Impact of Processing Parameters on Contactless Emulsification via Corona Discharge.

A contactless emulsification method is presented using corona discharge. The corona discharge forms using a pin-to-plate configuration, creating a non-uniform electric field. This results in a simultaneous electrohydrodynamic (EHD) pumping of silicone oil and an electroconvection of water droplets that accelerate and submerge inside the oil, leading to a continuous water-in-oil (W/O) emulsion formation process. The impact of the oil viscosity and corona generating AC and DC electric fields (i.e., voltage and frequency) on the characteristics of the emulsions is studied. The emulsification power consumption using the AC and DC electric fields is calculated and compared to traditional emulsion formation methods. While using the DC electric field results in the formation of uniform emulsions, the AC electric field is readily available and uses less power for the emulsification. This is facile, contactless, and energy-efficient for the continuous formation of W/O emulsions.

Contactless Method of Emulsion Formation Using Corona Discharge.

Electroemulsification methods use electrohydrodynamic (EHD) forces to manipulate fluids and droplets for emulsion formation. Here, a top-down method is presented using a contactless corona discharge for simultaneous emulsion formation and its pumping/collection. The corona discharge forms using a sharp conductive electrode connected to a high-voltage source that ionizes water vapor droplets (formed by a humidifier) and creates an ionic wind (electroconvection), dragging them into an oil medium. The nonuniform electric field induced by the corona discharge also drives the motion of the oil medium via an EHD pumping effect utilizing a modulated bottom electrode geometry. By these two effects, this contactless method enables the immersion of the water droplets into the moving oil medium, continuously forming a water-in-oil (W/O) emulsion. The impact of corona discharge voltage, vertical and horizontal distances between the two electrodes, and depth of the silicone oil on sizes of the formed emulsions is studied. This is a low-cost and contactless process enabling the continuous formation of the W/O emulsions.

Interfacial phenomena in snow from its formation to accumulation and shedding.

Snow accumulation alters the energy budget of engineered (i.e. photovoltaic panels) and natural surfaces (i.e. earth) by affecting the amount of solar energy these surfaces can absorb. Falling of accumulated snow from overhead structures (i.e. telecommunication towers, power lines, wind turbines, and bridge cables) and slipping pedestrians and vehicles on surfaces covered with snow and ice can lead to injuries and safety issues. This review article aimed to provide an overview of snow from its nucleation/formation fundamentals to its interaction with man-made and natural surfaces leading to its accumulation, followed by its removal via shedding and/or melting. Mechanical, thermal, and thermodynamics properties of snow were reviewed providing insights on their impact on snow interaction with surfaces. Finally, currently-available active and passive techniques to mitigate issues associated with snow accumulation on surfaces were reviewed, and perspectives on challenges ahead were provided.

Contactless Method for Electrocoalescence of Water in Oil.

This paper discusses an experimental approach to study the effects of a contactless method on electrocoalescence of water-in-oil mixture/emulsion. A positive corona discharge is utilized using a sharp conductive needle without direct contact with the mixture/solution to avoid potential corrosion of the electrode. This creates a nonuniform electric field, which is further used for the coalescence of water droplets in the range of micro to macro in oil. Two approaches are employed in this study: qualitative analysis conducted by visually studying coalescence patterns in videos captured with a high-speed camera and a quantitative analysis based on calculations obtained from dynamic light scattering measurements. From the behavior of the water droplets under the electric field, it is observed that dipole-dipole interaction, migratory coalescence/electrophoresis, and dielectrophoresis have major roles in promoting the coalescence events. The effects of oil viscosity and power consumption on the coalescence rate are also investigated, suggesting an optimal oil-water separation process. The results of this study pave a path for developing a safe, contactless, rapid, and low-power-consuming separation process, potentially suitable for an offsite application.

Universal Strain Energy-Mediated Dynamic Porosity in Physically Networked Elastomers and Their Applications.

Mechanical and physical properties of porous polymers are highly dependent on the arrangement of their internal pores, which once synthesized are widely considered static. However, here we introduce an unconventional dynamic porosity strategy in physically networked elastomer polymers, irrespective of their chemistry. This strategy allows for an omnidirectional and reversible reconfiguration of porosity in response to applied mechanical deformations, even at ambient conditions. In particular, the normal contact pressure between human fingers (just 0.62 MPa) applied on thin elastomer films results in a permanent reversion of the pores to a denser and more solid state. The porous-to-solid transition leads to a 3 order of magnitude reduction in pore density and up to a 22% relative volumetric shrinkage of the films, resulting in an opaque-to-transparent transition (OTT) that acts as a visual indication of porosity state (porous vs nonporous). It is shown that the pore reversion pressure onset is dependent on the average pore-to-pore distance that is controllable through process-specific parameters. Furthermore, the porosity transition is reversible for multiple cycles when the through-plane compression activation is coupled with an in-plane stretch (ε = 700%). A strain energy-mediated thermodynamic model is successfully implemented to confirm the effects of mechanical deformations on pore reversion and generation. Finally, applications of the newfound dynamic porosity concept are exploited for pressure indication, on-demand modulation of materials' mechanical and thermal characteristics, and flexible photomasks.

Optimum Operating Frequency for Electrocoalescence Induced by Pulsed Corona Discharge.

Current oil-water separation methods require a significant power, a high processing time, and costly equipment, which typically yield low treatment efficiency. Pulsed direct current (dc) electric fields and recently nonuniform electric fields caught considerable attention in the petroleum industry research in order to address the most common oil-water separation issues such as chain formation, partial coalescence, and low efficiency in either the energy consumption or coalescence rate. Here, a contact-less charge injection method induced by corona discharge is utilized to investigate the impacts of nonuniform and pulsed dc electric fields on the coalescence of water droplets inside an oil medium. The operating process parameters were experimentally calibrated and optimized with the goal of increasing the effectiveness and energy consumption efficiency of the coalescence process. High-speed imaging and image processing techniques were used in order to investigate the effect of different active forces (i.e., dipole-dipole interaction, migratory coalescence, or electrophoresis, and dielectrophoresis) during the coalescence process. Different pulsed dc frequencies and pure dc waveforms were utilized and their impact on the coalescence of water droplets was investigated. An optimal coalescence recipe was proposed by continuous measurement of the distance, velocity, and acceleration of the coalescing water droplets. The results of this study suggest use of pulsed dc and pure dc electric fields for coalescence of water droplets in concentrated and dispersed emulsions, respectively.

Delayed Frost Growth on Nanoporous Microstructured Surfaces Utilizing Jumping and Sweeping Condensates.

Self-propelled jumping of condensate droplets (dew) enables their easy and efficient removal from surfaces and is essential for enhancing the condensation heat transfer coefficient and for delaying the frost growth rate on supercooled surfaces. Here, we report the droplet-jumping phenomenon using nanoporous vertically aligned carbon nanotube (VA-CNT) microstructures grown on smooth silicon substrates and coated with poly-(1H, 1H, 2H, 2H-perfluorodecylacrylate) (pPFDA). We also report droplet-sweeping phenomenon on horizontally mounted surfaces, concluding that the frost surface coverage area and the frost growth rates observed with the droplet-sweeping phenomenon are much lower than those that are observed with the droplet-jumping phenomenon alone. We also investigate the fundamentals of droplet-jumping and the frost growth phenomena using line-shaped, hollow-cylindrical, and cylindrical microstructures, comparing the frost surface coverage area and the ice-bridging times during condensation-frosting, prolonged condensation-frosting, and direct-frosting. We find that the closely spaced thin line-shaped microstructures and hollow-cylindrical microstructures are optimal for frost coverage reduction because of their ability to exhibit droplet-jumping and droplet-sweeping phenomena. We observe that adding nonuniform roughness on top of the microstructures leads to jumping-associated droplet-sweeping on supercooled surfaces. Here, we report the evaporation of an already frozen droplet because of freezing of a supercooled condensate droplet in its close vicinity, enabling the Cassie-Baxter state frost growth and enhancing defrosting efficiency. Finally, we discuss the dynamic defrosting behavior of the pPFDA-coated VA-CNT microstructures, concluding that the small gaps (spacings) between the microstructures not only enable dewetting transitions of droplets but also promote the Cassie-Baxter state frost formation.

Dynamics of Liquid Transfer from Nanoporous Stamps in High-Resolution Flexographic Printing.

Printing of ultrathin layers of polymeric and colloidal inks is critical for the manufacturing of electronics on nonconventional substrates such as paper and polymer films. Recently, we found that nanoporous stamps overcome key limitations of traditional polymer stamps in flexographic printing, namely, enabling the printing of ultrathin nanoparticle films with micron-scale lateral precision. Here, we study the dynamics of liquid transfer between nanoporous stamps and solid substrates. The stamps comprise forests of polymer-coated carbon nanotubes, and the surface mechanics and wettability of the stamps are engineered to imbibe colloidal inks and transfer the ink upon contact with the target substrate. By high-speed imaging during printing, we observe the dynamics of liquid spreading, which is mediated by progressing contact between the nanostructured stamp surface and by the substrate and imbibition within the stamp-substrate gap. From the final contact area, the volume of ink transfer is mediated by rupture of a capillary bridge; and, after rupture, liquid spreads to fill the area defined by a precursor film matching the stamp geometry with high precision. Via modeling of the liquid dynamics, and comparison with data, we elucidate the scale- and rate-limiting aspects of the process. Specifically, we find that the printed ink volume and resulting layer thickness are independent of contact pressure; and that printed layer thickness decreases with retraction speed. Under these conditions, nanoparticle films with controlled thickness in the <100 nm regime can be printed using nanoporous stamp flexography, at speeds commensurate with industrial printing equipment.

Explaining Evaporation-Triggered Wetting Transition Using Local Force Balance Model and Contact Line-Fraction.

Understanding wettability and mechanisms of wetting transition are important for design and engineering of superhydrophobic surfaces. There have been numerous studies on the design and fabrication of superhydrophobic and omniphobic surfaces and on the wetting transition mechanisms triggered by liquid evaporation. However, there is a lack of a universal method to examine wetting transition on rough surfaces. Here, we introduce force zones across the droplet base and use a local force balance model to explain wetting transition on engineered nanoporous microstructures, utilizing a critical force per unit length (FPL) value. For the first time, we provide a universal scale using the concept of the critical FPL value which enables comparison of various superhydrophobic surfaces in terms of preventing wetting transition during liquid evaporation. In addition, we establish the concept of contact line-fraction theoretically and experimentally by relating it to area-fraction, which clarifies various arguments about the validity of the Cassie-Baxter equation. We use the contact line-fraction model to explain the droplet contact angles, liquid evaporation modes, and depinning mechanism during liquid evaporation. Finally, we develop a model relating a droplet curvature to conventional beam deflection, providing a framework for engineering pressure stable superhydrophobic surfaces.

Micro-/Nanoscale Approach for Studying Scale Formation and Developing Scale-Resistant Surfaces.

Blockage of pipelines due to accretion of salt particles is detrimental in desalination and water-harvesting industries as they compromise productivity, while increasing maintenance costs. We present a micro-/nanoscale approach to study fundamentals of scale formation, deposition, and adhesion to engineered surfaces with a wide range of surface energies fabricated using the initiated chemical vapor deposition method. Silicon wafers and steel substrates are coated with poly(1 H,1 H,2 H,2 H-perfluorodecylacrylate) or pPFDA, poly(tetravinyl-tetramethylcyclotetrasilohexane) or pV4D4, poly(divinylbenzene) or pDVB, poly(1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasilohexane) or pV3D3, and cross-linked copolymers of poly(2-hydroxyethylmethacrylate) and poly(ethylene glycol) diacrylate or p(PHEMA- co-EGDA). Particles of salt (CaSO4·2H2O) are formed and shaped with a focused ion beam and adhered to a tipless cantilever beam using a micromanipulator setup to study their adhesion strength with a molecular force probe (MFP). Adhesion forces were measured on the substrates in wet and dry conditions to evaluate the effects of interfacial fluid layers and capillary bridges on net adhesion strength. The adhesion between salt particles and the pPFDA coatings decreased by 5.1 ± 1.15 nN in wet states, indicating the influence of capillary bridging between the particle and the liquid layer. In addition, scale nucleation and growth on various surfaces is examined using a quartz crystal microbalance (QCM), where supersaturated solution of CaSO4·2H2O is passed over bare and polymer-coated quartz substrates while mass gain is measured in real time. The salt accretion decreased by 2 folds on pPFDA-coated substrates when compared to that on p(HEMA- co-EGDA) coatings. Both MFP and QCM studies are essential in studying the impact of surface energy and roughness on the extent of scale formation and adhesion strength. This study can pave way for the design of scale-resistant surfaces with potential applications in water treatment, energy harvesting, and purification industries.

Effect of superamphiphobic macrotextures on dynamics of viscous liquid droplets.

The ability of hydrophobic surfaces to repel impinging liquid droplets is important in applications ranging from self-cleaning of solar panels to avoiding ice formation in freezing rain environments. In quest of maximizing water repellency, modification of droplet dynamics and subsequent reduction of contact time have been achieved by incorporating macrotexture on the superhydrophobic surfaces. However, the dynamics of low temperature water, and other viscous liquid droplets impacting anti-wetting surfaces with macrotextures is not well explored. Here, we investigate the effect of viscosity on the bouncing dynamics of liquid droplets impacting macrotextured superamphiphobic surfaces using various glycerol-water mixtures as model liquids at different impacting conditions. We demonstrate that the changes of reduction in contact times by macrotextures due to the increasing viscosity are in opposite trends at low and at high impact velocities. Since macrotexture executes substantial contact time reduction for the droplets which exhibit splitting after the impact, a preliminary model for predicting the minimum impact velocity to observe droplet splitting by macrotexture is proposed considering the important parameters of an impinging droplet along with the surface characteristics and the macrotexture size. This work aims to provide an insight on several possible outcomes of viscous droplets impacting on the macrotextured surfaces and a model that will help to design the desired superamphiphobic surfaces capable of exhibiting reduced contact time and enhanced repellency of low-temperature water droplets (such as freezing rain) and other viscous liquids (such as oils) under different impacting conditions.

Scalable and durable polymeric icephobic and hydrate-phobic coatings.

Ice formation and accumulation on surfaces can result in severe problems for solar photovoltaic installations, offshore oil platforms, wind turbines and aircrafts. In addition, blockage of pipelines by formation and accumulation of clathrate hydrates of natural gases has safety and economical concerns in oil and gas operations, particularly at high pressures and low temperatures such as those found in subsea or arctic environments. Practical adoption of icephobic/hydrate-phobic surfaces requires mechanical robustness and stability under harsh environments. Here, we develop durable and mechanically robust bilayer poly-divinylbenzene (pDVB)/poly-perfluorodecylacrylate (pPFDA) coatings using initiated chemical vapor deposition (iCVD) to reduce the adhesion strength of ice/hydrates to underlying substrates (silicon and steel). Utilizing a highly-cross-linked polymer (pDVB) underneath a very thin veneer of fluorine-rich polymer (pPFDA) we have designed inherently rough bilayer polymer films that can be deposited on rough steel substrates resulting in surfaces which exhibit a receding water contact angle (WCA) higher than 150° and WCA hysteresis as low as 4°. Optical profilometer measurements were performed on the films and root mean square (RMS) roughness values of Rq = 178.0 ± 17.5 nm and Rq = 312.7 ± 23.5 nm were obtained on silicon and steel substrates, respectively. When steel surfaces are coated with these smooth hard iCVD bilayer polymer films, the strength of ice adhesion is reduced from 1010 ± 95 kPa to 180 ± 85 kPa. The adhesion strength of the cyclopentane (CyC5) hydrate is also reduced from 220 ± 45 kPa on rough steel substrates to 34 ± 12 kPa on the polymer-coated steel substrates. The durability of these bilayer polymer coated icephobic and hydrate-phobic substrates is confirmed by sand erosion tests and examination of multiple ice/hydrate adhesion/de-adhesion cycles.

Stable Wettability Control of Nanoporous Microstructures by iCVD Coating of Carbon Nanotubes.

Scalable manufacturing of structured materials with engineered nanoporosity is critical for applications in energy storage devices (i.e., batteries and supercapacitors) and in the wettability control of surfaces (i.e., superhydrophobic and superomniphobic surfaces). Patterns formed in arrays of vertically aligned carbon nanotubes (VA-CNTs) have been extensively studied for these applications. However, the as-deposited features are often undesirably altered upon liquid infiltration and evaporation because of capillarity-driven aggregation of low density CNT forests. Here, it is shown that an ultrathin, conformal, and low-surface-energy layer of poly perfluorodecyl acrylate, poly(1H,1H,2H,2H-perfluorodecyl acrylate) (pPFDA), makes the VA-CNTs robust against surface-tension-driven aggregation and densification. This single vapor-deposition step allows the fidelity of the as-deposited VA-CNT patterns to be retained during wet processing, such as inking, and subsequent drying. It is demonstrated how to establish omniphobicity or liquid infiltration by controlling the surface morphology. Retaining a crust of entangled CNTs and pPFDA aggregates on top of the patterned VA-CNTs produces micropillars with re-entrant features that prevent the infiltration of low-surface-tension liquids and thus gives rise to stable omniphobicity. Plasma treatments before and after polymer deposition remove the crust of entangled CNTs and pPFDA aggregates and attach hydroxyl groups to the CNT tips, enabling liquid infiltration yet preventing densification of the highly porous CNTs. The latter observation demonstrates the protective character of the pPFDA coating with the potential application of these surfaces for direct contact printing of microelectronic features.

CVD Polymers for Devices and Device Fabrication.

Chemical vapor deposition (CVD) polymerization directly synthesizes organic thin films on a substrate from vapor phase reactants. Dielectric, semiconducting, electrically conducting, and ionically conducting CVD polymers have all been readily integrated into devices. The absence of solvent in the CVD process enables the growth of high-purity layers and avoids the potential of dewetting phenomena, which lead to pinhole defects. By limiting contaminants and defects, ultrathin (<10 nm) CVD polymeric device layers have been fabricated in multiple laboratories. The CVD method is particularly suitable for synthesizing insoluble conductive polymers, layers with high densities of organic functional groups, and robust crosslinked networks. Additionally, CVD polymers are prized for the ability to conformally cover rough surfaces, like those of paper and textile substrates, as well as the complex geometries of micro- and nanostructured devices. By employing low processing temperatures, CVD polymerization avoids damaging substrates and underlying device layers. This report discusses the mechanisms of the major CVD polymerization techniques and the recent progress of their applications in devices and device fabrication, with emphasis on initiated CVD (iCVD) and oxidative CVD (oCVD) polymerization.

Ultrathin high-resolution flexographic printing using nanoporous stamps.

Since its invention in ancient times, relief printing, commonly called flexography, has been used to mass-produce artifacts ranging from decorative graphics to printed media. Now, higher-resolution flexography is essential to manufacturing low-cost, large-area printed electronics. However, because of contact-mediated liquid instabilities and spreading, the resolution of flexographic printing using elastomeric stamps is limited to tens of micrometers. We introduce engineered nanoporous microstructures, comprising polymer-coated aligned carbon nanotubes (CNTs), as a next-generation stamp material. We design and engineer the highly porous microstructures to be wetted by colloidal inks and to transfer a thin layer to a target substrate upon brief contact. We demonstrate printing of diverse micrometer-scale patterns of a variety of functional nanoparticle inks, including Ag, ZnO, WO3, and CdSe/ZnS, onto both rigid and compliant substrates. The printed patterns have highly uniform nanoscale thickness (5 to 50 nm) and match the stamp features with high fidelity (edge roughness, ~0.2 µm). We derive conditions for uniform printing based on nanoscale contact mechanics, characterize printed Ag lines and transparent conductors, and achieve continuous printing at a speed of 0.2 m/s. The latter represents a combination of resolution and throughput that far surpasses industrial printing technologies.

Polymer Thin Films and Surface Modification by Chemical Vapor Deposition: Recent Progress.

Chemical vapor deposition (CVD) polymerization uses vapor phase monomeric reactants to synthesize organic thin films directly on substrates. These thin films are desirable as conformal surface engineering materials and functional layers. The facile tunability of the films and their surface properties allow successful integration of CVD thin films into prototypes for applications in surface modification, device fabrication, and protective films. CVD polymers also bridge microfabrication technology with chemical and biological systems. Robust coatings can be achieved via CVD methods as antifouling, anti-icing, and antihydrate surfaces, as well as stimuli-responsive or biocompatible polymers and novel nanostructures. Use of low-energy input, modest vacuum, and room-temperature substrates renders CVD polymerization compatible with thermally sensitive substrates and devices. Compared with solution-based methods, CVD is particularly useful for insoluble materials, such as electrically conductive polymers and controllably crosslinked networks, and has the potential to reduce environmental, health, and safety impacts associated with solvents. This review discusses the relevant background and selected applications of recent advances by two methods that display and use the high retention of the organic functional groups from their respective monomers, initiated CVD (iCVD) and oxidative CVD (oCVD) polymerization.

Signature Vibrational Bands for Defects in CVD Single-Layer Graphene by Surface-Enhanced Raman Spectroscopy.

We report the observation of signature vibrational bands in the frequency region between 900 and 1600 cm(-1) for defects in single-layer graphene (SLG) using surface Raman spectroscopy in ultrahigh vacuum. Vapor deposition of Ag leads to the formation of surface nanoparticles that migrate to defects in the SLG, leading to surface-enhanced Raman scattering (SERS) of the graphene G and 2D bands as well as new vibrational modes ascribed to native defects. Many of the new spectral bands of these native defects are similar, although not identical, to those predicted previously for -C2 defects. These new bands are observed in addition to bands more commonly observed for defective graphene that are attributed to the D, G*, D+G, and 2D' modes. The defects observed in these SLG films are not believed to result from the Ag deposition process but are postulated to be formed during the graphene CVD growth process. These defects are then made visible by postdeposition of Ag due to SERS.

Investigation into the Formation and Adhesion of Cyclopentane Hydrates on Mechanically Robust Vapor-Deposited Polymeric Coatings.

Blockage of pipelines by formation and accumulation of clathrate hydrates of natural gases (also called gas hydrates) can compromise project safety and economics in oil and gas operations, particularly at high pressures and low temperatures such as those found in subsea or arctic environments. Cyclopentane (CyC5) hydrate has attracted interest as a model system for studying natural gas hydrates, because CyC5, like typical natural gas hydrate formers, is almost fully immiscible in water; and thus CyC5 hydrate formation is governed not only by thermodynamic phase considerations but also kinetic factors such as the hydrocarbon/water interfacial area, as well as mass and heat transfer constraints, as for natural gas hydrates. We present a macroscale investigation of the formation and adhesion strength of CyC5 hydrate deposits on bilayer polymer coatings with a range of wettabilities. The polymeric bilayer coatings are developed using initiated chemical vapor deposition (iCVD) of a mechanically robust and densely cross-linked polymeric base layer (polydivinylbenzene or pDVB) that is capped with a covalently attached thin hydrate-phobic fluorine-rich top layer (poly(perfluorodecyl acrylate) or pPFDA). The CyC5 hydrates are formed from CyC5-in-water emulsions, and differential scanning calorimetry (DSC) is used to confirm the thermal dissociation properties of the solid hydrate deposits. We also investigate the adhesion of the CyC5 hydrate deposits on bare and bilayer polymer-coated silicon and steel substrates. Goniometric measurements with drops of CyC5-in-water emulsions on the coated steel substrates exhibit advancing contact angles of 148.3 ± 4.5° and receding contact angles of 142.5 ± 9.8°, indicating the strongly emulsion-repelling nature of the iCVD coatings. The adhesion strength of the CyC5 hydrate deposits is reduced from 220 ± 45 kPa on rough steel substrates to 20 ± 17 kPa on the polymer-coated steel substrates. The measured strength of CyC5 hydrate adhesion is found to correlate very well with the work of adhesion between the emulsion droplets used to form the CyC5 hydrate and the underlying substrates.

Creating graphene p-n junctions using self-assembled monolayers.

3-Aminopropyltriethoxysilane (APTES) and perfluorooctyltriethoxysilane (PFES) were used to modify the interface between transferred CVD graphene films and its supporting dielectric to create n-type and p-type graphene, respectively. A graphene p-n junction was obtained by patterning both modifiers on the same dielectric and verified through the creation of a field effect transistor (FET). Characteristic I-V curves indicate the presence of two separate Dirac points which confirms an energy separation of neutrality points within the complementary regions. This method minimizes doping-induced defects and results in thermally stable graphene p-n junctions for temperatures up to 200 °C.

A universal method to produce low-work function electrodes for organic electronics.

Organic and printed electronics technologies require conductors with a work function that is sufficiently low to facilitate the transport of electrons in and out of various optoelectronic devices. We show that surface modifiers based on polymers containing simple aliphatic amine groups substantially reduce the work function of conductors including metals, transparent conductive metal oxides, conducting polymers, and graphene. The reduction arises from physisorption of the neutral polymer, which turns the modified conductors into efficient electron-selective electrodes in organic optoelectronic devices. These polymer surface modifiers are processed in air from solution, providing an appealing alternative to chemically reactive low-work function metals. Their use can pave the way to simplified manufacturing of low-cost and large-area organic electronic technologies.