In nonphotochemical laser-induced nucleation (NPLIN), an unfocused nanosecond laser pulse with low intensity (≈MW/cm²) triggers nearly instantaneous nucleation in supersaturated solutions, a process that would typically take days or weeks when the solution is left undisturbed. Previous studies have shown that the introduction of nanoparticles into supersaturated solutions enhances the probability of NPLIN measured during a fixed time window, compared to undoped control experiments. However, the precise mechanisms driving this enhancement remain unclear hampering industrial implementation of NPLIN. In this study, we systematically investigate how the properties of doped nanoparticles─specifically their concentration and chemical composition─affect the NPLIN probability in supersaturated urea solutions. We observed that higher laser intensities resulted in elevated NPLIN probabilities at a fixed pegylated gold nanoparticle (AuNP) concentration and supersaturation, while increasing concentrations of AuNPs at a fixed laser intensity and supersaturation interestingly led to higher NPLIN probabilities. Moreover, supersaturated solutions doped with gold nanoparticles exhibited significantly higher NPLIN probabilities compared to silica nanoparticle doped solutions at comparable nanoparticle size and concentration. We interpret these experimental results based on the impurity heating hypothesis as well as recent results highlighting the role of thermocavitation. We furthermore propose a helicopter-view model based on a thermodynamic equilibrium stage sequence. Our findings highlight the significance of nanoparticle properties in the design of heteronucleants optimized for NPLIN applications. ... Read more

We investigated the evaporative crystallization of aqueous glycine sessile droplets on hydrophilic glass, hydrophobic Teflon surfaces, and hydrophobic Teflon surfaces, where the contact angle is manipulated dynamically with electrowetting. Microscopy experiments and analytical characterization revealed that the size, morphology, and polymorphic form (α, β, and γ) of the glycine crystals are influenced by the surface wettability as well as the amplitude and frequency of electrowetting. On a hydrophilic glass surface, a coffee-stain-shaped residue composed of a mixture of bipyramidal α and needle-like β crystals was observed. On a hydrophobic Teflon surface, the droplets evaporated with minimum contact line pinning, producing hemispherical residue shapes, and bipyramidal α crystals smaller than 100 μm were formed. On a Teflon surface with electrowetting, glycine could be manipulated to crystallize into distinct polymorphic forms (β and γ) and residue shapes not observed on hydrophilic glass and hydrophobic Teflon surfaces. The frequency and amplitude of electrowetting were optimized to produce single large crystals. We observed the highest chance of producing single-millimeter-scale crystals at a frequency of 1 kHz and a voltage amplitude of 80 Vrms. We attribute this observation to a combination of nucleation at lower bulk supersaturation compared to the experiment on Teflon surfaces and electrowetting-induced mixing most prominent at 1 kHz. Our results highlight the opportunities arising from the dynamic manipulation of surface wettability ... Read more