Precisely shaped polymeric particles and structures are widely used for applications in photonic materials, MEMS, biomaterials and self-assembly. Current approaches for particle synthesis are either batch processes or flow-through microfluidic schemes that are based on two-phase systems, limiting the throughput, shape and functionality of the particles. We report a one-phase method that combines the advantages of microscope projection photolithography and microfluidics to continuously form morphologically complex or multifunctional particles down to the colloidal length scale. Exploiting the inhibition of free-radical polymerization near PDMS surfaces, we are able to repeatedly pattern and flow rows of particles in less than 0.1 s, affording a throughput of near 100 particles per second using the simplest of device designs. Polymerization was also carried out across laminar, co-flowing streams to generate Janus particles containing different chemistries, whose relative proportions could be easily tuned. This new high-throughput technique offers unprecedented control over particle size, shape and anisotropy.

Using experiments and simulations, we investigate the clusters that form when colloidal spheres stick irreversibly to -or "park" on -smaller spheres. We use either oppositely charged particles or particles labeled with complementary DNA sequences, and we vary the ratio α of large to small sphere radii. Once bound, the large spheres cannot rearrange, and thus the clusters do not form dense or symmetric packings. Nevertheless, this stochastic aggregation process yields a remarkably narrow distribution of clusters with nearly 90% tetrahedra at α = 2.45. The high yield of tetrahedra, which reaches 100% in simulations at α = 2.41, arises not simply because of packing constraints, but also because of the existence of a long-time lower bound that we call the "minimum parking" number. We derive this lower bound from solutions to the classic mathematical problem of spherical covering, and we show that there is a critical size ratio α c = (1 + √ 2) ≈ 2.41, close to the observed point of maximum yield, where the lower bound equals the upper bound set by packing constraints. The emergence of a critical value in a random aggregation process offers a robust method to assemble uniform clusters for a variety of applications, including metamaterials.

Coalescence of two kinds of pre-processed droplets is necessary to perform chemical and biological assays in droplet-based microfluidics. However, a robust technique to accomplish this does not exist. Here we present a microfluidic device to synchronize the reinjection of two different kinds of droplets and coalesce them, using hydrostatic pressure in conjunction with a conventional syringe pump. We use a device consisting of two opposing T-junctions for reinjecting two kinds of droplets and control the flows 10 of the droplets by applying gravity-driven hydrostatic pressure. The hydrostatic-pressure operation facilitates balancing the droplet reinjection rates and allows us to synchronize the reinjection. Furthermore, we present a simple but robust module to coalesce two droplets that sequentially come into the module, regardless of their arrival times. These re-injection and coalescence techniques might be used in lab-on-chip applications requiring droplets with controlled numbers of solid materials, which can be 15 made by coalescing two pre-processed droplets that are formed and sorted in devices.

I N TRODUC TIONUpper gastrointestinal (UGI) cancers, specifically oesophageal and gastric cancers, account for almost 10% of new cancer cases globally and approximately 13% of cancer mortality. 1 Surgical resection, with or without neoadjuvant and adjuvant therapies, remains the basis of curative intent treatment for this cancer group. These procedures are significant and not without a high risk of complications, such as anastomotic leak and impacts on morbidity, mortality and quality of life (QOL), which are of significant concern to medical teams. [2][3][4][5] Post major UGI surgery, enteral or parenteral nutrition or the timing or type of oral diet, is a significant consideration known to affect postoperative recovery and the ability to tolerate adjuvant treatment. 5 Despite its importance, there

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