Time‐Resolved Dynamics of Struvite Crystallization: Insights from the Macroscopic to Molecular Scale

Abstract

The crystallization of magnesium ammonium phosphate hexahydrate (struvite) often occurs under conditions of fluid flow, yet the dynamics of struvite growth under these relevant environments has not been previously reported. In this study, we use a microfluidic device to evaluate the anisotropic growth of struvite crystals at variable flow rates and solution supersaturation. We show that bulk crystallization under quiescent conditions yields irreproducible data owing to the propensity of struvite to adopt defects in its crystal lattice, as well as fluctuations in pH that markedly impact crystal growth rates. Studies in microfluidic channels allow for time‐resolved analysis of seeded growth along all three principle crystallographic directions and under highly controlled environments. After having first identified flow rates that differentiate diffusion and reaction limited growth regimes, we operated solely in the latter regime to extract the kinetic rates of struvite growth along the [100], [010], and [001] directions. In situ atomic force microscopy was used to obtain molecular level details of surface growth mechanisms. Our findings reveal a classical pathway of crystallization by monomer addition with the expected transition from growth by screw dislocations at low supersaturation to that of two‐dimensional layer generation and spreading at high supersaturation. Collectively, these studies present a platform for assessing struvite crystallization under flow conditions and demonstrate how this approach is superior to measurements under quiescent conditions.

Engaging a Battle on Two Fronts: Dual Role of Polyphosphates as Potent Inhibitors of Struvite Nucleation and Crystal Growth

“…We recently used in situ AFM to establish that struvite crystal growth follows a classical mechanism, whereby new layers nucleate on crystal surfaces and advance by the incorporation of solute molecules at steps. 50 Indeed, a snapshot of a (101) surface during growth in a supersaturated solution (Figure 6A)…”

“…AFM has proven to be a powerful technique for characterizing the growth of crystal surfaces in the absence and presence of inhibitors. We recently used in situ AFM to establish that struvite crystal growth follows a classical mechanism whereby new layers nucleate on crystal surfaces and advance by the incorporation of solute molecules at steps 50 . Indeed, a snapshot of a (101) surface during growth in supersaturated solution (Figure 6A) shows the presence of layers emanating from the bottom left (outside the frame of imaging) with heights equivalent to a single unit cell (h = 0.58 nm).…”

“…A microfluidics device was used to examine struvite growth at macroscopic length scale. The device (poly­(dimethylsiloxane) (PDMS) on glass) used for these experiments followed the same set up and fabrication protocol as reported in previous work. , This system was monitored under continuous supply of a growth solution using a semiautomatic inverted light microscope (Leica DMi8 equipped with PL Fluotar 5×, 10×, 20×, and N Plan L 50× objectives).…”

Fluid mechanical modeling of the upper urinary tract

“…Such studies, together with recent advances in 4D printing (Sydney Gladman et al, 2016), may enable optimization of the design of ureteral stents by prescribing desired properties. Meanwhile, several studies in microbiology have shown the influence of fluid mechanical characteristics on microbial behavior (Kim, Olympiou, McCoy, Irwin, & Rimer, 2020; Laffite et al, 2016; Salta et al, 2013; Zalewska‐Piatek et al, 2020) especially the correlation between the micro‐scale shear stress field and the mobility or attachment of bacteria (Rusconi & Stocker, 2015; Sherman et al, 2019). These efforts will open new avenues to the study of urinary flows, leading to novel ideas and solutions for various urological symptoms, ultimately contributing to the well‐being of individual patients.…”

Suppressing Barium Sulfate Crystallization with Hydroxycitrate: A Dual Nucleation and Growth Inhibitor

“…Crystallization is a ubiquitous phenomenon in natural, biological, and synthetic processes that poses significant problems for pathological or infectious human diseases − and scale formation in industrial pipelines − and wellbores . Research efforts to curtail the deleterious effects of mineral precipitation are focused on the development of economical, facile routes to inhibit crystallization.…”