(654b) Micro-Droplet Evaporative Crystallization on 3D Printed Platform for Particle Screening

Droplet evaporative crystallization on microscale heterogeneous surface is a vivid topic in chemical engineering, bioengineering, nanomaterials, etc.

Here, 3D printed interfacial matrix platform with regular pillar convexity and tunnel structure is fabricated to reveal the mechanism of the interfacial micro droplet crystallization. The nucleus generation and crystal migration governed by confined capillary flow the inside micro-size liquid drop was investigated, which highlighted the dynamic concentration distribution of crystallization solution and ternary phase interface contact angle as essential variables. In addition, element-based rotation volume (EBRV) model is established to simulate the concentration and nucleation barrier distribution during the microscale process. The developed EBRV model accompanied by the in-situ image detective method can simulate the nonuniformed concentration distribution varying with time and the liquid drop position.

The pillar convex structure with limited area on the research platform could allow to choose the initial contact angle to enlarge the space of confined capillary flow and ascent the nucleation barrier before evaporation. In addition, the various concentrations of crystallization solution can influence the nucleation barrier, the subsequent crystal growth and flow governing particle migration. Therefore, the interior flow field and nucleation energy barrier distribution can be established benefited from the known concentration distribution during droplet evaporation. The droplet crystallization over the tunnel structure exhibited the additional function of the two specific regions that can isolated obtain the crystal particles from nanoscale to even millimetre scale.

To sum up, an interesting alternative approach on multiple scale crystals preparation and screen in this respect can be developed. All the results and conclusion were of paramount importance to uncover the fundamental theory and novel approach development for the accurate control and screen solid products in the micro-scale limited space.

Figure 1 (A) The classic droplet contact angle at different evaporative stages; (B) terminal nucleation density and average crystal size of SUM and NaCl droplets on the on the pillar convex; Crystal formation route of SUM droplet (C) and NaCl droplet (D) on the pillar convex and PAA flat sheet.

Acknowledgment

We acknowledge the financial contribution from National Natural Science Foundation of China (No. 21527812, 21676043, U1663223, 21978037), MOST innovation team in key area (No. 2016RA4053) and Fundamental Research Funds for the Central Universities (DUT19TD33).