Coatings and surface treatment
to the surface Bubbling
Researchers from the University of Sydney Nano Institute and School of Chemistry have revealed that tiny gas bubbles – nanobubbles just 100 billionths of a meter high – form on surfaces in unexpected situations, providing a new way to reduce drag in small-scale devices. Kim
Thomas speaks to Professor Chiara Neto, who led the research, to find out how they made the discovery and what its implications are for the future of microfluidic devices.
the tiny, hair-width channel on a microchip and it can interact with a reagent to detect a biomarker and produce a diagnosis. This lab-on-a-chip is – in theory – highly portable and produces an instant result, enabling people to be diagnosed within their own homes, and avoiding the need to send samples to a laboratory. Such a device would be particularly useful in developing countries with limited laboratory facilities.
T
Over the past year or two, most of us have been using microfluidic devices regularly. The lateral flow tests used to diagnose Covid using just a nasal sample can now be found in almost every home. But these paper tests, while cheap and easy to mass produce, have low sensitivity. Diagnosis of many diseases requires a more sophisticated version of the lab-on-a-chip, using tiny channels encased in glass, silicon or polydimethylsiloxane. Deploying this type of microfluidic device successfully, however, involves overcoming the problem of frictional drag, caused by the fact that the liquid sticks on the wall of the capillary. The smaller the capillary, the bigger the problem: more of the liquid, relatively speaking, sticks to the solid walls. “When we start to go down to capillaries that are maybe 100 microns in diameter or less, then this effect becomes really strong,” says Chiara Neto, professor of physical chemistry at the University of Sydney. “And then it’s much more relevant to try and minimise that friction.”
102
he potential of microfluidic technology in medicine has been recognised for decades. Put a minute amount of blood or saliva into
Solving the friction problem To overcome the friction problem, the solution has so far been to use high pressures to drive the flow. As well as being inefficient, this high pressure can damage delicate samples in the device, such as cells and other soft materials. The solid walls can become fouled by biological molecules or bacteria, leading to fast degradation. A paper published earlier this year in Nature Communications, however, suggests that Neto and her University of Sydney colleagues, have found a way of reducing that frictional drag. The four-strong team consists of Neto herself, Chris Vega-Sánchez, a PhD student whose work focuses on this problem, Dr Sam Peppou-Chapman, an expert in liquid-infused surfaces, and Dr Liwen Zhu, an expert in atomic force microscopy, which enables scientists to see down to a billionth of a metre.
The problem of frictional drag is one that Neto herself has been thinking about since taking her PhD 20 years ago, and she has worked on it on and off ever since. “What I’m interested in is how we can tune the interaction of liquids with solids as we change either the surface structure or the surface composition of the solid,” she says. Over time she and her colleagues have made a lot of progress, culminating in the discovery made last year: “We’ve now probably hit on the most successful story that we’ll find on reducing drag.”
The lotus leaf effect
It is already well-known, Neto explains, that “by applying a microscopic or nanoscopic surface
Medical Device Developments /
www.nsmedicaldevices.com
LDarin/
Shutterstock.com
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104 |
Page 105 |
Page 106 |
Page 107 |
Page 108 |
Page 109 |
Page 110 |
Page 111 |
Page 112 |
Page 113 |
Page 114 |
Page 115 |
Page 116 |
Page 117 |
Page 118 |
Page 119 |
Page 120 |
Page 121 |
Page 122 |
Page 123 |
Page 124 |
Page 125 |
Page 126 |
Page 127 |
Page 128
