Droplets and face coverings

Author: Pietro Cicuta
id: idea-20201008-01-v1
 
There was a lot of discussion in spring/summer 2020 on the efficiency of face coverings, and various types of masks, in reducing the spread of droplets. It seemed nobody quite knew if masks would have a big effect (they probably do, for a variety of reasons). An aerosol is a droplet so small that it stays floating in air, like fog. When we speak, or breathe, we emit aerosols. But we also emit larger droplets that travel straight, for some distance.

Various labs tried to make experiments. This here is not a review! We just point to a UK study https://arxiv.org/abs/2005.10720 which used an optical technique to enhance contrast (Background Oriented Schlieren) and also a study done at NIH that strikes us for its simplicity. A laser light was optically manipulated to make a "light sheet", and then the scattering of light from droplets emitted whilst speaking was captured by a smartphone, together with the audio of the person speaking. A very interesting video of the experiment is here. 

Imagine such a simple experiment being published in the New England Journal of Medicine, a publication with Impact Factor 74 !!! Shows what's possible with a good and important idea (and tools just need to be "good enough").

With the right lighting conditions, it might even be possible to do experiments imaging dropletswithout a laser light sheet? If the question is how far droplets fly, it might not be necessary to capture droplets in air… rather let droplets land (with food coloring?) on white paper, and measure their sizes and distances? Speaking or coughing through an opening into a box (with food coloring?), covering the inside of the box with white paper, could analysed to see in which directions droplets go?

These are, as far as we know, untested experiments in the context of student projects.

Benchtop experiments and frugal research

Author: Pietro Cicuta
id: idea-20201008-02-v1

Experiments in schools and early years of university need to be robust and cheap, and exciting. This has a lot in common with many other science activities. On one end are public outreach and citizen science. On another end is research faced with significant economic constraints. In developing countries, outside the best funded laboratories, scientists often turn into “theoreticians”, as they perceive too much difficulty in attempting experiment driven research. One cannot dispute that there are areas (advanced condensed matter physics; particle physics; molecular biology) that cannot be attempted on small budgets. However exciting new science is being done all the time also with very modest equipment. In the 80s and 90s, chaos was explored with simple electronic circuits. In the 90s, many key experiments in soft matter physics were published using cheap equipment (webcams) and consumer products (shaving foam and detergent foam drainage). Experiments on fluids have a very long tradition that continues these days with simple experiments on swimming micro-organisms, and granular matter studies have been with very simple kit. Cameras and computers have seen such drops in cost that one can look back at some experiments that were challenging and required special instruments a few decades ago, and can now be reproduced (better!) with a Raspberry Pi computer and its camera.

These concepts have motivated many researchers. Manu Prakash, in Stanford, is well known for having spoken many times about the value of “frugal research”. Another similar and large community has taken part over the last decade in the Hands-On-School, an annual graduate school aimed at early career PIs, post-docs and PhD students from developing countries, based around the message of empowering experimental research with bench-top experiments. We hope that many of the experiments demonstrated in the Hands On schools will be presented on the website here soon. In many cases they are flexible experiments that can take as little as a few hours in the form of a demonstration, but can be turned into longer investigations and even research projects. There is something to say about the power of bench-top experiments even in well funded labs. Often group leaders, and their students, can end up lining up their research questions to the unique/expensive pieces of equipment that they have. Ok, this is a good use of that equipment. But to make new discoveries, science research needs to be nurtured by curiosity, and it is important that skills and resources exist so that researchers can quickly set up and try out new experiments.