MRT letter: Micro‐ to nanoscale sample collection for high throughput microscopy

Abstract

In high throughput microscopy, it is often assumed that the objects under investigation are fixed spatially. In addition, it is also presumed that the objects are sufficiently populated, otherwise there will be need to search through vast tracks of field of views before any recording can be done. The ability to collect objects at one location in the hydrated state is thus desirable and this is a challenge when the density of target objects in a sample is very low. In this work, we report that the generation of a squeezing flow from a circular coverslip compressing on suspensions is able to collect particulate (microbeads, fluorescent nanobeads and live algal cells) and non-particulate (EGFP) objects at the rim region of the coverslip. With a coverslip of 13 mm diameter, volumes between 2 µL and 4 µL were found to completely fill the coverslip without breaching the rims. Sample compression speeds between 100 µm/s and 1000 µm/s did not have any effect on object collection outcomes. In effect, the simple placement of coverslips on top the drop of sample by hand without a motorized translator was found to produce similar collection outcomes. Quantitative measurements confirmed that all the objects investigated were displaced and relocated at the rim regions to a very high degree.

Scale-like cantilever cell traps

“…In doing so, it presents a different pathway to creating devices in applications such as the capture of circulating tumor cells, in which 3D-nanostructured substrate coated with cancer cell capture agents are effective but typically applied within closed channel uidic networks. 30 The recent ability to concentrate particles at the moving contact line even as a drop undergoes a squeeze ow from a sandwich 31,32 coupled with nanostructures created at the scale-like interface are possible future developments for this trapping approach. This could also benet from the feature of low sample loss when highly non-wetting elements are used to generate the squeeze ow.…”

Concentrating nanoparticles in environmental monitoring

“…When the appropriate droplet volume is reached, it can be easily transferred using a light puff of air (Vuong et al 2015) from the well to a microscope slide (Fig. 1B) where the approach previously reported (Cheong et al 2013) is used to bring the concentrated nanoparticles to the edge of the circular coverslip for microscopic imaging.…”

“…Detection methods can include the use of microscopy-related techniques such as environmental scanning electron microscopy (ESEM) (Muscariello et al 2005) particles concentrated at the coverslip rim (Cheong et al 2013, Cheong et al 2014. While this approach benefited from the squeeze flow concentration effect, it may be necessary to obtain a means to achieve imaging and detection modalities for samples that harbor extremely low concentrations of nanoparticles.…”

Modeling and fabrication of scale-like cantilever for cell capturing

“…In doing so, it presents a different pathway to creating devices in applications such as the capture of circulating tumor cells, in which 3D-nanostructured substrate coated with cancer cell capture agents are effective but typically applied within closed channel fluidic networks 24 . The recent ability to concentrate particles at the moving contact line even as a drop undergoes a squeeze flow from a sandwich 25,26 coupled with nanostructures created at the scale-like interface are possible future developments for this trapping approach. This could also benefit from the feature of low sample loss when highly non-wetting elements are used to generate the squeeze flow 21 .…”