Optical Control of Emulsion Drops for Nanofluidics and Microfabrication
Lead Research Organisation:
Imperial College London
Department Name: Chemistry
Abstract
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Organisations
Publications
Woods D
(2011)
Nanofluidic networks created and controlled by light
in Soft Matter
Bolognesi G
(2015)
Microfluidic generation of monodisperse ultra-low interfacial tension oil droplets in water
in RSC Advances
Bolognesi G
(2016)
Mechanical Characterization of Ultralow Interfacial Tension Oil-in-Water Droplets by Thermal Capillary Wave Analysis in a Microfluidic Device.
in Langmuir : the ACS journal of surfaces and colloids
Bolognesi G.
(2014)
A microfluidic platform for the production of monodisperse ultralow interfacial tension oil droplets in water
in 18th International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2014
| Description | The project was divided into four workstreams on optics, chemistry, microfluidic engineering and theory. These workstreams were then brought together to address the key objectives of the project. We briefly address the technical developments in each of the workstreams and then how the workstreams were integrated. (i) Optics Spatial light modulators were used to create multiple traps to shape droplets in 2 and 3 dimensions and to create nanofluidic networks in 2 and 3 dimensions. Two methods for measuring the 3D shape of deformed droplets were implemented: confocal microscopy at the LSF at RAL and structured illumination at Durham. A rig was developed for UV polymerisation of trapped droplets with Raman detection of the progress of the polymerisation reaction. A FRAP (fluorescence recovery after photo-bleaching) experiment was developed to measure the flow rate through nanothreads. (ii) Chemistry The phase behaviour of both temperature-sensitive and temperature-insensitive microemulsion formulations was characterised. The effect of polymers on the interfacial tension (IFT) was explored in the ultralow IFT (ULIFT) regime. (iii) Microfluidic engineering Microfluidic devices were developed comprising a flow-focussing junction (FFJ) for generation of oil droplets and an observation chip (ObC) for deforming them. The design allows the generation of monodisperse 3-10 µm drops at moderate IFT and the transfer of these droplets to the Peltier-controlled ObC where ULIFT is achieved, based on the phase behaviour determined in the 'chemistry' workstream. Both temperature and salinity can be used to control interfacial tension across four orders of magnitude. In addition, a microfludic tensiometry technique for the quantitative characterisation of the mechanical properties of the ultralow interfacial tension droplets was developed. We combined the microfluidic platform for droplet generation with the analysis of thermally-driven capillary waves/fluctuation analysis for the measurement of ULIFT and the results compared with literature data from spinning drop tensiometry. (iv) Theory A numerical 'spokes' model was implemented to compute the shape of a droplet in one or more optical traps. An analytical asymptotic model for droplet deformation in a single trap was developed and compared with the numerical model. The effects of buoyancy were added to the theoretical model. A theoretical model for flow through nanothreads was developed, which places an upper limit of the length of the nanothread through which fluid can be pumped using optical pressure from the trapping lasers. Integration (i) A parametric study was completed on the formation of droplets in an FFJ as a function of salinity and temperature in an AOT/brine/heptane system. Droplet generation is possible even in the ULIFT regime if interface is created faster than surfactant can adsorb to the nascent interface. (ii) The effect of laser heating on trapped droplets was modelled in Comsol and the consequences for the behaviour of temperature-insensitive emulsions in an optical trap was explored experimentally. Intriguing behaviour including the spontaneous generation of new phases was observed and explained in terms of the phase diagram of the quinary mixture. (iii) The deformed shape of a single droplet in an optical trap was measured experimentally, including the observation of the theoretically predicted hour-glass shape. Experimental shapes were compared with theoretical predictions. (iv) The shapes of droplets were characterised for three or four traps in a plane as a function of the optocapillary number (a dimensionless parameter that measures the relative strength of optical and capillary forces). The formation of a tetrahedron with out-of-plane traps was attempted. The importance of incorporating buoyancy and spherical aberration in theoretical models and practical implementation of droplet shaping strategies was highlighted. (v) Initial experiments on the production of connected nanodroplet networks in 3D were successfully conducted |
| Exploitation Route | In the short term, we plan to bring to a conclusion the objectives of the project that were not fully attained: specifically, (i) optimisation of the strategy for shaping droplets in 3-D; (ii) measurement of polymerisation kinetics in trapped droplets and optimisation of strategy for maintaining ULIFT during polymerisation; (iii) generation and characterisation of 3D nanodroplet networks, involving 4-way junctions and closed loops. In the longer term, shaped microparticles have potential applications in medical devices, specialist coatings, drug delivery, micromechanical systems, photonic materials and ion sources. Nanofluidic networks could also be used as a means of performing chemical reactions using only tiny volumes of the chemicals. Our main route for exploitation is using the optical deformation of polymerisable emulsions of monomers as a technology for microfabrication of objects with complex 3-D shapes. Nanofluidic networks could also be exploited in as a means of performing chemical reactions on the attolitre scale and we are exploring this opportunity through follow-on funding. |
| Sectors | Chemicals,Healthcare,Pharmaceuticals and Medical Biotechnology |
| Description | The key aims of the grant have been to develop novel high-throughput strategies for the manufacture of ultra-low tension droplets with control of size and composition. In the presence of optical traps ultra-low tension droplets (ULTDs) can be sculpted; such that their shape can be controlled. We have made excellent progress with respect to the generation of ULTDs and the integration of these systems with the optical trapping assemblies. In parallel excellent progress has been made with respect to modelling the behaviour of ULTDs. Building on this foundation we have been exploring applications of ULTDs as building motifs for chemical reactors and shaped nanoparticles. This has included the construction of 3-D nano-networks that can be used as the basis for controlled sequential reactions exploiting oil based chemistries. The ability to manufacture such oil based "labs on a chip" where reagents can systematically be added to a reaction chamber has already attracted strong interest from the biotech sector. Extended capabilities of these systems by incorporating molecular rotors. This technology was initially developed for ultra-low tension droplets in water and expanded to develop compartmentalised systems that could be used as sequential chemical reactors. This approach however also in parrallel inspired the development of compartmentalised systems where lipid bilayers seperate aqueous sub-compartments - vesicle interface bilayers being amongst the technologies that emerged. Via this approach we demonstrated it is possible to use optical tweezers to assemble and dismantle vesicles assemblies. These vesicles are connected through double-bilayer junctions with chemically distinct vesicles linked across length scales from several nanometres to hundreds of micrometres by axon-like tethers. Optical trapping is used to construct these assembles and laser triggered vesicle merging can be affected. As a result we can mix and dilute content between different compartments. This system has enabled us to create novel architectures that replicate key motifs seen in biology such as immune synapses which in turn are opening up new approaches for studying biological systems using bottom-up approaches for studying how therapeutics in industry interact with biological membranes. |
| First Year Of Impact | 2018 |
| Sector | Chemicals,Healthcare,Pharmaceuticals and Medical Biotechnology |
| Impact Types | Economic |
| Description | Mass Transport in Ultralow Interfacial Tension Droplet-Nanothread Networks (DNNs) |
| Amount | £30,000 (GBP) |
| Funding ID | 17,330,050 |
| Organisation | Rutherford Appleton Laboratory |
| Sector | Academic/University |
| Country | United Kingdom |
| Start | 02/2018 |
| End | 06/2018 |
| Description | Molecular rotors as quantitative probes of interfacial tension |
| Amount | £30,000 (GBP) |
| Funding ID | 16,230,049 |
| Organisation | Rutherford Appleton Laboratory |
| Sector | Academic/University |
| Country | United Kingdom |
| Start | 02/2017 |
| End | 06/2017 |
| Description | Translational grant (Pathways to Impact funding) |
| Amount | £132,000 (GBP) |
| Organisation | Engineering and Physical Sciences Research Council (EPSRC) |
| Sector | Public |
| Country | United Kingdom |
| Start | 12/2015 |
| End | 11/2016 |
| Title | Fabrication of nanofluidic networks using optical traps |
| Description | By using a time-sharing optical trapping system combined to our microfluidic platform, we optically manipulated ultralow interfacial tension droplets (5µm in diameter) in order to create and control in real-time user-defined three-dimensional nanofluidic networks. |
| Type Of Technology | New/Improved Technique/Technology |
| Year Produced | 2015 |
| Impact | Closed-loop networks as well as nanothread Y junctions were achieved. |
| Title | Image analysis software for characterising ULIFT droplets |
| Description | We developed a class of image analysis software, based on Python code and Image Java macros, to characterise ULIFT droplet populations. The analysis of images captured through standard and high-speed digital video microscopy enabled the determination of i) distributions of droplet diameters ii) distributions of levels of droplet deformation iii) droplet generation frequencies iv) droplet speeds. |
| Type Of Technology | Software |
| Year Produced | 2013 |
| Impact | The analysis of images captured through standard and high-speed digital video microscopy enabled the determination of i) distributions of droplet diameters ii) distributions of levels of droplet deformation iii) droplet generation frequencies iv) droplet speeds. |
| Title | Microfluidic generator for ULIFT droplets |
| Description | We developed a microfluidic platform, consisting of s droplet generator device coupled to custom built observation/manipulation chamber chip, to generate, manipulate and characterise micron-sized heptane droplets in NaCl-Aerosol OT(surfactant) solutions. |
| Type Of Technology | New/Improved Technique/Technology |
| Year Produced | 2014 |
| Impact | By varying the geometry of the droplet generator device and the flow rates of the liquid phases, we could obtain i) monodisperse populations of large droplets with diameters ranging from 11µm to 40µm, ii) monodisperse populations of small droplets with diameters ranging from 5µm to 8µm iii) bidisperse population of main and satellite droplets with diameters ranging from 11µm to 20µm and from 2µm to 4µm, respectively. |
| Title | Microfluidic platform for the generation of micron sized ultra-low tension droplets |
| Description | Microfluidic platform for the generation of micron sized ultra-low tension droplets. Fully automated-able to modulate size and composition of ultra-low tension droplets as well as provide an observation chamber for their manipulation using optical traps. |
| Type Of Technology | New/Improved Technique/Technology |
| Year Produced | 2013 |
| Impact | User defined capabilities for manufacturing ULITD for the first time. |
| Title | Microfluidic strategy for tuning interfacial tension of droplets |
| Description | We devised a microfluidic strategy based on on-chip control of the emulsion temperature and salinity level, which enabled the active tuning of the droplet equilibrium and dynamic interfacial tensions over a range spanning four orders of magnitudes (namely, from 10-7 N/m to 10-3 N/m). |
| Type Of Technology | New/Improved Technique/Technology |
| Year Produced | 2015 |
| Impact | By adjusting the oil-brine interfacial tension according to the microfluidic operation required (e.g. droplet generation, transport, storage), we could manufacture monodisperse droplet populations in the low (<10-3N/m) and ultralow (<10-3N/m) interfacial tension regimes with high levels of droplet stability with respect to rupture and coalescence rates. |
| Title | Microfluidic tensiometry |
| Description | We developed and validated a microfludic tensiometry technique for the quantitative characterisation of the mechanical properties of ultralow interfacial tension droplets. |
| Type Of Technology | New/Improved Technique/Technology |
| Year Produced | 2015 |
| Impact | We combined our microfluidic platform for droplet generation with the analysis of thermally-driven capillary waves, observed at the droplet equatorial plane through bright field microscopy, in order to measure both the droplet interfacial tension and the surfactant film bending rigidity. The microfluidic tensiometry measurements were in good agreement with the literature data. |
| Title | Model for simulating droplet generation in microfluidic chips |
| Description | Two-dimensional finite-element simulations of droplet generation in cross-junction devices were performed through Comsol Multiphysics®. |
| Type Of Technology | Software |
| Year Produced | 2014 |
| Impact | The two-phase flow dynamics and the droplet break-up process were simulated by solving the Stokes equations (Momentum and mass conservation) and the Level set equation through the Comsol microfluidics module. The outcome of the numerical simulations in terms of droplet size and generation frequency were qualitatively in good agreement with the experimental results. |
| Title | model for simulating effect of laser induced heating on ULIFT droplets |
| Description | Two-dimensional axisymmetric models were developed in Comsol Multiphysics®. to investigate the effect of laser-induced heating on ultralow interfacial tension droplets under optical traps. |
| Type Of Technology | Software |
| Year Produced | 2014 |
| Impact | The heat equation was solved for heptane droplets both spherical and deformed, heated by Gaussian laser beams and immersed in either water or deuterium oxide bulk phases. The model inputs were i) the laser beam intensity profile - obtained from numerical solutions of the Maxwell equations (in the modelling and control work stream) and ii) the deformed droplet shapes - experimentally obtained through structured illumination measurements (in the optics work stream). The model outputs were the temperature and the interfacial tension profiles at the droplet interfaces. |
| Title | optical trapping technique to qualitatively assess and compare the deformability of micron-sized ultralow interfacial tension droplets |
| Description | We introduced an optical method based on time-sharing optical trapping technique to qualitatively assess and compare the deformability of micron-sized ultralow interfacial tension droplets. |
| Type Of Technology | New/Improved Technique/Technology |
| Year Produced | 2015 |
| Impact | Two optical traps were used to stretch the droplets by pulling them from two opposite ends. By analysing the droplet deformed shapes under varying salinity and laser power levels, the droplet interfacial tension was qualitatively estimated. Our measurements were in good agreement with the literature data. |
| Description | Conference presentation |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Professional Practitioners |
| Results and Impact | Royal Society meeting entitled "The artificial cell: biology inspired compartmentalisation of chemical function" |
| Year(s) Of Engagement Activity | 2018 |
| URL | https://royalsociety.org/science-events-and-lectures/2018/02/artificial-cell/ |
| Description | Conference presentation |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | National |
| Primary Audience | Professional Practitioners |
| Results and Impact | "Droplet-based functional materials for biochemical studies and applications" at 1st Meeting of UK Fluids Network Special Interest Group (SIG) on Fluid Mechanics of Nanostructured Materials |
| Year(s) Of Engagement Activity | 2018 |
| Description | Conference presentation at Chains 2018 |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Professional Practitioners |
| Results and Impact | Presentation on Artificial Cells and Compartmentalisation at Chains 2018, December 2017 |
| Year(s) Of Engagement Activity | 2017 |
| URL | http://www.nwochains.nl/ |
| Description | International Microfluidics Congress |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Professional Practitioners |
| Results and Impact | International conference: disseminate findings of research and look for new end users of the technology |
| Year(s) Of Engagement Activity | 2015 |
| Description | Presentation entitled "A microfluidic platform for the mechanical property characterisation of ultralow interfacial tension droplets"at British Society of Rheology Winter Meeting 2015 |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | National |
| Primary Audience | Other academic audiences (collaborators, peers etc.) |
| Results and Impact | Dissemination of results to new end users Successful presentation of new microfluidic device to potential end users |
| Year(s) Of Engagement Activity | 2015 |
| Description | Presentation entitled "A microfluidic platform for the production of monodisperse ultralow interfacial tension oil droplets in water"at Micro-TAS 2014 |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Other academic audiences (collaborators, peers etc.) |
| Results and Impact | Dissemination of results to new end users Successful presentation of new microfluidic device to potential end users |
| Year(s) Of Engagement Activity | 2014 |
| Description | Presentation entitled "Formation of monodisperse ultra-low interface tension droplets with a microfluidic flow focusing device" at Flow 14 (2014) |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Other academic audiences (collaborators, peers etc.) |
| Results and Impact | Dissemination of results to new end users Successful presentation of new microfluidic device to potential end users |
| Year(s) Of Engagement Activity | 2014 |
| Description | Presentation entitled "Microfluidic generation and optical manipulation of ultra-low interfacial tension droplets" at Compartmentalisation & Confinement in Biological Systems 2015 |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | National |
| Primary Audience | Other academic audiences (collaborators, peers etc.) |
| Results and Impact | Dissemination of results to new end users Successful presentation of new microfluidic device to potential end users |
| Year(s) Of Engagement Activity | 2015 |
| Description | Presentation entitled "Microfluidic generation and optical manipulation of ultra-low interfacial tension droplets" at Global Engage's Microfluidics Congress 2015 |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Other academic audiences (collaborators, peers etc.) |
| Results and Impact | Dissemination of results to new end users Successful presentation of new microfluidic device to potential end users |
| Year(s) Of Engagement Activity | 2015 |
| Description | Presentation entitled "Microfluidic generation and optical manipulation of ultra-low interfacial tension droplets"at SPIE Microtechnologies 2015 |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Other academic audiences (collaborators, peers etc.) |
| Results and Impact | Dissemination of results to new end users Successful presentation of new microfluidic device to potential end users |
| Year(s) Of Engagement Activity | 2015 |
| Description | Presentation to the general public (Friends of Imperial College) |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | Local |
| Primary Audience | Public/other audiences |
| Results and Impact | Presentation aimed at addressing public concerning associated with manufacturing artificial cells and manipulating biological systems. |
| Year(s) Of Engagement Activity | 2015 |
| Description | Technology showcase presentation to industry (AstraZeneca) |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | National |
| Primary Audience | Industry/Business |
| Results and Impact | Workshop and associated talk aimed at translating EPSRC breakthrough to industry. |
| Year(s) Of Engagement Activity | 2015 |