Waterloo Institute for Nanotechnology

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Browsing Waterloo Institute for Nanotechnology by Subject "adhesion"

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    Microparticle suspensions and bacteria laden droplets: Are they the same in terms of wetting signature?
    (ACS, 2021-01-17) Melayil, Kiran Raj; Misra, Sirshendu; Mitra, Sushanta K.
    Adhesion behavior of microbial pathogens on commonly encountered surfaces is one of the most pertinent questions now. We present the characterization of bacteria laden droplets and quantify the adhesion forces on highly repellent surfaces with the help of a simple experimental setup. Comparing the force signature measured directly using an in-house capillary deflection based droplet force apparatus, we report an anomalous adhesion behavior of live bacteria (E. coli) laden droplets on repellent surfaces, which stands in stark contrast to the observed adhesion signature when the doping agent is changed to inert microparticles or the same bacteria in an incapacitated state. We showed that the regular contact angle measurements using optical goniometry is unable to differentiate between the live bacteria and the dead ones (including microparticles) and thus delineate its limitations and the complementary nature of the adhesion measurements in understanding the fundamental interfacial interaction of living organisms on solid surfaces.
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    Wetting, adhesion and droplet impact on face masks
    (ACS, 2021-02-12) Melayil, Kiran Raj; Mitra, Sushanta K.
    In the present pandemic time, face masks are found to be the most effective strategy against the spread of the virus within the community. As aerosol-based spreading of the virus is considered as the primary mode of transmission, the interaction of masks with incoming droplets needs to be understood thoroughly for an effective usage among the public. In the present work, we explore the interactions of the droplets over the most commonly used 3-ply surgical masks. A detailed study of the wetting signature, adhesion and impact dynamics of water droplets and microbe-laden droplets is carried out for both sides of the mask. We found that the interfacial characteristics of the incoming droplets with the mask are very similar for the front and the back side of the mask. Further, in an anticipated attempt to reduce the adhesion, we have tested masks with a superhydrophobic coating. It is found that a superhydrophobic coating may not be the best choice for a regular mask as it can give rise to a number of smaller daughter droplets and thus can linger in air for longer time and can contribute to the transmission of potential viral loads.