Interfacial Responses Research Articles

Coupling Vortical Bulk Flows to the Air–Water Interface: From Putting Oil on Troubled Waters to Surfactants on Protein Solutions

The air–water interface in flowing systems remains a challenge to model, even in cases where the interface is essentially flat. This is because even though each side is governed by the Navier–Stokes equations, the stress balance which provides the boundary conditions for the equations involves properties associated with surfactants that are inevitably present at the air–water interface. Aside from challenges in measuring interfacial properties, either intrinsic or flow-dependent, the two-way coupling of bulk and interfacial flows is non-trivial, even for very simple flow geometries. Here, we present an overview of the physics associated with surfactant monolayers of flowing liquid and describe how the monolayer affects the bulk flow and how the monolayer is transported and deformed by the bulk flow. The emphasis is primarily on cylindrical flow geometries, and both Newtonian and non-Newtonian interfacial responses are considered. We consider interfacial flows that are solenoidal as well as those where the surface velocity is not divergence free.

Comparison of binary cress seed mucilage (CSM)/β-lactoglobulin (BLG) and ternary CSG-BLG-Ca (calcium) complexes as emulsifiers: Interfacial behavior and freeze-thawing stability

Protein–polysaccharide complexes often exhibit amended techno-functional characteristics when compared to their individual participant biomolecules. In this study, a complex coacervation of cress seed mucilage (CSM)/β-lactoglobulin (Blg) was used for stabilizing oil-in-water emulsions; they were characterized in terms of physical properties, droplet-size distribution and microstructure. Also, a comprehensive study was carried out on interfacial rheological responses and on the corresponding emulsion stability of different complexes. Freeze-thaw stability of the produced emulsions which had from mixtures of CSM-Blg was also evaluated. More than the size of droplets, interfacial rheological characteristics were associated with the properties of the adsorbed layers and with the stability of emulsions in storage. Using the CSM-Blg-Ca ultimately resulted in emulsions that proved stable against creaming, with no sign of phase separation over 3 weeks. These results show protein–polysaccharide complexes as appropriate emulsifiers that can make emulsion-based products resistant to unwanted changes caused by freeze-thawing.

In situ demonstration of anodic interface degradation during water electrolysis: Corrosion and passivation

Understanding of interface-driven performance degradation in the oxygen evolution reaction (OER) is a prerequisite for developing long-term electrolytic systems operating at maximum efficiency. The question remains as to whether in situ observation of degradation during OER will be possible. We design a model system and fabricate a structure that is ideal for in situ detection of interfacial degradation that could occur at the anode, i.e. corrosion and passivation. The synthesized structure is based on carbon (C) or non-carbon (Ti); this is not only because it is a practical and general choice as an anode substrate, but also because it can represent the degradation reaction of corrosion or passivation, respectively. Interfacial responses from the ideally structured surface are observed (spectro)electrochemically under OER-operating conditions. We reveal that while electrochemical oxidation of C is inevitable over time, the passivation of Ti can be circumvented under controlled conditions. We also disclose that the use of Ti can be more beneficial for electrolytic cells, than that of C. These results highlight future research strategies required for the optimization of C- and Ti-based components used in electrolytic cells.

Pullout Behavior of Sensor-Enabled Geobelts in Weathered Rock Material–Granulated Rubber Mixtures

As lightweight materials, granulated rubber–weathered rock material (WRM) mixtures could be utilized as backfills in geosynthetics reinforcement structures to reduce deformations. However, the deformation behaviour of geosynthetics in granulated rubber–WRM mixtures is not clear. In this paper, pullout tests considering different normal pressures (30 kPa, 50 kPa and 100 kPa) and different granulated rubber contents (10%, 15% and 30%) are performed. Sensor-enable geobelts (SEGB) are employed, which can realize distributed measurements on the strains of SEGB inside soil. Two constitutive models—bilinear model and hyperbolic model are established based on tensile tests and direct shear tests to capture the full stress–strain curves and the interfacial shear responses, respectively, and are employed in the derivation of load transfer equation for pullout process. Numerical results of load transfer equation give distributions of tensile forces, strains, displacements and shear stresses. Test results validate the established constitutive models. Rubber content has an optimal value for the best geobelt–soil interaction. The deformations of geobelts in pullout process start from the front end, but decrease rapidly in soil. Under high normal pressures, the front part of geobelts exhibit quasi-plasticity. The shear stress distributes more uniformly under low normal pressure.

Interfacial and emulsion characterisation of chemically modified polysaccharides through a multiscale approach

HypothesisThe structural modification of natural emulsifiers may greatly impact their interfacial behaviours and bulk properties. The relationship between the microscopic interfacial viscoelasticity and the macroscopic emulsion stability in emulsifiers with different degrees of modification can be clarified using a multiscale approach. ExperimentsA polysaccharide emulsifier of corn fibre gum (CFG) with different octenyl succinate anhydride (OSA) contents was used to obtain a broad variety of interfacial properties. Interfacial adsorption kinetics and viscoelastic responses were measured by combining interfacial shear rheology and quartz crystal microbalance with dissipation monitoring, and the emulsion properties (droplet size and physical stability) at other scales were evaluated. FindingsCompared with native CFG, esterified CFG formed thick interfacial films with higher elasticity and viscosity, and their corresponding emulsions showed greater stability. There exists a satisfactory correlation between interfacial rheological properties and emulsion stability. However, such a satisfactory correlation can not be established among the degree of esterification of CFG, interfacial viscoelasticity and stability since depletion flocculation might occur in the emulsion stabilized by the OSA-CFG with the highest OSA content, which induced inferior bulk stability but exerted no impact on the measured interfacial properties. We propose that the depletion flocculation is responsible for this imperfection and provide detailed explanations.

Numerical verification of the Concentric Arches model for geosynthetic-reinforced pile-supported embankments: applicability and limitations

In this study, a series of three-dimensional finite element simulations of a geosynthetic-reinforced pile-supported embankment design was conducted. The effects of subsoil stiffness, friction and dilation angles of the fill, fill height, pile spacing, surcharge load on the embankment, and anisotropic tensile stiffness of the geosynthetic reinforcement (GR), ground reaction curve, and interfacial responses between the fill material and GR were scrutinized. Numerical results showed how transfer of the vertical load towards the piles (load part A) and the related soil arches change with subsoil stiffness, geometric parameters, and vertical pressure on the embankment. Furthermore, the vertical load transferred through the GR (load part B) is reduced significantly with increasing subsoil stiffness, while the load part carried by the subsoil (load part C) increases. The numerical results showed that the vertical stress distribution on the GR changes from an inverse-triangular shape for low subsoil stiffness to a uniform shape for high subsoil stiffness. This matches perfectly with the Concentric Arches model. For low subsoil stiffness, the tensile strains of the GR are concentrated at the corner of a square pile cap.

Finite element modelling of dynamic bonding behaviours between fibre reinforced polymer sheet and concrete

In this study, dynamic debonding behaviour between fibre-reinforced polymer (FRP) and concrete is numerically investigated by using finite element code LS-DYNA. A three-dimensional (3D) finite element (FE) model is built and a bond-slip model is incorporated into the simulation of interfacial bond between FRP and concrete. To validate the accuracy of the numerical model, experimental results from 42 dynamic single shear tests on FRP-concrete joints are employed. The debonding load and shear slip responses, FRP strain distributions, and interfacial bond-slip responses are compared between the numerical and experimental results. It is found that the numerical model is capable of predicting the debonding behaviours under various loading rates. In addition, an analytical dynamic bond strength model is proposed to predict the ultimate debonding strain and debonding load by incorporating the dynamic increase factor and strain rate. In addition, a semi-empirical model is proposed to predict the ultimate debonding strain and debonding load by incorporating the dynamic increase factor and strain rate. The semi-empirical model is validated against the numerical results and 119 experimental tests with a good correlation.

Influence of concrete strength on dynamic interfacial fracture behaviour between fibre reinforced polymer sheets and concrete

This study experimentally investigates the effect of concrete strength on the dynamic interfacial bond behaviour between basalt fibre reinforced polymer (BFRP) sheets and concrete under different loading speeds (i.e. 8.33E−6 m/s, 0.1 m/s, 1 m/s, 3 m/s, 5 m/s, and 8 m/s) by using single-lap shear tests. Three concrete strengths (i.e. C20, C30, and C40) were considered to examine the influence of concrete strength and strain rate on the interfacial bond-slip responses under dynamic loadings. The test results including the strain distributions, interfacial fracture energy, and bond-slip response were evaluated and discussed. The test results showed that the BFRP-concrete interface exhibited sensitivity to strain rate and the bond strength and shear resistance of the interface enhanced with strain rate. Compared with high strength concrete, low strength concrete showed higher strain rate sensitivity, which is induced by the different interfacial fracture mechanisms under different strain rates. An empirical bond-slip model incorporating strength effect of concrete and strain rate was proposed based on fracture mechanics.

CO2-responsive surfactants with tunable switching pH

HypothesisOne of the major challenges in applying CO2-responsive surfactants concerns their tunable switchability and robustness under operating conditions. We hypothesize that combining monoethanolamine (MEA) with long-chain fatty acids (LCFAs) of variable chain lengths through electrostatic attraction could develop a series of CO2-responsive surfactants with tunable switching pH. ExperimentsThe tunability of switching pH for this group of surfactants was demonstrated by in situ probing of the CO2-responsive characteristics at the oil/water interface using dynamic interfacial tension (IFT) measurements. Two protocols were applied to distinguish interfacial response and solution response. The key importance of interfacial response was demonstrated by two essential applications of CO2-responsive surfactants: demulsification of stable emulsions, and alternation of the interfacial properties of ultra-heavy crude oil-water interfaces. FindingsThe switching pH of the CO2-responsive surfactants was controlled by the hydrocarbon chain length of LCFAs. More importantly, their switching behaviour was found to be different at the interface and in the bulk solution, which is attributed to the enhanced molecular interactions at the interface. Since most applications require surfactants to be switched at the interface, it is thereby most appropriate to determine the switching pH through their interfacial responses.

Modification of the Electrochemical Behavior of InP Electrodes Induced By Ionic Bombardment: The Case of the Response of the Ce4+/Ce3+ Couple

The concept of modified electrode is very important for a lot of topics related to interfacial electrochemistry. It is particularly true when semiconductor (SC) interfacial electrochemistry is considered. Due to the specificities of the SC/liquid interfaces, modified SC electrodes have to be examined from different angles. The external part of the surface can be strongly modified due to the variations of surface /solution equilibrium inducing drastic transformations of the energy diagram at the interface. A direct consequence is a possible alteration of electronic transfers. Moreover the modification of the SC electrode can also concern deeper region through variation of the depletion layer distribution even of buried diffusion layer. Evolution of these parameters could again modify the energy diagram and the related electronic transfer abilities. Finally surface modifications can induced also evolution of the photoelectrochemical properties through evolution of the optical properties of the SC surface. All this different parameters are more or less related to the global response of the interface. It is in this context that our paper is being taken. For this study, our tool of surface modification is based on ion bombardment through mono-atomic or cluster Argon beams. Modulation of the perturbation induced by ion / SC surface interaction can be largely modulated by using mono or cluster Argon beam conditions [1]. In UHV the level and the nature of the perturbation can be easily in-situ evaluated from XPS responses evolutions from the core levels and also from the valence band. At this in-situ approach can be also associated optical responses such as ex-situ Ellipsometric Spectroscopy giving a global evaluation of the SC modification. As supporting SC material we choose InP whose surface, optical and interfacial electrochemical responses are well known in their initial stage before ionic bombardment. Based on well characterized InP (-n or -p) electrodes effect of ionic bombardment can be explored through a lot of electrochemical responses. Among the more attractive modification towards electronic transfer on InP, one can consider the addition in the electrolyte of a redox probe which acts as a perfect tool giving quantitative information for post bombardment. Ce4+/Ce3+ couple is particularly efficient due to its transfer specificities when its oxidant state (Ce4+) is only present [2-6]. Indeed pure holes injection inside the valance band (BV) is observed during the Ce4+ reduction mechanism which is only governed by the Ce4+ diffusion at the surface. As a direct consequence, the evolution of the reduction rate of Ce4+ can be easily measured vs the level of ionic bombardment. Moreover when InP is properly polarized all the holes injected are used in the anodic dissolution process with a very attractive and unusual conduction band (BC) injection phenomenon due to corrosion intermediates [6]. This is again a very sensitive probe to the level of modification of the InP surface after ionic bombardment. Note that this induced anodic process as a very similar potential distribution as the one obtained under illumination for which the holes creation is nevertheless only associated to the photon absorption. Common and difference points are also a subject of discussion for a characterization of the induced modifications. Finally we will discuss how an anodic and/or a chemical etching are able to regenerate the initial chemical state of the surface. The underlying question is how the anodic process linked to Ce4+/Ce3+ is sufficient to perform the surface regeneration even if it is initially modified by the ionic bombardment or if it requires the assistance of high positive polarization of the modified InP electrode.

In Situ Chemical Analysis of the Gas–Aerosol Particle Interface

The gas-aerosol particle interface is believed to contribute to the growth of secondary organic aerosols in the atmosphere. Despite its importance, the chemical composition of the interface has not been probed directly because of a lack of suitable interface-specific analytical techniques. The preliminary result in our early work has demonstrated direct observations of molecules at the gas-aerosol particle interface with the development of second harmonic scattering (SHS). However, the SHS technique is far away from being an analytical tool of chemical compositions at the gas-aerosol particle interface. In this work, we continued to develop the interface-specific SHS for in situ chemical analysis of molecules at the gas-aerosol particle interface. As an example, we demonstrated coherent SHS signal of a new SHS probe, crystal violet (CV), from interfaces of aerosol particles. The development of the SHS technique includes: (1) Optimization for a more efficient femtosecond laser system in the generation of SHS from aerosol particles. A near 5 MHz repetition rate of a femtosecond laser was found to be optimal for the generation of SHS; (2) exploration of a more effective detector for SHS of aerosol particles. We found that both a CCD detector and a single-photon counter produce similar signal-to-noise ratios of the interfacial SHS signals from aerosol particles. The CCD detector is a more effective option for the detection of SHS and could greatly reduce sampling time of the interfacial responses; (3) combination of the optimal laser system with the CCD detector, which has greatly improved the detection sensitivity of interfacial molecules by more than 2 orders of magnitude and could potentially detect interfacial SHS from a single aerosol particle. These experimental results not only provided a thorough analysis of the SHS technique but also built a solid foundation for further development of a new vibrational sum frequency scattering (SFS) technique for chemical structures at the gas-aerosol particle interface.

Interfacial behavior and debonding failures of full-scale CFRP-strengthened H-section steel beams

Strengthening existing steel beams with externally bonded carbon fiber-reinforced polymer (CFRP) plate has attracted many interests in the research community. Debonding of the CFRP plate is the dominant failure mode in a flexurally strengthened steel beam, and the debonding failure is controlled by the interfacial responses between the CFRP plate and the substrate steel beam. Although some experimental investigations have been conducted on CFRP-strengthened steel beams, limited test results on the interfacial stress and strain responses especially in full-scale steel beams, are available to verify the numerical modeling. This paper presents an experimental study on the flexural behavior of full-scale CFRP-strengthened H-section steel beams. The effects of different bond lengths of CFRP plates and the presence of steel stiffeners are investigated. The test results in terms of the failure modes, load-deflection responses, CFRP strains, interfacial shear stress distributions are reported in detail. A three-dimensional finite element model is proposed to predict the flexural performance of full-scale CFRP-strengthened steel beams, and it is then validated extensively by the test results.

Strength distribution of Ti/SiC metal-matrix composites under monotonic loading

The strength of metal matrix composites shows wide scatter on account of variability in the strengths of individual fibres. The relationship between the strength distribution of the fibres, and that of the composite is also affected by the non-linear matrix and fibre/matrix interfacial responses. The present study aims to describe the strength distribution of 2D and 3D commercial Ti/SiC composites. This is accomplished by performing Monte Carlo failure simulations of these composites, comprised of up to 128 fibres. A detailed deformation theory based model, developed and validated against experimental data in previous work, is used to calculate load redistribution in the course of each simulation. The empirical composite strength distribution obtained from the simulations follows weakest-link scaling. A stochastic model for the clustered propagation of fibre breaks, akin to a model proposed for polymer matrix composites in the literature, captures the empirical weakest-link strength distribution. A scaling relationship is derived between the composite strength and composite size for a number of reliability levels.

Prediction of shock initiation thresholds and ignition probability of polymer-bonded explosives using mesoscale simulations

The design of new materials requires establishment of macroscopic measures of material performance as functions of microstructure. Traditionally, this process has been an empirical endeavor. An approach to computationally predict the probabilistic ignition thresholds of polymer-bonded explosives (PBXs) using mesoscale simulations is developed. The simulations explicitly account for microstructure, constituent properties, and interfacial responses and capture processes responsible for the development of hotspots and damage. The specific mechanisms tracked include viscoelasticity, viscoplasticity, fracture, post-fracture contact, frictional heating, and heat conduction. The probabilistic analysis uses sets of statistically similar microstructure samples to directly mimic relevant experiments for quantification of statistical variations of material behavior due to inherent material heterogeneities. The particular thresholds and ignition probabilities predicted are expressed in James type and Walker–Wasley type relations, leading to the establishment of explicit analytical expressions for the ignition probability as function of loading. Specifically, the ignition thresholds corresponding to any given level of ignition probability and ignition probability maps are predicted for PBX 9404 for the loading regime of Up = 200–1200 m/s where Up is the particle speed. The predicted results are in good agreement with available experimental measurements. A parametric study also shows that binder properties can significantly affect the macroscopic ignition behavior of PBXs. The capability to computationally predict the macroscopic engineering material response relations out of material microstructures and basic constituent and interfacial properties lends itself to the design of new materials as well as the analysis of existing materials.

Measuring Interlayer Shear Stress in Bilayer Graphene.

Monolayer two-dimensional (2D) crystals exhibit a host of intriguing properties, but the most exciting applications may come from stacking them into multilayer structures. Interlayer and interfacial shear interactions could play a crucial role in the performance and reliability of these applications, but little is known about the key parameters controlling shear deformation across the layers and interfaces between 2D materials. Herein, we report the first measurement of the interlayer shear stress of bilayer graphene based on pressurized microscale bubble loading devices. We demonstrate continuous growth of an interlayer shear zone outside the bubble edge and extract an interlayer shear stress of 40kPa based on a membrane analysis for bilayer graphene bubbles. Meanwhile, a much higher interfacial shear stress of 1.64MPa was determined for monolayer graphene on a silicon oxide substrate. Our results not only provide insights into the interfacial shear responses of the thinnest structures possible, but also establish an experimental method for characterizing the fundamental interlayer shear properties of the emerging 2D materials for potential applications in multilayer systems.

Dynamic properties of Span-80 adsorbed layers at paraffin-oil/water interface: Capillary pressure experiments under low gravity conditions

Measurements by capillary pressure tensiometry, under microgravity conditions aboard the International Space Station, supplied a consistent set of reliable results for the dynamic interfacial tension and for the interfacial dilational viscoelastic modulus, quantitatively characterizing the dynamics of Span-80 adsorbed layers at the paraffin-oil/water interface.The experiments were executed at three different temperatures, i.e., 20, 30 and 40°C, according to a pre-established built-in time-line in the orbiting facility. The interfacial area was subjected to perturbations with various functional forms (square pulses, ramps and harmonic oscillations), at three consecutive amplitudes (5%, 10% and 20%). Each experiment was performed in three successive repetitions, in view of an advantageous telemetered data redundancy.The interfacial responses to imposed perturbations, for the studied minimal surfactant concentration of Span-80 in paraffin-oil (that is (2÷3)×10−5mol/dm3) revealed a diffusion-controlled adsorption mechanism, definitely matching the Lucassen & Van den Tempel model in the frequency-domain representation. The interfacial responses also showed a linearity range up to the 20% amplitude.Interfacial relaxation responses to transient interfacial perturbations substantially validated the diffusion-controlled model for the adsorption mechanism, in the time-domain representation.

Comparative viscoelasticity studies: Corn fiber gum versus commercial polysaccharide emulsifiers in bulk and at air/liquid interfaces

A comparative study of both the bulk and air/liquid interfacial rheological responses was carried out by using four kinds of representative high molecular weight and highly branched polysaccharide emulsifiers, (a) corn fiber gum (CFG), (b) octenyl succinate anhydride-modified starch (OSA-s), (c) gum arabic (GA) and (d) soybean soluble polysaccharides (SSPS), spanning the concentration range of 1–15 wt%. We found that the bulk and interfacial rheological properties of their aqueous solutions were significantly different. While both CFG and OSA-s showed Newtonian flow behavior at higher concentrations, both GA and SSPS exhibited obviously shear thinning behavior or thixotropy even at a low concentration of 1 wt%. The time-dependent flow behavior for CFG, GA and SSPS reflected microstructural breakdown and rebuilding in solutions under shear, indicated that their proteinaceous portion was strongly bound to their polysaccharide part. This phenomenon was not observed for the almost protein-free OSA-s. The interfacial rheology responses showed that the layers formed by CFG and OSA-s were viscously predominant with faster formation kinetics while they were elastically predominant for GA and SSPS with slower formation kinetics. Interfacial viscoelastic responses of CFG and OSA-s were weaker than those of GA and SSPS. By comparison, the interfacial layer for OSA-s showed pure viscous responses whereas SSPS showed the highest elastic responses. These significant disparities in bulk and interfacial viscoelasticity of the four polysaccharide emulsifiers reflect the influence of different fine chain structures on the dissimilarity in the intermolecular associations and the architectures of the interfacial layers.

Measurements of Submicron Particle Adsorption and Particle Film Elasticity at Oil-Water Interfaces.

The influence of particle adsorption on liquid/liquid interfacial tension is not well understood, and much previous research has suggested conflicting behaviors. In this paper we investigate the surface activity and adsorption kinetics of charge stabilized and pH-responsive polymer stabilized colloids at oil/water interfaces using two tensiometry techniques: (i) pendant drop and (ii) microtensiometer. We found, using both techniques, that charge stabilized particles had little or no influence on the (dynamic) interfacial tension, although dense silica particles affected the "apparent" measured tension in the pendent drop, due to gravity driven elongation of the droplet profile. Nevertheless, this apparent change additionally allowed the study of adsorption kinetics, which was related qualitatively between particle systems by estimated diffusion coefficients. Significant and real interfacial tension responses were measured using ∼53 nm core-shell latex particles with a pH-responsive polymer stabilizer of poly(methyl methacrylate)-b-poly(2-(dimethylamino)ethyl methacrylate) (pMMA-b-pDMAEMA) diblock copolymer. At pH 2, where the polymer is strongly charged, behavior was similar to that of the bare charge-stabilized particles, showing little change in the interfacial tension. At pH 10, where the polymer is discharged and poorly soluble in water, a significant decrease in the measured interfacial tension commensurate with strong adsorption at the oil-water interface was seen, which was similar in magnitude to the surface activity of the free polymer. These results were both confirmed through droplet profile and microtensiometry experiments. Dilational elasticity measurements were also performed by oscillation of the droplet; again, changes in interfacial tension with droplet oscillation were only seen with the responsive particles at pH 10. Frequency sweeps were performed to ascertain the dilational elasticity modulus, with measured values being significantly higher than previously reported for nanoparticle and surfactant systems, and similar in magnitude to protein stabilized droplets.

Effects of Hollow Fly-Ash Particles on the Properties of Magnesium Matrix Syntactic Foams: A Review

Abstract In the past decade, magnesium has been seen as one of the most potential metals for weight-critical engineering applications. As magnesium is the lightest structural metal, it has higher weight-saving capabilities when compared to aluminum. Significant research efforts have been carried out on magnesium matrix alloys and composites to tailor and enhance mechanical properties based on end applications. This paper provides a review on fly-ash-reinforced magnesium matrix syntactic foams. Fly-ash cenospheres are made up of mainly alumina and silica and also contains large number of trace elements, which makes it intriguing to analyze the microstructure and interfacial responses of the end composites. In comparison with aluminum matrix syntactic foams, the research on magnesium matrix syntactic foams is still at an incipient stage. This paper provides an insight on processing techniques, microstructural and mechanical evaluations of pure Mg, AZ, and ZC alloy series, and their syntactic foams. This paper also reviews the weight-saving ability of magnesium matrix syntactic foams and their potential scope and applications.

High throughput second harmonic imaging for label-free biological applications.

Second harmonic generation (SHG) is inherently sensitive to the absence of spatial centrosymmetry, which can render it intrinsically sensitive to interfacial processes, chemical changes and electrochemical responses. Here, we seek to improve the imaging throughput of SHG microscopy by using a wide-field imaging scheme in combination with a medium-range repetition rate amplified near infrared femtosecond laser source and gated detection. The imaging throughput of this configuration is tested by measuring the optical image contrast for different image acquisition times of BaTiO₃ nanoparticles in two different wide-field setups and one commercial point-scanning configuration. We find that the second harmonic imaging throughput is improved by 2-3 orders of magnitude compared to point-scan imaging. Capitalizing on this result, we perform low fluence imaging of (parts of) living mammalian neurons in culture.