The liquid-cell/micro-chamber was produced by sealing the sample between two Formvar plastic films. A NaCl sample (~99.5%) containing ~0.5% calcium silicate (MORTON table salt, Morton Salt Inc., Chicago, IL, USA) was used for the experiment, and a pure NaCl control (~99.999%, Sigma-Aldrich Co., St. Louis, MO, USA; ID: 450006, CAS: 7647-14-5) was used as a control to identify the role of the calcium silicate in the chamber. After dissolving 20 g of each sample in 40 mL of deionized water at room temperature, a ~1 mL aliquot of the saturation solution was collected from the surface into a 1 mL vial after centrifuged at 13,000 rpm for 5 min to separate the undissolved salt crystals from the solution. The saturated solution was then used for experimentation (Fig. 1A).

Assembly of the specimen for imaging liquid by a transmission electron microscope (TEM) Schematics of the assembled liquid-cell/micro chamber, in which (A) a saturated solution of sodium chloride (NaCl) was loaded onto (B) a Formvar plastic film that was pre-coated on a 200-mesh TEM grid. (C) Expanding the liquid solution to generate microscale crystals. The crystals were then sandwiched between two Formvar plastic films. (D) Under a light microscope, the sample was loaded on a grid and then sandwiched by aligning the grids on a washer. (E) The grids were subjected to physical pressure to ensure the crystals were sandwiched tightly. (F) The equipment used for compressing the grids under a controlled pressure. (G) A Zeiss Libra 120 TEM used for real-time video acquisition. (H) The grids were mounted on a regular TEM holder and examined by electron beam passing through the samples. (J) Representative TEM image of a chamber sealed two adhered rectangular NaCl crystals. (K,L) Two representative TEM images of electron beam irradiated NaCl for observing the liquid, vapor and clusters of nanoparticles. (I) Schematics of the three-dimensional (3D) shape of the liquid fluid within a chamber. Fig. A, B, C, G, E were prepared by Microsoft Office 10.0, Fig. I was drawn by SKETCHUP software (https://www.sketchup.com/), and Fig. J, K and L were the frames acquired with an OriusSC2006 CCD camera by GATAN Digital Micrograph.

An aliquot of the ~0.35 μL saturated NaCl solution was pipetted onto the center of a 200-mesh TEM copper pre-coated with a thin Formvar film (Cu-200F, Pacific Grid-Tech, San Francisco, CA, USA) (Fig. 1B). The second Formvar-coated 200-mesh TEM copper grid face-to-face was touched to the solution surface and expanded it to evaporate the solution quickly, generating micron-sized NaCl crystals (Fig. 1C), and then aligned under a light microscope (Fig. 1D). The aligned grids were submitted for compression under a pressure of 12 lb/in2 (~0.8 atm) for ~30 s (Fig. 1E,F). Prior to the removal of the compressive force, the excess solution surrounding the edges of the grids was blotted by filter paper, and then coated with a thin layer of vacuum grease to protect the aligned grids and its containing chamber.
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