Cherian Tomy, Sohrabi Fereshteh, Rigoni Carlo, Ikkala Olli, Timonen Jaakko V I
Department of Applied Physics, Aalto University School of Science, Puumiehenkuja 2, Espoo 02150, Finland.
Sci Adv. 2021 Dec 24;7(52):eabi8990. doi: 10.1126/sciadv.abi8990. Epub 2021 Dec 22.
It has been recognized that driving matter to nonequilibrium states can lead to emergent behaviors and functionalities. Here, we show that uniform colloidal dispersions can be driven into dissipative nonuniform states with emerging behaviors. We experimentally demonstrate this with electrically driven weakly charged superparamagnetic iron oxide nanoparticles in a nonpolar solvent. The driving leads to formation of nonequilibrium concentration gradients that further translate to nonequilibrium magnetism, including voltage-controlled magnetization and susceptibility. The concentration gradients also serve as diffuse interfaces that respond to external magnetic fields, leading to novel dissipative patterns. We identify the closest nondissipative analogs, discuss the differences, and highlight the ability to directly quantify the dissipation and link it to the pattern formation. Beyond voltage-controlled magnetism, we foresee that the concept can be generalized to other functional colloids to create, e.g., optical, electrical, catalytic, and mechanical responses that are not possible in thermodynamic equilibrium.
人们已经认识到，将物质驱动到非平衡态会导致涌现行为和功能。在此，我们表明均匀的胶体分散体可以被驱动到具有涌现行为的耗散非均匀态。我们通过在非极性溶剂中电驱动弱带电的超顺磁性氧化铁纳米颗粒进行了实验验证。这种驱动导致形成非平衡浓度梯度，进而转化为非平衡磁性，包括电压控制的磁化和磁化率。浓度梯度还充当对外部磁场作出响应的扩散界面，从而产生新颖的耗散模式。我们确定了最接近的非耗散类似物，讨论了差异，并强调了直接量化耗散并将其与图案形成联系起来的能力。除了电压控制的磁性之外，我们预计该概念可以推广到其他功能性胶体，以产生例如在热力学平衡中不可能实现的光学、电学、催化和机械响应。
