Mori Kurumi, Watanabe Takaichi, Ono Tsutomu
Department of Applied Chemistry, Graduate School of Environmental, Life, Natural Science and Technology, Okayama University, 3-1-1, Tsushima-naka, Kita-ku, Okayama 700-8530, Japan.
Langmuir. 2024 Dec 31;40(52):27314-27322. doi: 10.1021/acs.langmuir.4c03430. Epub 2024 Dec 18.
Nonspherical particles have gained significant interest owing to their unique shapes and large specific surface areas, making them suitable for a wide range of applications, such as drug delivery, catalysis, and adsorption. However, conventional methods for preparing nonspherical particles face certain limitations. In this study, we propose a simple method for fabricating nonspherical cellulose acetate (CA) microparticles using a microfluidic device in which droplets undergo rapid diffusion in a continuous aqueous phase. The influence of variations in the flow rate ratio and continuous phase composition on the dimensionless Péclet number () within the droplet and shape of the resultant particles is investigated. is critical, because it indicates the balance between polymer diffusion and droplet shrinkage dynamics. Our findings reveal that increasing the flow rate ratio and reducing the methyl acetate concentration in the continuous phase lead to faster droplet shrinkage and an increased . A high (>100) suggests that the reduction of the droplet interface predominates over polymer diffusion, resulting in the formation of a viscous layer near the droplet surface, which subsequently leads to nonspherical particle shapes (such as bowl-like or biconcave structures). In situ time-lapse observations of droplets from the top and side of a microchannel reveal that the formation of a viscous layer near the droplet surface and the deformation of the droplet, influenced by the -axis location of the droplets during particle formation, ultimately determine the final particle shape. Based on these observations, a linear correlation between the initial conditions, i.e., the and -axis location at which the viscous layer formed, is established, enabling the prediction of the particle structure. In summary, the present study enhances the understanding of shape control in microfluidic particle formation and offers a novel guideline for the fabrication of spherical and nonspherical particles.
非球形颗粒因其独特的形状和较大的比表面积而备受关注，使其适用于广泛的应用领域，如药物递送、催化和吸附。然而，传统的制备非球形颗粒的方法存在一定的局限性。在本研究中，我们提出了一种使用微流控装置制备非球形醋酸纤维素（CA）微粒的简单方法，其中液滴在连续水相中经历快速扩散。研究了流速比和连续相组成的变化对液滴内无量纲佩克莱数（）以及所得颗粒形状的影响。是至关重要的，因为它表明了聚合物扩散和液滴收缩动力学之间的平衡。我们的研究结果表明，增加流速比和降低连续相中的醋酸甲酯浓度会导致液滴更快收缩和增加。高（>100）表明液滴界面的减少超过了聚合物扩散，导致在液滴表面附近形成粘性层，随后导致非球形颗粒形状（如碗状或双凹结构）。从微通道顶部和侧面进行的液滴原位延时观察表明，液滴表面附近粘性层的形成以及液滴的变形，受颗粒形成过程中液滴轴位置的影响，最终决定了最终颗粒的形状。基于这些观察结果，建立了初始条件之间的线性相关性，即粘性层形成时的和轴位置，从而能够预测颗粒结构。总之，本研究增进了对微流控颗粒形成中形状控制的理解，并为球形和非球形颗粒的制造提供了新的指导方针。
