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International audience; Electrochemical regeneration of the cofactor nicotinamide adenine dinucleotide (NADH) is crucial for the enzymatic synthesis of a variety of valuable chemicals. [Rh(Cp*)(bpy)Cl]+ has been reported as one of the most efficient non-enzymatic catalysts for electrochemical regeneration of NADH, but the efficiency of the existing systems is still far from satisfying. Here we propose to suspend metalorganic framework functionalized glassy carbon beads in a bipolar electrochemical cell under mechanical stirring for bulk electroenzymatic synthesis. The beads are modified with a metal-organic framework NU-1000 shell, in which [Rh(Cp*)(bpy)Cl]+ catalyst is incorporated via the solvent-assisted ligand incorporation approach. Enzymatically active 1,4-NADH is electrochemically regenerated, and finally bipolar electrochemical bulk conversion of pyruvate into L-lactate is performed in the presence of NADH dependent L-lactate dehydrogenase as a model system. The very high turnover frequency (TOF) of 3100±106 h-1 opens up promising perspectives for employing this concept also for various other electroenzymatic bulk processes.

Inserting complex biomolecules such as oligonucleotides during the synthesis of polymers remains an important challenge in the development of functionalized materials. In order to engineer such a biofunctionalized interface, a single-step method for the covalent immobilization of oligonucleotides (ONs) based on novel electropolymerizable lipid thiophene-oligonucleotide (L-ThON) conjugates was employed. Here, we report a new thiophene phosphoramidite building block for the synthesis of modified L-ThONs. The biofunctionalized material was obtained by direct electropolymerization of L-ThONs in the presence of 2,2'-bithiophene (BTh) to obtain a copolymer film on indium tin oxide electrodes.

International audience

International audience; Electrochemistry is taught in most undergraduate chemistry programs. Although this topic is important for students due to its broad interest in industry (energy, diagnostics, car industry, etc.), they often find it difficult, because it is based on a combination of various physical concepts such as electric fields, interfacial processes or charge and mass transports. Among electrochemical concepts, bipolar electrochemistry is of special interest and might be easier to teach due to a very simple general setup. In this case, an oxidation and a reduction reactions occur at the two ends of a single conductive object exposed to an electric field in solution. Such an object is therefore called a bipolar electrode. The nature of the electrochemical reactions and their amplitude can be tuned by playing with the electric field. The fundamental concepts of bipolar electrochemistry are introduced here with a series of basic experiments designed to be carried out in a standard teaching laboratory. These simple and affordable experiments illustrate the key-parameters driving electrochemical reactions at a bipolar electrode. Their influence can be readily visualized using a cheap, commercially available light emitting diode (LED) acting as the bipolar electrode, which illuminates when the current generated by the electrochemical reactions flows through it. The concept of bipolar electrochemistry with eye-catching experiments enables a good introduction to general

Microfluidic valves based on chemically responsive materials have gained considerable attention in recent years. Herein, a wireless enantio-responsive valve triggered by bipolar electrochemistry combined with chiral recognition is reported. A conducting polymer actuator functionalized with the enantiomers of an inherently chiral oligomer was used as bipolar valve to cover a tube loaded with a dye and immersed in a solution containing chiral analytes. When an electric field is applied, the designed actuator shows a reversible cantilever-type deflection, allowing the release of the dye from the reservoir. The tube can be opened and closed by simply switching the polarity of the system. Qualitative results show the successful release of the colorant, driven by chirality and redox reactions occurring at the bipolar valve. The device works well even in the presence of chemically different chiral analytes in the same solution. These systems open up new possibilities in the field of microfluidics, including also controlled drug delivery applications.

International audience; Chiral-imprinted mesoporous Pt-Ir alloy surfaces were combined in a synergetic way with electrochemiluminescence (ECL) to detect the two enantiomers of phenylalanine (PA) as a model compound, acting simultaneously as a chiral target and as a co-reactant to generate significant differences in ECL signals. The chiral features of the metal surfaces are converted into an enantioselective electrogeneration of the excited state of the [Ru(bpy)3]2+ dye, which in fine produces the differentiating light emission with up to 20-fold differences in intensity for the two enantiomers. These findings open up the possibility of developing new ECL-based bioassays and microscopy of chiral environments.

The sustainable conversion of biomass-derived compounds into high added-value products is a very important contemporary scientific challenge. In this context, we report here the simultaneous electro-oxidation/-reduction of a biomass-derived compound in a one-pot approach using bipolar electrochemistry. Bifunctional Pt/Au Janus electrocatalysts are employed for a selective conversion of furfural into both, furfuryl alcohol and furoic acid, which can't be achieved when using non-Janus particles. The results emphasize the benefits of bipolar electrochemistry in the frame of electrosynthesis processes.

International audience; Bipolar electrochemistry is a technique that involves two opposite chemical processes, namely an oxidation and a reduction, occurring simultaneously on the surface of a conducting object, usually without connection to a power supply. The basic phenomenon has already been described and used for many decades but regained a lot of interest in recent years, thanks to several attractive features for developing new applications in various areas ranging from materials science and analytical chemistry to catalysis and even life science. Consequently, bipolar electrochemistry has experienced a substantial growth in the number of users and publications. This is mostly due to several advantages over classic electrochemistry, such as the absence of an ohmic contact, the generation of a directional gradient of electroactivity on the object, and the possibility to address simultaneously thousands of objects, which opens the door for high throughput screening of (electro)chemical properties. Also, some features of this “wireless” electrochemistry allow performing experiments that cannot be achieved with a classic electrochemical set-up. Last but not least, only rather low-cost equipment is needed.The objective of the present contribution is to introduce first some fundamental aspects of bipolar electrochemistry, and then to illustrate its different developments, highlighting not only the historic landmark achievements, but also the most recent findings, especially in the context of micro- and nanoscience. The chapter will illustrate the singularities and advantages of this straightforward approach and hopefully convince the reader of the power of this interesting electrochemical concept.

In situ UV-vis-NIR spectroelectrochemistry has been intensively used to evaluate the electronic transitions during the charging/discharging process of π-conjugated polymers. However, the type of charge carrier and the mechanisms of their transport, remains still a point of discussion. Herein, the coupling between UV-vis-NIR spectroscopy and in situ electrochemical-conductance measurements is proposed to compare the doping process of three different thiophene-based conducting polymers. The simultaneous monitoring of electrical and absorption properties, associated with low energy electronic transitions characteristic for polarons and bipolarons, was achieved. In addition, this method allows evaluating the reversible charge trapping mechanism of poly-3,4-o-xylendioxythiophene (PXDOT), caused by the formation of σ-dimers, making it a very useful tool to determine relevant physicochemical properties of conductive materials.

Redox cycling (RC) is a powerful tool capable of amplifying faradaic currents in electroanalytical measurements, thus allowing an enhancement of sensitivity through fast multiple sequential oxidation and reduction reactions of a redox-active analyte. Present state-of-the-art RC devices are mostly based on planar electrode geometries either in 2D or 3D configurations, requiring cleanroom facilities and expensive microfabrication techniques. Here, the electrochemical elaboration and characterization of a 3D coaxial macroporous twin-electrode is reported, obtained by following a low-cost bottom-up approach. A nanoengineered highly organized porous material is the basis for the design of two threaded cylindrical porous gold microelectrodes with a gap in the micrometer range that can be fine-tuned. The potentials of the outer and inner electrodes are biased at values above and below the redox potential of the analyte so that a given molecule can participate several times in the electron exchange reaction by shuttling between both electrodes. The resulting signal amplification, combined with a straightforward synthesis strategy of the electrode architecture, allows envisioning numerous (bio)electroanalytical applications.

Electrochemical regeneration of the reduced form of the nicotinamide adenine dinucleotide (NADH) cofactor catalyzed by immobilized [Rh(Cp*)(bpy)Cl]

International audience; The development of chiral catalysts plays a very important role in various areas of chemical science. Heterogeneous catalysts have the general advantage of allowing a more straightforward separation from the products. One specific case of heterogeneous catalysis is electrocatalysis, being potentially a green chemistry approach. However, a typical drawback is that the redox conversion of molecules occurs only at the electrode/electrolyte interface, and not in the bulk of the electrolyte. The second limitation is that the electrodes have to be physically connected to a power supply to induce the desired reactions. To circumvent these problems, we propose here a complementary approach by replacing macroscopic electrodes with an ensemble of self-propelled redox active microswimmers. They move autonomously in solution while transforming simultaneously a prochiral starting compound into a specific enantiomer with a very high enantiomeric excess, accompanied by a significantly increased production rate of the favorite enantiomer.

International audience; Straightforward enantioselective analytical methods are very important for drug safety, considering that in certain cases one of the two enantiomers of a chiral molecule might be harmful for humans. In this work, we propose a simple system for the direct and easy read-out of the enantiomeric excess of 3,4-dihydroxyphenylalanine (DOPA) as a model analyte. A conducting oligomer, i.e. oligo-(3,3′-dibenzothiophene), bearing inherently chiral features, is electrogenerated on a polypyrrole film. The resulting freestanding hybrid material is used as a wireless enantioselective actuator in a bipolar electrochemical cell. Combining in a single setup two individual actuators with opposite chiral features allows a direct visual read-out of enantiomeric excess, as the bending amplitude of each of the two actuators is directly correlated with the concentration of the corresponding stereoisomer of the analyte. Optimization of the experimental parameters results in efficient bending, giving access to the percentage values of the enantiomeric excess in mixtures containing different ratios of the antipodes, thus opening the way to potential applications for chiral in situ analysis.

Spatial confinement of chemical reactions or physical effects may lead to original phenomena and new properties. Here, the generation of electrochemiluminescence (ECL) in confined free-standing 2D spaces, exemplified by surfactant-based air bubbles is reported. For this, the ultrathin walls of the bubbles (typically in the range of 100-700 nm) are chosen as a host where graphene sheets, acting as bipolar ECL-emitting electrodes, are trapped and dispersed. The proposed system demonstrates that the required potential for the generation of ECL is up to three orders of magnitude smaller compared to conventional systems, due to the nanoconfinement of the potential drop. This proof-of-concept study demonstrates the key advantages of a 2D environment, allowing a wireless activation of ECL at rather low potentials, compatible with (bio)analytical systems.

International audience; Actuators controlled by external stimuli have received a lot of attention in recent years. Herein we report a polymer based dual stimuli actuator, triggered by light and an electric field. This allows a better control of actuation, enlarging the field of potential applications, like e.g. in the frame of soft robotics. The actuator is composed of polypyrrole (PPy) and TiO2 modified with methylene blue (MB). In aqueous solution, the resulting freestanding hybrid film shows reversible actuation due to the synergy of light and an applied electric field. Illumination with light produces electron-hole pairs in the TiO2 layer, which are shuttled to the opposite ends of the actuator by the potential gradient present in solution. This results in electrochemical oxidation and reduction reactions at the two extremities and consequently in site selective swelling of the polymer, which finally leads to a controlled motion of the actuator, following the principles of logic gate operations. Such synergistically induced switching allows developing original actuation schemes for performing complex mechanical tasks triggered by more than one stimulus.

Objective: Differences in type 2 diabetes phenotype by age are described, but it is not known whether these differences are seen in a more uniformly defined adult population at a common early stage of care. We characterize age-related clinical and metabolic characteristics of adults with type 2 diabetes on metformin monotherapy, prior to treatment intensification. Research Design and Methods: The Glycemia Reduction Approaches in Diabetes: A Comparative Effectiveness (GRADE) Study enrolled participants with type 2 diabetes duration ≥65 years) using ANOVA and Pearson’s chi-squared tests.. Results: Within the GRADE cohort (n=5,047), we observed significant differences by age with younger adults having greater racial diversity, fewer medications for common comorbidities, lower prevalence of CVD, higher weight and BMI, more pronounced hyperglycemia and diabetic dyslipidemia, with metabolic profile indicating lower insulin sensitivity (1/fasting insulin, HOMA-2S, Matsuda index) and inadequate β cell response (oral disposition index) (p < 0.05 across age categories). Conclusions: Clinical and metabolic characteristics of type 2 diabetes differ by age within the GRADE cohort. Younger adults exhibit more prominent obesity-related characteristics, including higher obesity levels, lower insulin sensitivity and beta cell compensation. Given the increasing burden of type 2 diabetes and complications, particularly among younger populations, these age-related distinctions may inform risk factor management approaches and treatment priorities. Further study will determine whether age-related differences impact response to therapy.

International audience; Wireless electrochemical systems constitute a rapidly developing field. Herein, photo-induced electrochemiluminescence (PECL) is studied at Si-based closed bipolar electrodes (BPEs) for designing anti-Stokes systems that can convert IR into visible photons, without direct electrical contact. We show that protection of the anodic emitting pole of the BPE allows the triggering of bright and longstanding emission under the synergetic actions of an external bias and IR illumination. Photoactive nand p-type Si BPEs are studied with front-side and backside illumination, respectively, and non-photoactive n +-Si BPEs are studied in the dark. Two electrochemiluminescent (ECL) systems ([Ru(bpy) 3 ] 2+ /TPrA and L-012) are tested and we show that the onset bias and the anti-Stokes shift can be controlled by the ECL system that is employed. These advances, rationalized by simulations, will be useful for the design of original PECL systems for chemical sensing or photodetection.

Vegetation attenuates the microwave emission from the land surface. The strength of this attenuation is quantified in models in terms of the parameter vegetation optical depth (VOD) and is influenced by the vegetation mass, structure, water content, and observation wavelength. Earth observation satellite sensors operating in the microwave frequencies are used for global VOD retrievals, enabling the monitoring of vegetation at large scales. VOD has been used to determine above-ground biomass, monitor phenology, or estimate vegetation water status. VOD can be also used for constraining land surface models or modelling wildfires at large scales. Several VOD products exist, differing by frequency/wavelength, sensor, and retrieval algorithm. Numerous studies present correlations or empirical functions between different VOD datasets and vegetation variables such as the normalized difference vegetation index, leaf area index, gross primary production, biomass, vegetation height, or vegetation water content. However, an assessment of the joint impact of land cover, vegetation biomass, leaf area, and moisture status on the VOD signal is challenging and has not yet been done. This study aims to interpret the VOD signal as a multi-variate function of several descriptive vegetation variables. The results will help to select VOD at the most suitable wavelength for specific applications and can guide the development of appropriate observation operators to integrate VOD with large-scale land surface models. Here we use VOD from the Land Parameter Retrieval Model (LPRM) in the Ku, X, and C bands from the harmonized Vegetation Optical Depth Climate Archive (VODCA) dataset and L-band VOD derived from Soil Moisture and Ocean Salinity (SMOS) and Soil Moisture Active Passive (SMAP) sensors. The leaf area index, live-fuel moisture content, above-ground biomass, and land cover are able to explain up to 93 % and 95 % of the variance (Nash–Sutcliffe model efficiency coefficient) in 8-daily and monthly VOD within a multi-variable random forest regression. Thereby, the regression reproduces spatial patterns of L-band VOD and spatial and temporal patterns of Ku-, X-, and C-band VOD. Analyses of accumulated local effects demonstrate that Ku-, X-, and C-band VOD are mostly sensitive to the leaf area index, and L-band VOD is most sensitive to above-ground biomass. However, for all VODs the global relationships with vegetation properties are non-monotonic and complex and differ with land cover type. This indicates that the use of simple global regressions to estimate single vegetation properties (e.g. above-ground biomass) from VOD is over-simplistic.

Living systems that can spontaneously exhibit directional motion belong to diverse classes such as bacteria, sperm and plankton. They have fascinated scientists in recent years to design completely artificial or biohybrid mobile objects. Natural ingredients, like parts of plants, have been used to elaborate miniaturized dynamic objects, which can move when they are combined with other, non-natural, building blocks. Herein, we report that the precise structural tailoring of natural plant leaves allows generating a spatially predefined and confined release of oxygen gas, due to the conversion of carbon dioxide. This constitutes the driving force for generating motion, which is solely due to the respiration of leaves by photosynthesis. The rate of gas evolution can be fine-tuned by changing the light intensity and the leaf size, allowing ultimately to control the motility of objects with dimensions ranging from the millimeter to the micrometer scale.

The design of efficient chiral catalysts is of crucial importance since it allows generating enantiomerically pure compounds. Tremendous efforts have been made over the past decades regarding the development of materials with enantioselective properties for various potential applications ranging from sensing to catalysis and separation. Recently, chiral features have been generated in mesoporous metals. Although these monometallic matrices show interesting enantioselectivity, they suffer from rather low stability, constituting an important roadblock for applications. Here, a straightforward strategy to circumvent this limitation by using nanostructured platinum-iridium alloys is presented. These materials can be successfully encoded with chiral information by co-electrodeposition from Pt and Ir salts in the simultaneous presence of a chiral compound and a lyotropic liquid crystal as asymmetric template and mesoporogen, respectively. The alloys enable a remarkable discrimination between chiral compounds and greatly improved enantioselectivity when used for asymmetric electrosynthesis (>95 %ee), combined with high electrochemical stability., Tremendous efforts have been made over the past decades regarding the development of materials with enantioselective properties. Here, the authors present a nanostructured chiral imprinted metal alloy that exhibits high enantioselectivity and stability for the electrosynthesis of chiral molecules.

The electric motor production of the automotive industry faces numerous challenges due to weak sales and uncertain sales forecasts of the electric vehicle. To meet these challenges, scalable production systems have increasingly been set up. The application of virtual commissioning to scalable production systems holds increased potential since the deterministic simulation model can be improved step by step through the inclusion of real data. Therefore, a concrete process model is to be created describing how virtual commissioning can be made even more effective through real data connection. The validation is carried out on an application from material handling technology.

A series of mono-, di-, and tri-topic receptors, in which H-bonding sites, complementary to those of barbituric acid (BA), are fused, is used to induce the supramolecular assembly of n x m ladders containing 1, 2, or 3 triphenylenevinylene units appended with BA. The topological constraint enforced by the architectures induces through-space interactions between the electroactive moieties that are reflected in the electronic absorption and emission spectrum. The n =2, m =2 or m =3 architectures undergo two single electron oxidation events indicative of the formation of the corresponding mono- and di-radical cation species with comproportionation constants of 340 and 70, respectively. Comparison of the electrochemical potentials suggests that the charges are delocalized over the electroactive units in the assembly.

This work is dedicated to a multi-scale modelling of coupled diffusion and reaction in a porous microelectrode operating in the Direct Electron Transfer mode. The pore-scale physico-electrochemical unsteady model is developed considering the oxygen reduction, catalyzed by an enzyme coating the pores of the electrode, coupled to the diffusion of oxygen and mass balance of enzymes. This model is formally upscaled to obtain an original closed unsteady macroscopic model operating at the electrode scale, together with the associated closure providing the effective diffusivity tensor. A validation of this model is carried out from a comparison with the solution of the initial 3D pore-scale governing equations considering the bilirubin oxydase as the catalyst. The relevance and accuracy of the macroscale model are proved allowing a considerable simulation speedup. It is further employed to successfully predict experimental voltammetry results obtained with porous gold electrodes functionnalized with a bilirubin oxidase mutant (BOD S362C). This model represents a breakthrough by providing an operational simple way of understanding and further optimizing porous electrodes functioning in DET mode.

International audience; Conducting polymers have been extensively studied due to their potential applications ranging from sensing to energy storage and environmental remediation. They can be easily generated by electrosynthesis and have also very interesting electrochemical features, which have been mostly examined with classic electrochemical approaches. Bipolar electrochemistry offers an attractive alternative way to synthesize and characterize the physico-chemical properties of conducting polymers. The wireless and asymmetric features of bipolar electrochemistry can be advantageously combined with the electroactivity, tunability and easy processability of conducting polymers. This synergy has been increasingly explored in recent years for the controlled electrogeneration, surface modification and characterization of different π-conjugated polymers. This review summarizes the advances in this context and discusses also some unconventional applications such as wireless light-emitting devices and actuators.

International audience; Chirality governs many chemical and biological processes, since most active substances are chiral. Enantiomers are mirror images of the same molecule that can exhibit significant differences in terms of biochemical activity, toxicity and transport mechanisms in the human body. Thus, developing effective methods to achieve chiral recognition is of great significance and has been a hot topic in chemo/biological studies. In recent years, electrochemical methods have received considerable attention in this field since they can offer several advantages over chromatographic or spectroscopic methods. In this review, a comprehensive and critical description of the trends in electrochemical chiral recognition over the last five years is presented. In addition, some unconventional electrochemical methods for the transduction of chirality at different length scales are described and discussed.

International audience; Bipolar electrochemistry can be employed in the context of chiral recognition in order to obtain useful analytical readouts of enantiomeric analytes. Herein, we employ this concept for the simultaneous determination of two enantiomers present in solution, and its possible use as transduction mechanism for complex real matrices analysis. This approach is based on the combination of the enantioselective electrooxidation of only one of the two antipodes of a chiral analyte with the emission of light from light-emitting diodes (LEDs). A double hybrid device was designed, using the enantiomers of an inherently chiral oligomer and a bare gold wire as the anode and cathode of a green and red LED. By applying an appropriate voltage, the wirelessly induced redox reactions trigger light emission only when the probe with the right configuration is present in solution. This device was used to simultaneously measure the ratio between Land D-Tryptophan, both present in the same solution and to quantify L-ascorbic acid in a commercial juice sample. The measurement correlates with the value reported on the sample specifications. These results illustrate the possible use of such light emitting bipolar devices as analytical tools for qualitative and quantitative measurements of enantiomeric excess, even in real samples.

In this work, bipolar electrochemistry is used to perform wireless indirect electrodeposition of two different polymer coatings on both sides of carbon nanotube arrays. Using a thermoresponsive hydrogel on one side and an inert insoluble polymer on the other side, it is possible to generate, in a single step, a nanoporous reservoir with Janus character closed on one side by a thermoresponsive membrane. The thermoresponsive polymer, poly(N-isopropylacrylamide) (pNIPAM), is generated by the local reduction of persulfate ions, which initiates radical polymerization of NIPAM. Electrophoretic paint (EP) is chosen as an inert polymer. It is deposited by precipitation because of a local decrease in pH during water oxidation. Both polymers can be deposited simultaneously on opposite sides of the bipolar electrode during the application of the electric field, yielding a double-modified Janus object. Moreover, the length and thickness of the polymer layers can be controlled by varying the electric field and the deposition time. This concept is applied to vertically aligned carbon nanotube arrays (VACNTs), trapped inside an anodic aluminum oxide membrane, which can further be used as a smart reservoir for chemical storage and release. A fluorescent dye is loaded in the VACNTs and its release is studied as a function of temperature. Low temperature, when the hydrogel layer is in the swollen state, allows diffusion of the molecule. Dye release occurs on the hydrogel-modified side of the VACNTs. At high temperatures, when the hydrogel layer is in the collapsed state, dye release is blocked because of the impermeability of the pNIPAM layer. This concept paves the way toward the design of advanced devices in the fields of drug storage and directed delivery.

International audience; The rapid generation of material libraries with multidimensional gradients is important for the discovery of new functional materials. Here we report an integrated fabrication scheme, based on glancing angle physical vapor deposition, to form a thin-film materials library with controlled variations in nanoshape, multinary composition, and oxidation state on a single large area substrate. We demonstrate the versatility of the method by growing an octonary materials system, which we characterize with high-throughput methods, and reveal variations in several physico-chemical properties. Among others, we examine the materials library in the frame of the oxygen evolution reaction and show that nanostructuring leads to NiO clusters that are active towards such a reaction. Our scheme can be readily extended to include more starting elements, and can be transferred to other deposition methods, making this an adaptable and versatile platform for combinatorial materials science.

International audience; Electrochemical regeneration of reduced nicotinamide adenine dinucleotide (NADH) is an extremely important challenge for the electroenzymatic synthesis of many valuable chemicals. Although some important progress has been made with modified electrodes concerning the reduction of NAD+, the scale-up is difficult due to mass transport limitations inherent to large-size electrodes. Here, we propose instead to employ a dispersion of electrocatalytically active modified microparticles in the bulk of a bipolar electrochemical cell. In this way, redox reactions occur simultaneously on all of these individual microelectrodes without the need of a direct electrical connection. The concept is validated by using [Rh(Cp*)(bpy)Cl]+ functionalized surfaces, either of carbon felt as a reference material, or carbon microbeads acting as bipolar objects. In the latter case, enzymatically active 1,4-NADH is electroregenerated at the negatively polarized face of the particles. The efficiency of the system can be fine-tuned by controlling the electric field in the reaction compartment and the number of dispersed microelectrodes. This wireless bioelectrocatalytic approach opens up very interesting perspectives for electroenzymatic synthesis in the bulk phase.

International audience; Autonomous swimmers have been intensively studied in recent years due to their numerous potential applications in many areas, ranging from biomedicine to environmental remediation. Their motion is based either on different self-propulsion mechanisms or on the use of various external stimuli. Herein, the synergy between the ion flux around self-electrophoretic Mg/Pt Janus swimmers and an external magnetic field is proposed as an efficient alternative mechanism to power swimmers based on the resulting Lorentz force. A strong magnetohydrodynamic effect is observed due to the orthogonal combination of magnetic field and spontaneous ionic currents, leading reciprocally to an increase of the swimmer speed by up to two orders of magnitude. Furthermore, the trajectory of the self-propelled swimmers can be controlled by the orientation of the magnetic field, due to the presence of an additional torque force caused by a vertical cation flux along the swimmer edges, resulting in predictable clockwise or anticlockwise motion. In addition, this effect is independent of the swimmer size, since a similar type of chiral motion is observed for macro-and microscale objects.

This contribution reviews a selection of the most recent studies on the use of bipolar electrochemistry in the framework of analytical chemistry. Despite the fact that the concept is not new, with several important studies dating back to the middle of the last century, completely novel and very original approaches have emerged over the last decade. This current revival illustrates that scientists still (re)discover some exciting virtues of this approach, which are useful in many different areas, especially for tackling analytical challenges in an unconventional way. In several cases, this “wireless” electrochemistry strategy enables carrying out measurements that are simply not possible with classic electrochemical approaches. This review will hopefully stimulate new ideas and trigger scientists to integrate some aspects of bipolar electrochemistry in their work in order to drive the topic into yet unexplored and eventually completely unexpected directions.

International audience; Numerous artificial micro-and nanomotors, as well as various swimmers have been inspired by living organisms that are able to move in a coordinated manner. Their cooperation has also gained a lot of attention because the resulting clusters are able to adapt to changes in their environment and to perform complex tasks. However, mimicking such a collective behavior remains a challenge. In the present work, magnesium microparticles are used as chemotactic swimmers with pronounced collective features, allowing the gradual formation of macroscopic agglomerates. The formed clusters act like a single swimmer able to follow pH gradients. This dynamic behavior can be used to spot in a straightforward way localized corrosion events. The autonomous docking of the swimmers to the corrosion site leads to the formation of a local protection layer, thus increasing corrosion resistance and triggering partial self-healing.

The seasonal and longer-term dynamics of fuel accumulation affect fire seasonality and the occurrence of extreme wildfires. Failure to account for their influence may help to explain why state-of-the-art fire models do not simulate the length and timing of the fire season or interannual variability in burnt area well. We investigated the impact of accounting for different timescales of fuel production and accumulation on burnt area using a suite of random forest regression models that included the immediate impact of climate, vegetation, and human influences in a given month and tested the impact of various combinations of antecedent conditions in four productivity-related vegetation indices and in antecedent moisture conditions. Analyses were conducted for the period from 2010 to 2015 inclusive. Inclusion of antecedent vegetation conditions representing fuel build-up led to an improvement of the global, climatological out-of-sample R 2 from 0.579 to 0.701, but the inclusion of antecedent vegetation conditions on timescales ≥ 1 year had no impact on simulated burnt area. Current moisture levels were the dominant influence on fuel drying. Additionally, antecedent moisture levels were important for fuel build-up. The models also enabled the visualisation of interactions between variables, such as the importance of antecedent productivity coupled with instantaneous drying. The length of the period which needs to be considered varies across biomes; fuel-limited regions are sensitive to antecedent conditions that determine fuel build-up over longer time periods (∼ 4 months), while moisture-limited regions are more sensitive to current conditions that regulate fuel drying.