#viscoplasticity

[fuckyeahfluiddynamics]

Lung Flows

When a fluid coats the inner walls of a cylinder, it can move downward in what's called a collar flow. In our airways, a sinking collar flow can thicken as it falls, eventually blocking the airway completely.  (Image and research credit: J. Shemilt et al.; via APS)

[materialsscienceandengineering]

Liquid metal ink liberates form

Today's electronic devices strive for new form factors—to make them foldable, stretchable, and deformable. To produce such devices that are highly stretchable or deformable, it is necessary to develop electrodes and circuit lines whose electrical properties can withstand harsh deformation or mechanical damage. To this, POSTECH-Yonsei University joint research team has recently developed liquid metal ink to accelerate printed electronic devices that can be changed into any shape.

Professor Unyong Jeong and Dr. Selvaraj Veerapandian of POSTECH's Department of Materials Science and Engineering, with Professor Aloysius Soon and Dr. Woosun Jang of Yonsei University's Department of Materials Science and Engineering, have developed liquid metal microparticles with high conductivity and viscoplasticity. These research findings were published in the authoritative international journal Nature Materials on January 4, 2021.

Electronic devices conventionally use electrodes and circuit lines made of hard metals such as gold, silver, or copper. However, such metal substrates crack and lose their electrical conductivity upon external pressure and elongation, making them unfit to use in deformable electronic devices. On the contrary, liquid metals—which flow like a liquid at room temperature and are easily deformable and highly conductive—have attracted great attention for their potential applicability in stretchable circuit lines. However, when these liquid metals are made into ink, an insulating oxide skin forms on the surface that removes their conductivity after being printed.

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[fuckyeahfluiddynamics]

Viscoplastic Drop Impact

There are many materials that don't behave exactly as a fluid or a solid, instead displaying characteristics of both. In this video, we see drops of hair gel falling into water. The gel is viscoplastic - showing some of the viscous behavior of a fluid and some of the plastic behavior (the inability to change back to its initial shape) of a solid. (Image and video credit: M. Jalaal et al.) Read the full article