Optical Control of Emulsion Drops for Nanofluidics and Microfabrication
Lead Research Organisation:
Science and Technology Facilities Council
Department Name: Central Laser Facility (CLF)
Abstract
Abstracts are not currently available in GtR for all funded research. This is normally because the abstract was not required at the time of proposal submission, but may be because it included sensitive information such as personal details.
People |
ORCID iD |
| Andrew David Ward (Principal Investigator) |
Publications
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
(2015)
Microfluidic generation of monodisperse ultra-low interfacial tension oil droplets in water
in RSC Advances
Woods D
(2011)
Nanofluidic networks created and controlled by light
in Soft Matter
| 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 |
| URL | http://www.dur.ac.uk/soft.matter/research/optonanofluidics/ |
| 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. |
| Description | Imaging Interfacial Tension |
| Organisation | Loughborough University |
| Department | Department of Computer Science |
| Country | United Kingdom |
| Sector | Academic/University |
| PI Contribution | Successful application to STFC Central Laser Facility for 2 weeks of access time to further studies in this area |
| Collaborator Contribution | Discussion and design of novel experimental work. Drafting, refinement and submission of application for experimental time at the CLF. |
| Impact | Access has been granted to the Central Laser Facility. Experimental time will be compete in mid-June 2017. |
| Start Year | 2016 |
| Description | Laboratory Tours |
| Form Of Engagement Activity | Participation in an open day or visit at my research institution |
| Part Of Official Scheme? | No |
| Geographic Reach | Regional |
| Primary Audience | Policymakers/politicians |
| Results and Impact | Numerous tours including science board and PALS board Inreased awareness of LSF cross-campus activities |
| Year(s) Of Engagement Activity | 2010,2011 |
| Description | Marblar Optical Sculpting competition |
| Form Of Engagement Activity | Participation in an activity, workshop or similar |
| Part Of Official Scheme? | No |
| Geographic Reach | National |
| Primary Audience | Public/other audiences |
| Results and Impact | On-line competition, sponsered by RSC and open to the general public, aimed at generation of novel ideas to exploit optical deformation technology. Brainstorming of ideas on how the sculpting technology could be used |
| Year(s) Of Engagement Activity | 2012 |
| Description | STFC Open Days |
| Form Of Engagement Activity | Participation in an open day or visit at my research institution |
| Part Of Official Scheme? | Yes |
| Geographic Reach | International |
| Primary Audience | Public/other audiences |
| Results and Impact | Informing the general public of experiments that can be performed with lasers. Inspiring school children to take an interest in science. |
| Year(s) Of Engagement Activity | 2014 |