Final Droplet Size Research Articles

Production of Monodisperse Large Drop Emulsions by Means of High Internal Phase Pickering Emulsions-Processing and Formulation.

High internal phase Pickering emulsions (HIPPE) have received significant research attention in the last two decades due to their potential for a wide range of applications. The appropriate processing of such high-viscosity emulsions, hundreds of times more viscous than that of the continuous phase, and the control of the final droplet size remain challenges to be tackled. Our research targeted this knowledge gap by examining the influence of the emulsion formulation and the processing conditions on the final droplet size. The dispersed phase fraction (100 cSt silicon oil) ranged between 75 and 80%. The emulsions were produced in a regular mixing tank equipped with a helical ribbon impeller rotating at a low speed (100-150 rpm). The effective viscosity of the continuous phase was obtained from the experimental torque measurements. The droplet size distributions were measured after emulsification and dilution in the continuous phases. It is shown that the capillary number obtained from the observed emulsification performance can help predict the final droplet size. Our approach provides a straightforward methodology to generate concentrated Pickering emulsions with controlled and predictable droplet size.

Using Computation Fluid Dynamics to Determine Oil Droplet Breakup Parameters during Emulsion Atomization with Pressure Swirl Nozzles

A wide range of commercial powdered products are manufactured by spray drying emulsions. Some product properties are dependent on the oil droplet size, which can be affected by fluid mechanics inside the spray nozzle. However, most of the key flow parameters inside the nozzles are difficult to measure experimentally, and theoretical estimations present deviations at high shear rates and viscosities. Therefore, the purpose of this study was to develop a computational model that could represent the multiphase flow in pressure swirl nozzles and could determine the deformation stresses and residence times that oil droplets experience. The multiphase flow was modelled using the Volume-of-Fluid method under a laminar regime. The model was validated with experimental data using the operating conditions and the spray angle. The numerically calculated shear stresses were found to provide a better prediction of the final oil droplet size than previous theoretical estimations. A two-step breakup mechanism inside of the nozzle was also proposed. Additionally, some of the assumptions used in the theoretical estimations could not be confirmed for the nozzles investigated: No complete air core developed inside of the nozzle during atomization, and the shear stress at the nozzle outlet is not the only stress that can affect oil droplet size. Elongation stresses cannot be neglected in all cases.

Effect of Flow Rate Modulation on Alginate Emulsification in Multistage Microfluidics.

The encapsulation of stem cells into alginate microspheres is an important aspect of tissue engineering or bioprinting which ensures cell growth and development. We previously demonstrated the encapsulation of stem cells using the hanging drop method. However, this conventional process takes a relatively long time and only produces a small-volume droplet. Here, an experimental approach for alginate emulsification in multistage microfluidics is reported. By using the microfluidic method, the emulsification of alginate in oil can be manipulated by tuning the flow rate for both phases. Two-step droplet emulsification is conducted in a series of polycarbonate and polydimethylsiloxane microfluidic chips. Multistage emulsification of alginate for stem cell encapsulation has been successfully reported in this study under certain flow rates. Fundamental non-dimensional numbers such as Reynolds and capillary are used to evaluate the effect of flow rate on the emulsification process. Reynolds numbers of around 0.5-2.5 for alginate/water and 0.05-0.2 for oil phases were generated in the current study. The capillary number had a maximum value of 0.018 to ensure the formation of plug flow. By using the multistage emulsification system, the flow rates of each process can be tuned independently, offering a wider range of droplet sizes that can be produced. A final droplet size of 500-1000 µm can be produced using flow rates of 0.1-0.5 mL/h and 0.7-2.4 mL/h for the first stage and second stage, respectively.

Condensation particle counters: Exploring the limits of miniaturisation

The measurement of airborne particles continues to attract increased interest for the detection and characterisation of air pollution, emissions, fire detection, occupational and climate impacts. Concerted efforts have reduced the size and cost of optical counters that have enabled widespread sensor deployment. Currently the World Health Organisation (WHO) enforces particle regulations that are mass-based which has resulted in an influx of low-cost portable optical particle counters (OPCs) calibrated to mass standards and widely utilised for research and personal monitoring. However, OPCs are incapable of measuring particles with diameters dp≲ 300 nm which misses ultrafine particles (≤ 100 nm) that often represent the majority of particles by number concentration. Condensation particle counters (CPCs) capable of measuring ultrafine particle number concentration with high instrument sensitivity, accuracy and precision have recently been targeted for miniaturisation.Herein, we explore the limitations of the miniaturisation of a CPC growth chamber (CPC-GC). Results presented in this work use water, but equivalent expressions can be obtained for other working fluids or design criteria using the same methods. Scaling analysis considers phenomenological constraints of supersaturation, heat transfer, particle penetration and droplet growth to establish limits during miniaturisation.The results showed that optimal thermal and saturation conditions are similar where the optimum device aspect ratio is L∗≥Lmin,s∗= 1.68 Re + 7.98 and L∗≥Lmin,th∗= 1.78 Re + 8.02 respectively. L∗ is the non-dimensional aspect ratio and Lmin∗ is the minimum non-dimensional device length required as a function of the flow Reynolds number Re. Higher Reynolds numbers lead to a convection-dominated regime, where the saturation and temperature profiles take a parabolic shape. As the Reynolds number approaches unity, the reduced mass and thermal Péclet numbers result in vapour and heat diffusing upstream of the condenser, creating ellipsoidal saturation and temperature profiles. To achieve a satisfactory performance, the heat and mass transport within the CPC-GC must be convection-dominated, leading to a minimum value of Re ≳2. Desired penetration P≥0.9 for particles with an initial diameter dpinit=10nm is achieved by designs with an aspect ratio, L∗≤Lmax,p∗= 2.5 Re. Together, these constraints define an allowable range of aspect ratios for a CPC-GC as a function of the Reynolds number.The final size of the grown droplets can be controlled by varying the interaction residence time τint, defined as the time a particle spends in the supersaturation profile. Having defined a target final droplet size for optical detection, and hence having fixed τint, the aspect ratio necessary to achieve the desired growth is a function of the Reynolds number and of the dimensional radius of the CPC-GC (Ricpc) according to: Lgrowth∗=γRe/(Ricpc)2 with γ= 2τintν, where ν is the kinematic viscosity of air. Selecting a value of Ricpc such that the line for Lgrowth∗ falls in the centre of the allowable operating region defined above will optimise the dimensional CPC-GC for the selected design criteria.Limits from this model were used to realising a prototype successfully tested experimentally against a reference commercial CPC within a laboratory environment. The outcome of the present work enables designers and researchers with a toolkit to optimise the next generation of high performance miniaturised CPC-GC designs.

Surfactant-laden droplet size prediction in a flow-focusing microchannel: a data-driven approach.

The control of droplet formation and size using microfluidic devices is a critical operation for both laboratory and industrial applications, e.g. in micro-dosage. Surfactants can be added to improve the stability and control the size of the droplets by modifying their interfacial properties. In this study, a large-scale data set of droplet size was obtained from high-speed imaging experiments conducted on a flow-focusing microchannel where aqueous surfactant-laden droplets were generated in silicone oil. Three types of surfactants were used including anionic, cationic and non-ionic at concentrations below and above the critical micelle concentration (CMC). To predict the final droplet size as a function of flow rates, surfactant type and concentration of surfactant, two data-driven models were built. Using a Bayesian regularised artificial neural network and XGBoost, these models were initially based on four inputs (flow rates of the two phases, interfacial tension at equilibrium and the normalised surfactant concentration). The mean absolute percentage errors (MAPE) show that data-driven models are more accurate (MAPE = 3.9%) compared to semi-empirical models (MAPE = 11.4%). To overcome experimental difficulties in acquiring accurate interfacial tension values under some conditions, both models were also trained with reduced inputs by removing the interfacial tension. The results show again a very good prediction of the droplet diameter. Finally, over 10 000 synthetic data were generated, based on the initial data set, with a Variational Autoencoder (VAE). The high-fidelity of the extended synthetic data set highlights that this method can be a quick and low-cost alternative to study microdroplet formation in future lab on a chip applications, where experimental data may not be readily available.

Polyphenol Loaded W1/O/W2 Emulsions Stabilized with Lesser Mealworm (Alphitobius diaperinus) Protein Concentrate Produced by Membrane Emulsification: Stability under Simulated Storage, Process, and Digestion Conditions.

Water-in-oil-in-water (W1/O/W2) emulsions are complex delivery systems for polyphenols amongst other bio-actives. To stabilize the oil–water interphase, dairy proteins are commonly employed, which are ideally replaced by other, more sustainable sources, such as insect proteins. In this study, lesser mealworm (Alphitobius diaperinus) protein concentrate (LMPC) is assessed and compared to whey protein (WPI) and pea protein (PPI), to stabilize W1/O/W2 emulsions and encapsulate a commercial polyphenol. The results show that LMPC is able to stabilize W1/O/W2 emulsions comparably to whey protein and pea protein when using a low-energy membrane emulsification system. The final droplet size (d4,3) is 7.4 μm and encapsulation efficiency is between 72 and 74%, regardless of the protein used. Under acidic conditions, the LMPC shows a similar performance to whey protein and outperforms pea protein. Under alkaline conditions, the three proteins perform similarly, while the LMPC-stabilized emulsions are less able to withstand osmotic pressure differences. The LMPC stabilized emulsions are also more prone to droplet coalescence after a freeze–thaw cycle than the WPI-stabilized ones, but they are the most stable when exposed to the highest temperatures tested (90 °C). The results show LMPC’s ability to stabilize multiple emulsions and encapsulate a polyphenol, which opens the door for application in foods.

Enhancing long-term accuracy and durability of wastewater monitoring using electrosprayed ultra-thin solid-state ion selective membrane sensors

Current membrane deposition approaches (e.g., drop-casting, spin-coating) for solid-state ion selective membrane (S-ISM) sensors suffer from problems including sensor material waste, uncontrollable membrane thickness (100–200 μm), loose contact between sensing membrane and electrode surface, long response time (e.g., >20 s) and poor reading stability (e.g., >3 mV/h). This study addressed these challenges by depositing ISM through electrospray printing technology and enabling accurate and continuous monitoring in water and wastewater. Specifically, the final droplet size and the splash diameter of the electrosprayed droplets deposited a particularly tunable, high resolution and ultra-thin (thickness: ∼1 μm) membrane on the electrode surface, which immensely shortened the sensor response time (9.2 s), strengthened the adhesion between the ISM and the electrode surface, mitigated the formation of water layer in the S-ISM sensor entity, and ultimately enhanced the sensor reading stability (reading drifting <0.66 mV/h). Additionally, the ion diffusion model developed in this study confirmed that fast ion diffusion in the electrosprayed S-ISM polymer matrix effectively shortened the response time of sensors. Electrosprayed S-ISM sensors without anti-fouling protection exhibited high stability and accuracy with an error of less than 2.9 mg/L after continuously monitoring wastewater for 10 days, revealing a great potential for further enhancement.

Large eddy simulation and experiment of shear breakup in liquid-liquid jet: Formation of ligaments and droplets

Understanding the shear breakup in jet flows and the formation of droplets from ligaments is important to determine the final droplet size distribution (DSD). The initial droplet size, which affects the final DSD, is considered to be generated by the shear breakup. Large eddy simulation (LES) was performed to investigate the shear breakup in liquid-liquid jet flows. The explicit Volume of Fluid (VOF) model with the geometric reconstruction scheme was used to capture the oil-water interface. The estimated oil distribution including wave peaks, ligaments, droplets and water streaks were compared to the experiments with a good agreement. The estimated DSD matched with the measurements favorably well. In the simulation, the formation of droplets with a smooth and curved surface from ligaments or sheet-like structures was obtained. Different mechanisms were observed along with the shear layer including the formation of droplets from ligament through the capillary forces, breakage of a droplet into smaller ones and attachment of a droplet to a ligament. The destructive shear forces and resisting surface tension forces were quantified on stretching and retracting ligaments. The influence of internal viscous force was found to be negligible due to low oil viscosity. The critical capillary number was found to be larger than 5.0 for ligaments breaking with the shear breakup. The capillary number was below unity for retracting ligaments. The coalescence of two equal-sized droplets was obtained in the shear breakup region. The shear stress magnitude at the contact region increased more than two folds. The total surface area decreased nearly 20% after the coalescence.

Micro‐computed tomography for the 3D time‐resolved investigation of monodisperse droplet generation in a co‐flow setup

AbstractDroplet generation in microfluidic devices has emerged as a promising approach for the design of highly controllable processes in the chemical and pharmaceutical industry. However, droplet generation is still not fully understood due to the complexity of the underlying physics. In this work, micro‐computed tomography is applied to investigate droplet formation in a circular channel in a co‐flow configuration at different flow conditions (Ca &lt; 0.001). The application of an in‐house developed scanning protocol assisted by comprehensive image processing allows for the time‐resolved investigation of droplet formation. By tracking different droplet parameters (length, radii, volume, surface, Laplace pressure) the effect of flow conditions on droplet progression is determined. As characteristic for the squeezing regime, final droplet size was nearly independent of Ca for higher Ca tested. For lower Ca, the final droplet size increased with decreasing Ca, which points to the leaking regime that was recently introduced in the literature.

Resveratrol loaded Pickering emulsions stabilized by OSA modified rice starch granules

Resveratrol is a photosensitive, bioactive molecule which has received increasing research interest during the past decade for its antioxidant properties. However, it has low solubility in water or common triglyceride oils. Resveratrol solubilization in oil can only be achieved in essential oils, such as flavour oils, but the stability of emulsions produced with this type of oils is low as they are prone to creaming phenomena and Oswald ripening.In this study, resveratrol was first dissolved in orange oil which was mixed into a medium-chain triglyceride (Miglyol) at different ratios and used as the internal phase of oil-in-water emulsions (O/W). The emulsions were stabilized by octenyl succinic anhydride (OSA) modified rice starch granules using two different ratios of starch particle:oil to study the influence of interfacial coverage on the final emulsion droplet size and emulsion stability.The results of this study indicated that stable Pickering emulsions could be prepared using OSA-modified rice starch granules even at partial coverage conditions. Emulsions prepared at an oil fraction of 0.5 using 30% v/v mixture of orange oil in Miglyol as the dispersed phase seemed to be an appropriate resveratrol carrier system, obtaining encapsulation efficiency values close to 90% which results in emulsions with a resveratrol concentration of 8.45 mg/L. Hence, the emulsions prepared are suitable for food fortification applications.

Effects of a Coflowing Air on the Characteristics of an Electrospray

An electrospray with a coflowing nebulizing air is characterized for three different electrospray modes: spindle, cone jet, and unstable. An electrospray with dimensions used in a mass spectrometer with 150-μm ID nozzle was characterized. The droplet size and velocity distributions were measured using a Phase Doppler Particle Analysis (PDPA) with and without the coflowing air. The significance of the coflowing air on the final spray droplet size and velocity distribution is found to depend on the electrospray mode. Generally, the coflowing air increases both the droplet size and velocity distributions, and the increase is more significant in the spindle mode than the cone jet mode.

Fragmentation versus Cohesion

Capillarity is the familiar manifestation of the cohesion of liquids. Since Laplace (Traite de mecanique celeste, vol. IV, supplement au livre X: Sur l’action capillaire, 1805, pp. 1–65), we know that intense attractive forces between the molecules bridge the small with the large as they shape liquid/vapour interfaces at the macroscopic scale through the concept of surface tension (menisci, drops, bubbles, puddles, liquid rise in tubes, etc. …). We concentrate on situations where liquids ‘disgregate’, following the neologism of Clausius (Phil. Mag., vol. 24 (159), 1862, pp. 81–97), meaning that they fragment by the action of deformation stresses whose intensity competes with that of cohesion forces. Various examples, including explosions, blow-ups, hard and soft impacts and shears applied to liquid jets, sheets and drops are reviewed. They concern applications ranging from liquid propulsion, agricultural spraying, to the formation of ocean spray, raindrops and human exhalations by violent respiratory events. In spite of their diversity, the various modes of fragment production share an ultimate common phenomenology – the ligament dynamics – suggesting that the final stable droplet size distribution can be interpreted from elementary principles.

Formation of drug-loaded nanoemulsions in stirred media mills

The feasibility of stirred media mills for the production of nanoemulsions loaded with active pharmaceutical ingredients (API) using plant oils as disperse phase and different types of the non-ionic emulsifier polysorbate is demonstrated. The influence of the emulsion formulation, namely oil type, surfactant and surfactant-to-oil-weight-ratio (SOR) on the product droplet size at constant stressing conditions is studied in detail. At similar stressing conditions and SOR, the type of the used plant oil and surfactant did not influence the product droplet size and the smallest achievable median droplet size was 20 nm. The API saturated oil phases and the pure oil phases exhibit similar viscosities, emulsification kinetics and final product droplet sizes, i.e. no influence of the API on the emulsification process could be identified. However, a strong dependency of the emulsion droplet size on the SOR has been observed. Moreover, very good long-term stabilities could be achieved for the obtained emulsions. A release test with fenofibrate-loaded peanut oil-polysorbate 80-water nanoemulsions showed remarkably fast drug distribution as compared to a formulation containing the same amount of the non-dissolved micronized drug.

Effect of injector swirl number on near-field spray characteristics of a novel twin-fluid injector

Compared to liquid jets/films from conventional air-blast injectors, flow blurring (FB) injection has generated fine sprays immediately at the injector exit, resulting in the clean combustion of various fuels including viscous oils. The FB atomization involves primary atomization by bubble bursting of the bubbly internal two-phase flow due to the dramatic pressure drop at the injector exit and the secondary break-up of droplets/ligaments by Rayleigh–Taylor instability. Recently, a novel swirl-burst (SB) injector has been developed to further enhance the secondary atomization, which has resulted in less lifted and cleaner flames by integrating swirling atomizing air with the FB concept. The present study investigates the effect of injector swirl number (ISN) on spray characteristics including droplet velocity and size distributions in the injector near field (8 mm × 4 mm) using particle image velocimetry and shadowgraph imaging for the SB injectors with diameter, D, of 1.5 mm. The study investigates four ISNs from 2.0 to 3.5 with an increment of 0.5, corresponding to various swirl vane angles. Results show that all the ISNs have achieved a short break-up length (~ 1.67D) and fine atomization with final droplet diameter ranging from 12 to 40 µm and SMD around 25 µm. Droplets are evenly distributed at each axial plane for all the ISNs. Increase in the ISN results in enhanced secondary atomization and hence finer droplets within 1.67D downstream of the injector exit. Spray angles are typically narrower at the increased ISN. Regardless of the variations within the injector near field and the different spray angles, the break-up length and final droplet size are nearly independent of the ISN.

Numerical study of droplet formation in the T-junction microchannel with wall velocity slip

Effect of hydrophobicity on droplet formation in the T-junction microfluidic devices is numerically studied. A Navier slip model is adopted. Results reveal that, as increasing of slip length, the velocity profile across the channel becomes flattened. With the increase of slip length, the shear stress on dispersed phase exerted by the continuous phase decreases, thus, the deformation of the dispersed phase weakens while the final droplet size increases. The pressure distributions along the central axis of main channel show a smaller pressure drop when the wall velocity slip length increases.

DETAILED NUMERICAL SIMULATIONS OF ATOMIZATION OF A LIQUID JET IN A SWIRLING GAS CROSSFLOW

Breakup of a liquid jet in a high speed gaseous crossflow finds wide range of engineering and technological applications, especially in the combustors of the gas turbine engines in aerospace industry. In this study, we present volume-of-fluid method based direct numerical simulations of a liquid jet injected into a swirling crossflow of gas. The liquid is injected radially outwards from a central tube to a confined annular space with a swirling gas crossflow. The essential features of the jet breakup involving jet flattening, surface waves and stripping of droplets from the edges of the jet are captured in the simulations. We discuss the effect of swirl on the spray characteristics such as jet trajectory, column breakup-length, and size, shape-factor and velocity distribution of the drops. Drop size increases with swirl and penetration is slightly reduced. Moreover, the trajectory follows an angle (azimuthal) that is smaller than the geometric angle of the swirl at the inlet. Interestingly, we also observe coalescence events downstream of the jet that affect the final droplet size distribution for the geometry considered in this study.

Investigation of water spray characteristics in the near field of a novel swirl burst injector

The limit of fossil fuels and more stringent emission standards have prompted the exploration of renewable biofuels and clean combustion technology. Clean and efficient combustion of liquid fuels mainly relies on spray fineness achieved by fuel injectors. Conventional injectors such as the air blast (AB) nozzles are only effective for low-viscosity fuels. Hence, viscous source oils of biofuels have to be converted into “drop-in” fuel such as biodiesel, leading to the high production cost of biofuels. In the past decade, the flow blurring (FB) injection using a two-phase flow concept has proved to generate fine sprays for even highly viscous liquids in the near field of injector exit, rather than a typical fuel jet from AB injectors. Thus, the FB injection has achieved cleaner burning of fossil fuels and enabled clean lean-premixed combustion of viscous oils including biodiesel source oils, signifying cost-effective biofuel utilization without the conversion cost. Recently, our group designed a novel twin-fluid swirl burst (SB) injector that integrates the advantages of FB and further improves secondary atomization caused by Rayleigh-Taylor instabilities. The SB design innovatively introduces swirling atomizing air (AA) to stimulate more vigorous interaction between AA and large droplets or ligaments from the primary FB atomization by bubble-bursting. The present study compares the water spray micro-characteristics of FB and SB injectors in the near field of the injector exit at the same flow conditions using high spatial resolution particle image velocimetry and shadowgraph imaging systems. Results show that, compared to the FB atomization, the novel SB injector has successfully generated a wider spray with finer droplets immediately at the exit orifice and a shorter atomization completion length, indicating the improved secondary atomization. Estimate of Weber number and Ohnesorge number consistently substantiates the improved SB atomization and suggests bag breakup dominating the secondary atomization for both injectors. Radial profiles of Sauter Mean Diameter indicate the SB injection yields uniform droplet size distribution compared to the FB injection that has relatively larger droplets mainly at the spray periphery. Regardless of the variations in the atomizer near region, both SB and FB injector generate fine sprays with similar final droplet size.

An analytical model of final average droplet size prediction of wave spray cloud

This study introduces an analytical model to predict the final average droplet size within a spray cloud that is formed due to wave interactions with marine objects. The process of spray cloud formation from wave impact involves several complicated processes, and each of these phenomena should be taken into account when considering an analytical approach. Following this process-based approach, the model first considers the wave characteristics and relates wave properties to the maximum impact pressure also considering the effect of air entrapment occurrence. Secondly, the maximum impact pressure is correlated empirically to the maximum wave run-up velocity. Finally, wave run-up velocity is linked with water sheet breakup models, which leads to the prediction of the final average diameter of ligaments and droplets. The prediction model is compared with experimental measurements from experiments conducted in a tow tank to form a spray cloud due to wave impact with two lab-scale models. Several measuring techniques such as image processing, bubble image velocimetry (BIV), and digital particle image velocimetry (DPIV) methods were implemented to measure the physical quantity of each phenomenon during the event of wave interaction. The effects of initial wave characteristics, the geometrical parameters of the impact condition and water sheet thickness at the moment of impact, on the final average droplet diameter were investigated. A sensitivity analysis of most of the principal parameters was performed to show the high veracity of the prediction model.

O/W Pickering emulsions stabilized by cocoa powder: Role of the emulsification process and of composition parameters

We fabricated oil-in-water emulsions stabilized by delipidated commercial cocoa powder. The emulsions were characterized in terms of droplets and particles size distribution and interfacial coverage by cocoa powder by developing methods to separate droplets from adsorbed and unadsorbed cocoa particles. Three different processes were compared for their ability to produce fine and stable emulsions: rotor/stator turbulent mixing, sonication and microfluidization. Among those techniques, microfluidization was the most performing one. In this case, micron-sized emulsions with narrow size distributions could be obtained with >90 wt% of the powder insoluble material anchored to the interfaces, and they were still stable after 90 days. It was demonstrated that the mixing process did not generate finer cocoa particles but provoked disentanglement of the large primary particles, providing them an open, expanded structure that facilitated emulsification. It was also shown that the finer insoluble fraction of the powder and the soluble fraction had no significant impact on emulsification and on kinetic stability. In the poor particles regime, the oil-water interfacial area varied linearly with the amount of adsorbed powder, suggesting that the final droplet size was controlled by the so-called limited coalescence process, as already observed in conventional Pickering emulsions stabilized by spherical solid particles.

On the geometric stability of an inorganic nanowire and an organic ligand shell

The break-up of a nanowire with an organic ligand shell into discrete droplets is analysed in terms of the Rayleigh-Plateau instability. Explicit account is taken of the effect of the organic ligand shell upon the energetics and kinetics of surface diffusion in the wire. Both an initial perturbation analysis and a full numerical analysis of the evolution in wire morphology are conducted, and the governing non-dimensional groups are identified. The perturbation analysis is remarkably accurate in obtaining the main features of the instability, including the pinch-off time and the resulting diameter of the droplets. It is conjectured that the surface energy of the wire and surrounding organic shell depends upon both the mean and deviatoric invariants of the curvature tensor. Such a behaviour allows for the possibility of a stable nanowire such that the Rayleigh-Plateau instability is not energetically favourable. A stability map illustrates this. Maps are also constructed for the final droplet size and pinch-off time as a function of two non-dimensional groups that characterise the energetics and kinetics of diffusion in the presence of the organic shell. These maps can guide future experimental activity on the stabilisation of nanowires by organic ligand shells.