Priyadarshani Jyotsana, Awasthi Prasoon, Das Soumen, Chakraborty Suman
School of Medical Science & Technology, Indian Institute of Technology Kharagpur, Kharagpur 721302, India; Department of Mechanical Engineering, KU Leuven, Leuven 3001, Belgium.
School of Medical Science & Technology, Indian Institute of Technology Kharagpur, Kharagpur 721302, India.
J Colloid Interface Sci. 2023 Jun 15;640:246-260. doi: 10.1016/j.jcis.2023.02.089. Epub 2023 Feb 18.
A liquid filament may pinch off into different shapes on interacting with a soft surface, as modulated by the interplay of inertial, capillary, and viscous forces. While similar shape transitions may intuitively be realized for more complex materials such as soft gel filaments as well, their intricate controllability towards deriving precise and stable morphological features remains challenging, as attributed to the complexities stemming from the underlying interfacial interactions over the relevant length and time scales during the sol-gel transition process. Circumventing these deficits in the reported literature, here we report a new means of precisely-controlled fabrication of gel microbeads via exploiting thermally-modulated instabilities of a soft filament atop a hydrophobic substrate. Our experiments reveal that abrupt morphological transitions of the gel material set in at a threshold temperature, resulting in spontaneous capillary thinning and filament breakup. We show that this phenomenon may be precisely modulated by an alteration in the hydration state of the gel material that may be preferentially dictated by its intrinsic glycerol content. Our results demonstrate that the consequent morphological transitions give rise to topologically-selective microbeads as an exclusive signature of the interfacial interactions of the gel material with the deformable hydrophobic interface underneath. Thus, intricate control may be imposed on the spatio-temporal evolution of the deforming gel, facilitating the inception of highly ordered structures of specific shapes and dimensionalities on demand. This is likely to advance the strategies of long shelf-life analytical biomaterial encapsulations via realizing one-step physical immobilization of bio-analytes on the bead surfaces as a new route to controlled materials processing, without demanding any resourced microfabrication facility or delicate consumable materials.
液丝在与柔软表面相互作用时，可能会因惯性、毛细管力和粘性力的相互作用而捏断成不同形状。虽然对于更复杂的材料，如软凝胶丝，直观上也可能实现类似的形状转变，但由于在溶胶-凝胶转变过程中，相关长度和时间尺度上的潜在界面相互作用所带来的复杂性，要实现对其精确和稳定形态特征的复杂可控性仍然具有挑战性。为了克服现有文献中的这些不足，我们在此报告一种通过利用疏水基底上软丝的热调制不稳定性来精确控制凝胶微珠制造的新方法。我们的实验表明，凝胶材料在阈值温度下会发生突然的形态转变，导致自发的毛细管变细和丝断裂。我们表明，这种现象可以通过改变凝胶材料的水合状态来精确调节，而凝胶材料的水合状态可能优先由其固有甘油含量决定。我们的结果表明，随之而来的形态转变会产生拓扑选择性微珠，这是凝胶材料与下方可变形疏水界面之间界面相互作用的独特标志。因此，可以对变形凝胶的时空演化进行复杂控制，从而便于按需产生具有特定形状和尺寸的高度有序结构。这可能会推进长保质期分析生物材料封装的策略，通过在珠子表面实现生物分析物的一步物理固定，作为一种可控材料加工的新途径，而无需任何资源丰富的微制造设备或精细的消耗性材料。
