Nanofluidic Cells with Controlled Pathlength and Liquid Flow for Rapid, High-Resolution In Situ Imaging with Electrons

Abstract

The use of electron probes for in situ imaging of solution phase systems has been a long held objective, largely driven by the prospect of atomic resolution of molecular structural dynamics relevant to chemistry and biology. Here, we present a nanofluidic sample cell with active feedback to maintain stable flow conditions for pathlengths varying from 45 nm to several 100 nm, over a useable viewing area of 50 x 50 μm. Using this concept, we demonstrate nanometer resolution for imaging weakly scattering polymer and highly scattering nanoparticles side by side with a conventional transmission microscope. The ability to flow liquids allows control over sample content and on-the-fly sample exchange, opening up the field of high-throughput electron microscopy. The nanofluidic cell design is distinguished by straightforward, reliable, operation with external liquid specimen control for imaging in (scanning) transmission mode and holds great promise for reciprocal space imaging in femtosecond electron diffraction studies of solution phase reaction dynamics

Opportunities and challenges in liquid cell electron microscopy

“…The spacer may be a solid layer with a channel, or spherical particles. The liquid may be inserted through an entry port etched into one chip (14)(15)(16)(17)(18) or flowed in through the gap between the chips (19). Electrodes can be patterned lithographically inside the closed cell and controlled by an external potentiostat (14).…”

“…In many designs, it also provides the vacuum seal by clamping the chips and supplies the liquid through inlet and outlet tubes driven by a syringe pump. Flow enables exciting possibilities of replenishing or changing the solution chemistry while imaging (15,19,30).…”

Through a Window, Brightly: A Review of Selected Nanofabricated Thin-Film Platforms for Spectroscopy, Imaging, and Detection

“…42,167 There is considerable variability and flexibility-depending on acceptable performance specifications-in the construction of devices using thin-film windows in a Si frame (e.g., SiN x , SiO 2 4,6-10, 186,187 ), including using hand-applied epoxy as spacer and for bonding (for a $5 mm gap), hand-applied nanoparticles as spacers, and patternable photoresist spacers. 20,[36][37][38]40,42,43,179,188 Recent advances in materials science have broadened the choice of window materials beyond traditional nanofabrication materials and, in a sense, have resurrected the use of thin, carbon-based films. The principal advantage of such a material choice is of course that the low (average) atomic number and low atomic density have salutary effects on image contrast and resolution.…”

Tracking reaction dynamics in solution by pump–probe X-ray absorption spectroscopy and X-ray liquidography (solution scattering)

“…Ultimately, it is desirable to develop nanofluidic cells for flowing samples, and several promising approaches have been proposed with recent technological advances. [189][190] …”