Uploaded July 2023 | Updated September 2026, 1 week ago
Timelapse movie of a green Ni(OH)2 membrane that grew in a horizontally positioned microfluidic channel. The left frames come directly from optical microscopy; the right ones are image-processed copies where an intensity threshold was applied to emphasize change.
The big upper and small lower gray bands are NiCl2 and NaOH solutions. In this time-lapse video, both solution flows are suddenly stopped and the membrane growth ceases within a few minutes.
The cool thing is the flickering. These are tiny colloidal particles of Ni(OH)2 that initially were too small to be detected by any optical microscope. However, once the flow is stopped, the membrane still releases OH- into the upper Ni2+ solution, which continues to feed their growth. At some point, they get big enough to be detected and zoom back and forth through optical focus, thus, causing the flickering. Towards the end, they get bigger and bigger and start to sediment.
We believe that during regular membrane growth (i.e. flowing solutions), the "invisible" nanoparticles are caught by the advancing interface. This process creates mesoscale patterns in the membrane, specifically dendrites and bands that appear as dark light-scattering features. If you watch carefully you can see initially black aggregation spots moving leftwards over the interface.
The field of view is about 100x400 um2 (stretched horizontally). Gravity goes "into the image".
This work is by Jessica Nogueira et al. and was published in Angew. Chem. (2023): doi.org/10.1002/anie.202306885
Timelapse movie of a green Ni(OH)2 membrane that grew in a horizontally positioned microfluidic channel. The left frames come directly from optical microscopy; the right ones are image-processed copies where an intensity threshold was applied to emphasize change.
The big upper and small lower gray bands are NiCl2 and NaOH solutions. In this time-lapse video, both solution flows are suddenly stopped and the membrane growth ceases within a few minutes.
The cool thing is the flickering. These are tiny colloidal particles of Ni(OH)2 that initially were too small to be detected by any optical microscope. However, once the flow is stopped, the membrane still releases OH- into the upper Ni2+ solution, which continues to feed their growth. At some point, they get big enough to be detected and zoom back and forth through optical focus, thus, causing the flickering. Towards the end, they get bigger and bigger and start to sediment.
We believe that during regular membrane growth (i.e. flowing solutions), the "invisible" nanoparticles are caught by the advancing interface. This process creates mesoscale patterns in the membrane, specifically dendrites and bands that appear as dark light-scattering features. If you watch carefully you can see initially black aggregation spots moving leftwards over the interface.
The field of view is about 100x400 um2 (stretched horizontally). Gravity goes "into the image".
This work is by Jessica Nogueira et al. and was published in Angew. Chem. (2023): doi.org/10.1002/anie.202306885
