Electric-Field-Induced Lock-and-Key Interactions between Colloidal Spheres and Bowls

To
realize new and directed self-assembly (SA) pathways, the focus
in colloid science and nanoscience has shifted from spherical particles
and interactions to increasingly more complex shapes and interparticle
potentials. This field is fueled by recent breakthroughs in particle
synthesis, such as particles with complementary shapes that allow
for specific lock-and-key interactions induced by depletants. Here,
we show that electric fields form an alternative route for directing
the SA of convex and concave colloids, with the additional advantage
that the system now becomes switchable by external conditions. Both
experimental and theoretical results are presented that validate the
electric-field-induced assembly mechanism and show that even irreversibly
bound composites can be generated by tuning the force balance. The
successful isolation of the irreversible composite particles, in combination
with generalization to different materials, shows that the current
mechanism provides a versatile new path not only toward complex-particle
synthesis but also toward directed self-assembly.

为实现新型定向自组装（self-assembly, SA）路径，胶体科学与纳米科学领域的研究重心已从球形颗粒及其相互作用，转向愈发复杂的颗粒形状与粒子间势能。该领域的发展得益于颗粒合成技术的近期突破，例如具备互补形状的颗粒可通过排空剂（depletants）诱导产生特异性锁钥相互作用。本研究表明，电场为调控凸形与凹形胶体的自组装提供了一条全新途径，其额外优势在于该体系可通过外部条件实现动态调控。文中同时展示了验证电场诱导组装机制的实验与理论结果，并证实通过调控力平衡，甚至可制备得到不可逆结合的复合结构。成功分离不可逆结合的复合颗粒，并将该机制推广至不同材料体系，证明当前提出的机制不仅为复杂颗粒合成提供了通用新路径，也为定向自组装研究开辟了全新方向。