Continuous and scalable polymer capsule processing for inertial fusion energy target shell fabrication using droplet microfluidics

Abstract

High specification, polymer capsules, to produce inertial fusion energy targets, were continuously fabricated using surfactant-free, inertial centralisation, and ultrafast polymerisation, in a scalable flow reactor. Laser-driven, inertial confinement fusion depends upon the interaction of high-energy lasers and hydrogen isotopes, contained within small, spherical and concentric target shells, causing a nuclear fusion reaction at ~150 M°C. Potentially, targets will be consumed at ~1 M per day per reactor, demanding a 5000x unit cost reduction to ~$0.20, and is a critical, key challenge. Experimentally, double emulsions were used as templates for capsule-shells, and were formed at 20 Hz, on a fluidic chip. Droplets were centralised in a dynamic flow, and their shapes both evaluated, and mathematically modeled, before subsequent shell solidification. The shells were photo-cured individually, on-the-fly, with precisely-actuated, millisecond-length (70 ms), uniform-intensity UV pulses, delivered through eight, radially orchestrated light-pipes. The near 100% yield rate of uniform shells had a minimum 99.0% concentricity and sphericity, and the solidification processing period was significantly reduced, over conventional batch methods. The data suggest the new possibility of a continuous, on-the-fly, IFE target fabrication process, employing sequential processing operations within a continuous enclosed duct system, which may include cryogenic fuel-filling, and shell curing, to produce ready-to-use IFE targets.

Microfluidic Devices in Fabricating Nano or Micromaterials for Biomedical Applications

“…The application of these QD‐encoded microparticles demonstrated the potential practicability in multiplexed biomolecular detection. Thus far, a diversity of other nanoparticles have been prepared using droplet‐based microreactors, including polymers, metal nanocrystals (Pd, Fe, Ag, Au), MOFs, and silica . Reactions occur in the microdroplet and can be used for epitaxial growth of particles with different shapes, including branched gold nanostars .…”

Glassy Microspheres for Energy Applications

“…The polymeric layers must have a predetermined thickness and a surface finish smoother than 0.1 μm and they must conform perfectly to the glass sphere; the deposition technique is therefore very important [ 114 , 126 , 127 ]. In recent years, laser-fusion programs seem to have moved to consider larger fuel capsules [ 121 , 128 ]; viable ICF targets are represented by spherical shells with diameter 0.5 to 4 mm, wall thickness 50–100 μm, low density (~250 mg/cm 3 ), with interconnected voids (each <1 μm diameter), with extreme sphericity (>99.9%, <50 nm roughness variation), and a high degree of concentricity (>99.0%) [ 129 ]. Fabricating these pellets with so stringent specifications is a big technical challenge, and even more challenging is the fact that they should be produced at massive scale.…”

“…The efforts to improve the quality of the targets [ 131 ] and to develop the possibility of their large-scale production have made significant progress in recent years. As an example, Li et al developed a continuous and scalable process for the fabrication of polymer capsules using droplet microfluidics, thus demonstrating that, even with the many remaining limitations, channel-based droplet microfluidics technology has the potential of being applied to ICF target fabrication [ 129 ].…”

Production of Highly Monodisperse Millimeter‐Sized Double‐Emulsion Droplets in a Coaxial Capillary Device

“…Double‐emulsion droplets have a significant potential for producing various microcapsules or other attractive candidates for a wide range of applications . Especially, the droplets ranging from 100 µm to a few millimeters are widely used in various areas, such as bioactive species delivery, controlled release, microreactors, heterogeneous catalysis, ion exchange, granular flow, and inertial confinement fusion (ICF) experiments . However, the millimeter‐scale double‐emulsion droplets were more vulnerable due to the complex rheology and the density stratification than micro‐scale ones.…”