systemic vascular transport of the delivered ABA, verified delivering deuterium-labeled ABA.

Dynamically tunable reflective structural colors are attractive for reflective displays (electronic paper). However, it is challenging to tune a thin layer of structural color across the full red–green–blue (RGB) basis set of colors at video rates and with long‐term stability. In this work, this is achieved through a hybrid cavity built from metal–insulator–metal (MIM) “nanocaves” and an electrochromic polymer (PProDOTMe 2 ). The reflective colors are modulated by electrochemically doping/dedoping the polymer. Compared with traditional subpixel‐based systems, this hybrid structure provides high reflectivity (>40%) due to its “monopixel” nature and switches at video rates. The polymer bistability helps deliver ultralow power consumption (≈2.5 mW cm −2 ) for video display applications and negligible consumption (≈3 µW cm −2 ) for static images, compatible with fully photovoltaic powering. In addition, the color uniformity of the hybrid material is excellent (over cm −2 ) and the scalable fabrication enables large‐area production.

Photonic films based on cellulose nanocrystals (CNCs) are sustainable candidates for sensors, structurally colored radiative cooling, and iridescent coatings. Such CNC‐based films possess a helicoidal nanoarchitecture, which gives selective reflection with the polarization of the incident light. However, due to the hygroscopic nature of CNCs, the structural colored material changes and may be irreversibly damaged at high relative humidity. Thus, moisture protection is essential in such settings. In this work, hygroscopic CNC‐based films are protected with a bioinspired synthetic plant cuticle; a strategy already adopted by real plants. The protective cuticle layers altered the reflected colors to some extent, but more importantly, they significantly reduced the water vapor permeance by more than two orders of magnitude, from 2.1 × 10 7 (pristine CNC/GLU film) to 12.3 × 10 4 g µm m −2 day −1 atm −1 (protected CNC/GLU film). This expands significantly the time window of operation for CNC/GLU films at high relative humidity.

Abstract Terahertz (THz) technologies provide opportunities ranging from calibration targets for satellites and telescopes to communication devices and biomedical imaging systems. A main component will be broadband THz absorbers with switchability. However, optically switchable materials in THz are scarce and their modulation is mostly available at narrow bandwidths. Realizing materials with large and broadband modulation in absorption or transmission forms a critical challenge. This study demonstrates that conducting polymer‐cellulose aerogels can provide modulation of broadband THz light with large modulation range from ≈ 13% to 91% absolute transmission, while maintaining specular reflection loss < −30 dB. The exceptional THz modulation is associated with the anomalous optical conductivity peak of conducting polymers, which enhances the absorption in its oxidized state. The study also demonstrates the possibility to reduce the surface hydrophilicity by simple chemical modifications, and shows that broadband absorption of the aerogels at optical frequencies enables de‐frosting by solar‐induced heating. These low‐cost, aqueous solution‐processable, sustainable, and bio‐friendly aerogels may find use in next‐generation intelligent THz devices.

Cellulose opens for sustainable materials suitable for radiative cooling thanks to inherent high thermal emissivity combined with low solar absorptance. When desired, solar absorptance can be introduced by additives such as carbon black. However, such materials still shows high thermal emissivity and therefore performs radiative cooling that counteracts the heating process if exposed to the sky. Here, this is addressed by a cellulose-carbon black composite with low mid-infrared (MIR) emissivity and corresponding suppressed radiative cooling thanks to a transparent IR-reflecting indium tin oxide coating. The resulting solar heater provides opposite optical properties in both the solar and thermal ranges compared to the cooler material in the form of solar-reflecting electrospun cellulose. Owing to these differences, exposing the two materials to the sky generated spontaneous temperature differences, as used to power an ionic thermoelectric device in both daytime and nighttime. The study characterizes these effects in detail using solar and sky simulators and through outdoor measurements. Using the concept to power ionic thermoelectric devices shows thermovoltages of >60 mV and 10 °C temperature differences already at moderate solar irradiance of ≈400 W m-2 .