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Electroluminescent devices become warm during operation, and their performance can, therefore, be severely limited at high drive current density. Herein, the effects of this self‐heating on the operation of a light‐emitting electrochemical cell (LEC) are systematically studied. A drive current density of 50 mA cm−2 can result in a local device temperature for a free‐standing LEC that exceeds 50 °C within a short period of operation, which in turn induces premature device degradation as manifested in the rapidly decreasing luminance and increasing voltage. Furthermore, this undesired self‐heating for a free‐standing thin‐film LEC can be suppressed by the employment of a device architecture featuring high thermal conductance and a small emission‐area fill factor, since the corresponding improved heat conduction to the nonemissive regions facilitates more efficient heat transfer to the ambient surroundings. In addition, the reported differences in performance between small‐area and large‐area LECs as well as between flexible‐plastic and rigid‐glass LECs are rationalized, culminating in insights that can be useful for the rational design of LEC devices with suppressed self‐heating and high performance., Special Issue: 25 Years of Light‐Emitting Electrochemical Cell Technology

We compare three different methods to quantify the monosaccharide fucose in solutions using the displacement of a large glycoprotein, lactoferrin. Two microfluidic analysis methods, namely fluorescence detection of (labeled) lactoferrin as it is displaced by unlabeled fucose and the displacement of (unlabeled) lactoferrin in SPR, provide fast responses and continuous data during the experiment, theoretically providing significant information regarding the interaction kinetics between the saccharide groups and binding sites. For comparison, we also performed a static displacement ELISA. The stationary binding site in all cases was immobilized S2-AAL, a monovalent polypeptide based on Aleuria aurantia lectin. Although all three assays showed a similar dynamic range, the microfluidic assays with fluorescent or SPR detection show an advantage in short analysis times. Furthermore, the microfluidic displacement assays provide a possibility to develop a one-step analytical platform., Funding Agencies|Health Research Council of Southeast of Sweden [FORSS-389021]; LIST grant from Linkoping University

There is a need for soft actuators in various biomedical applications in order to manipulate delicate objects such as cells and tissues. Soft actuators are able to adapt to any shape and limit the stress applied to delicate objects. Conjugated polymer actuators, especially in the so-called trilayer configuration, are interesting candidates for driving such micromanipulators. However, challenges involved in patterning the electrodes in a trilayer with individual contact have prevented further development of soft micromanipulators based on conjugated polymer actuators. To allow such patterning, two printing-based patterning techniques have been developed. First an oxidant layer is printed using either syringe-based printing or micro-contact printing, followed by vapor phase polymerization of the conjugated polymer. Sub-millimeter patterns with electronic conductivities of 800 Scm-1 are obtained. Next, laser ablation is used to cleanly cut the final device structures including the printed patterns, resulting in fingers with individually controllable digits and miniaturized hands. The methods presented in this paper will enable integration of patterned electrically active conjugated polymer layers in many types of complex 3-D structures., Funding agencies:This study was financially supported by Linköping University, COST Action MP1003 ESNAM (European Scientific Network for Artificial Muscles), the Swedish Research Council (VR – 2010-6672, 2014-3079, 2015-03298), the Knut & Alice Wallenberg Stiftelse (LiU-2010-00318 & LiU-2012- 01361), and the EU FP7 Marie Curie action IEF (625923 POLYACT)

A large-area, fabric-like pump would potentially have applications, for example, in controlling water transport through a garment, such as a rain jacket, regardless of the external temperature and humidity. This paper presents an all-plastic, flexible electroosmotic pump, constructed from commercially available materials: A polycarbonate membrane combined with the electrochemically active polymer poly(3,4-ethylenedioxythiophene) polystyrene sulfonate that actively transports water using an electric potential that can be supplied by a small battery. By using electrochemically active polymer electrodes instead of metal electrodes, the electrochemical reaction that drives flow avoids the oxygen and hydrogen gas production or pH changes associated with water electrolysis. We observe a water mass flux up to 23 mg min(-1) per cm(2) polycarbonate membrane (porosity 10-15%), at an applied potential of 5 V, and a limiting operating pressure of 0.3 kPa V-1, similar to previously reported membrane-based electroosmotic pumps., Funding Agencies|Swedish Research Council (Vetenskapsradet) Grant [2015-03298]

Electroosmotic pumps employing silica frits synthesized from potassium silicate as a stationary phase show strong electroosmotic flow velocity and resistance to pressure-driven flow. We characterize these pumps and measure an electroosmotic mobility of 2.5x10(-8) m(2)/V s and hydrodynamic resistance per unit length of 70 x10(17) Pa s/m(4) with a standard deviation of less than 2% even when varying the amount of water used in the potassium silicate mixture. Furthermore, we demonstrate the simple integration of these pumps into a proofof- concept PDMS lab-on-a-chip device fabricated from a 3D-printed template., Funding Agencies|Vetenskapsradet [2007-3983, 2008-7537, 2011-6404]

Syringe-based 3D-printing is a powerful additive manufacturing method for fabricating short runs (small volumes) of components from multiple materials with a wide range of viscosities. However, objects that are hollow or not in complete contact with the printer’s stage are difficult to fabricate. Using a sacrificial template as a supporting layer enables bottom-up construction of complex structures. Template materials based on polyethylene glycol (PEG) plasticized with organic carbonates to tune their rheological (shear-thinning) and thermal (crystallization) properties have been evaluated, including results from rheometry, differential scanning calorimetry, dissolution rate, chemical compatibility with polydimethylsiloxane (PDMS), and general functionality in a syringe-based 3D-printer. A family of such blends yields material that is easily printed, is stable over time, is soluble in water, and can support other materials and larger structures without collapsing. These mixtures are proposed for use with other extrudable or mouldable materials to enable 3D-printed devices with complex unsupported geometries.

Electroosmotic pumps employing potassium silicate as a stationary phase show strong electroosmotic flow velocity and resistance to pressure-driven flow. We characterize these pumps and demonstrate their simple integration into proof-of-concept PDMS lab-on-a-chip devices fabricated from 3D-printed templates.

In nearly all cases, electrophoresis in gels is driven via the electrolysis of water at the electrodes, where the process consumes water and produces electrochemical by-products. We have previously demonstrated that p-conjugated polymers such as poly(3,4-ethylenedioxythiophene) (PEDOT) can be placed between traditional metal electrodes and an electrolyte to mitigate electrolysis in liquid (capillary electroosmosis/electrophoresis) systems. In this report, we extend our previous result to gel electrophoresis, and show that electrodes containing PEDOT can be used with a commercial polyacrylamide gel electrophoresis system with minimal impact to the resulting gel image or the ionic transport measured during a separation.

Macroporous gelatin beads (CultiSpher™ microcarriers) provide a convenient method for rapidly and reliably introducing cells cultured ex situ into a microfluidic device, where the spheres create a 3D environment for continued cell proliferation. We demonstrate the usefulness of this technique with a proof-of-concept viability analysis of cardiac cells after treatment with doxorubicin. © 2014 the Partner Organisations., AcknowledgementsThe primary embryonic cardiomyocytes were provided byJordi Altimiras, Department of Physics, Chemistry andBiology, Linköping University. The authors thank the SwedishResearch Council (Vetenskapsrådet) for fundingviagrants 2008-7537 and 2011-6404

In addition to its fascinating electrical and mechanical properties, graphene is also an electrochemically stable and transparent electrode material. We demonstrate its applicability as both anode and cathode in a light-emitting electrochemical cell (LEC), an electrochemical analogue to a polymer organic light-emitting diode. Specifically, we summarize recent progress in carbon-based metal-free light-emitting devices enabled by chemically derived graphene cathodes on quartz and plastic substrates, and explain the advantages of using LECs in manufacturing large-area devices.

Lab-on-a-chip detection of fluorescence transduced chemical stimuli is demonstrated using fluidics and optical coupling disposable elements in a configuration compatible with distributed diagnosis. Disposable optical elements are designed to separate excitation by total internal reflection using regular glass slides as optical light guide and fluidics support, while high dynamic range image acquisition with consumer cameras complement the platform to support a broad range of responses with a same configuration. Complementary tone mapping procedures are introduced to systematically double the sensitivity for selected range intervals. Chemical sensitization to free fucose, a diagnostic marker for liver cirrhosis and several cancer forms, illustrates the platform capabilities for diagnosis targets.

We report flexible and metal-free light-emitting electrochemical cells (LECs) using exclusively solution-processed organic materials and illustrate interesting design opportunities offered by such conformable devices with transparent electrodes. Flexible LEC devices based on chemically derived graphene (CDG) as the cathode and poly(3,4-ethylenedioxythiophene) mixed with poly(styrenesulfonate) as the anode exhibit a low turn-on voltage for yellow light emission (V = 2.8 V) and a good efficiency 2.4 (4.0) cd/A at a brightness of 100 (50) cd/m2. We also find that CDG is electrochemically inert over a wide potential range (+1.2 to −2.8 V vsferrocene/ferrocenium) and exploit this property to demonstrate planar LEC devices with CDG as both the anode and the cathode.

Direct current electrokinetic systems generally require Faradaic reactions to occur at a pair of electrodes to maintain an electric field in an electrolyte connecting them. The vast majority of such systems, e. g. electrophoretic separations (capillary electrophoresis) or electroosmotic pumps (EOPs), employ electrolysis of the solvent in these reactions. In many cases, the electrolytic products, such as H+ and OH- in the case of water, can negatively influence the chemical or biological species being transported or separated, and gaseous products such as O-2 and H-2 can break the electrochemical circuit in microfluidic devices. This article presents an EOP that employs the oxidation/reduction of the conjugated polymer poly(3,4-ethylenedioxythiophene), rather than electrolysis of a solvent, to drive flow in a capillary. Devices made with poly(3,4-ethylenedioxythiophene) electrodes are compared with devices made with Pt electrodes in terms of flow and local pH change at the electrodes. Furthermore, we demonstrate that flow is driven for applied potentials under 2 V, and the electrodes are stable for potentials of at least 100 V. Electrochemically active electrodes like those presented here minimize the disadvantage of integrated EOP in, e. g. lab-on-a-chip applications, and may open new possibilities, especially for battery-powered disposable point-of-care devices.

The emerging field of “organic” or “plastic” electronics has brought low-voltage, ultrathin, and energy-efficient lighting and displays to market as organic light-emitting diode (OLED) televisions and displays in cameras and mobile phones. Despite using carbon-based materials as the light-emitting layer, previous efficient organic electronic light-emitting devices have required at least one metal electrode. Here, we utilize chemically derived graphene for the transparent cathode in an all-plastic sandwich-structure device, similar to an OLED, called a light-emitting electrochemical cell (LEC). Using a screen-printable conducting polymer as a partially transparent anode and a micrometer-thick active layer solution-deposited from a blend of a light-emitting polymer and a polymer electrolyte, we demonstrate a light-emitting device based solely on solution-processable carbon-based materials. Our results demonstrate that low-voltage, inexpensive, and efficient light-emitting devices can be made without using metals. In other words, electronics can truly be “organic”.

We report flexible and metal free light-emitting electrochemical cells (LECs) using exclusively solution processed organic materials and illustrate interesting design opportunities offered by such conformable devices with transparent electrodes. Flexible LEC devices based on chemically derived graphene (COG) as the., cathode and poly(3,4-ethylenedioxythiophene) mixed with poly(styrenesulfonate) as the anode exhibit a low turnon voltage for yellow light emission (V = 2.8 V) and a good efficiency 2.4 (4.0) cd/A at a brightness of 100 (50) cd/m(2). We also find that COG is electrochemically inert over a wide potential range (+1.2 to -2.8 V vs ferrocene/ferrocenium) and exploit this property to demonstrate planar LEC devices with COG as both the anode and the cathode.

In the literature there are several methods for electronically guiding aqueous samples through capillary systems such as electrowetting or using various sorts of mechanical valves. Electrowetting typically requires rather large voltages to be applied to the sample itself, which can cause unwanted reactions in the sample. In the current paper the pre-programming the surface energy of a conjugated polymer is presented as a method to eliminate this risk. We found also that mechanical valves, such as pneumatic, magnetic, or based on electroactive polymers are all considerably more difficult to manufacture than the devices presented in this work. Our experiments show that electrochemically modifying the redox state of several conjugated polymers can be used to control the surface energy of the polymers surface. The materials involved lend themselves to low-cost manufacturing, making disposable devices for applications such as in-home medical diagnostics plausible.

Static p-n junctions in inorganic semiconductors are exploited in a wide range of todays electronic appliances. Here, we demonstrate the in situ formation of a dynamic p-n junction structure within an organic semiconductor through electrochemistry. Specifically, we use scanning kelvin probe microscopy and optical probing on planar light-emitting electrochemical cells (LECs) with a mixture of a conjugated polymer and an electrolyte connecting two electrodes separated by 120 mu m. We find that a significant portion of the potential drop between the electrodes coincides with the location of a thin and distinct light-emission zone positioned andgt;30 mu m away from the negative electrode. These results are relevant in the context of a long-standing scientific debate, as they prove that electrochemical doping can take place in LECs. Moreover, a study on the doping formation and dissipation kinetics provides interesting detail regarding the electronic structure and stability of the dynamic organic p-n junction, which may be useful in future dynamic p-n junction-based devices., Original Publication: Piotr Matyba, Klara Maturova, Martijn Kemerink, Nathaniel D Robinson and Ludvig Edman, The dynamic organic p-n junction, 2009, NATURE MATERIALS, (8), 8, 672-676. http://dx.doi.org/10.1038/NMAT2478 Copyright: Nature Publishing Group http://npg.nature.com

Polymer light-emitting electrochemical cells (LECs), the electrochemical analog of light-emitting diodes, are relatively simple to manufacture yet difficult to understand. The combination of ionic and electronic charge carriers make for a richly complex electrochemical device. This paper addresses two curious observations from wide-gap planar LEC experiments: (1) Both the current and light intensity continue to increase with time long after the p-n junction has formed. (2) The light-emitting p-n junction often moves, both "straightening out" and migrating toward the cathode, with time. We propose that these phenomena are explained by the continuation of electrochemical doping even after the p-n junction has formed. We hope that this understanding will help to solve issues such as the limited lifetime of LECs and will help to make them a more practical device in commercial and scientific applications., Original Publication:Nathaniel D Robinson, Junfeng Fang, Piotr Matyba and Ludvig Edman, Electrochemical doping during light emission in polymer light-emitting electrochemical cells, 2008, PHYSICAL REVIEW B, (78), 24, 245202.http://dx.doi.org/10.1103/PhysRevB.78.245202Copyright: American Physical Societyhttp://www.aps.org