The dynamic microfluidics laboratory is very flexible in its research. We have a large range of topics that we study all aided with our high speed cameras.
Drops and Micropatterns
Drop impacts have rich complexity and intrinsic beauty. We have studied the impact of water drops on leaves , sands and soils , and we are working to survey drop impacts on polymer micro-pillars . These pillars are made on-site using soft lithography, and various patterns can be designed. We have developed customised equipment, experimental methods, and image analysis processes for these experiments .
Impacts in Spray-Drying
We are currently working on a project to better understand impact of partially dried milk drops on stainless steel (and fouled surfaces, as in the optical profiler image) at raised temperatures. This study is important for spray-drying, which is the process used to produce milk powder (NZ’s largest export commodity) and related premium products. Enquiries from industry are welcome for projects such as this one.
Capillarity is a key feature of everyday processes such as liquid transport in plants, wicking into textiles, and printing. Capillary uptake is most simply observed when liquid is drawn into a tube. We use high-speed photography to study interesting cases, such as when the tube-liquid interaction is non-wetting (e.g. a teflon tube in contact with water), or when uptake is encouraged by the curvature of a droplet outside the tube .
 Fritsch, A., Willmott, G. R. & Taylor, M. Superhydrophobic New Zealand leaves: contact angle and drop impact experiments. Journal of the Royal Society of New Zealand 43, 198-210 (2013).
 Lardier, N., Roudier, P., Clothier, B. & Willmott, G. R. Spread, Cratering and Penetration during Water Drop Impacts on Sand and Soil. European Journal of Soil Science 70, 245-256 (2019).
 Robson, S. & Willmott, G. R. Asymmetries in the spread of drops impacting on hydrophobic micropillar arrays. Soft Matter 12, 4853-4865 (2016).
 Broom, M. A. J. & Willmott, G. R. High Throughput Analysis of Liquid Droplet Impacts. J. Vis. Experiments (in press).
 Willmott, G. R., Neto, C. & Hendy, S. C. Uptake of water droplets by non-wetting capillaries. Soft Matter 7, 2357-2363 (2011).