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of superwetting surfaces. [3,4] Up to now, many methods have been developed to produce superhydrophobic surface via creating rough structures or attaching small particles on the surface through various strategies. [5][6][7] Nowadays, transition metals cobalt (Co) and nickel (Ni) and their bimetallic alloys are of great interest on account of their unique and desirable properties, such as high values of saturation magnetization (M s ), excellent mechanical strength, and facile synthesis routes. [8,9] The CoNi alloys have been used in many fields, such as catalysis, microwave absorption, biomedical devices, and magnetic resonance imaging. [10][11][12] In general, the applications of CoNi alloys depend on two factors: chemical composition and morphology, which determine their intrinsic magnetic moment, magnetic permeability, and wettability. In general, Co-rich CoNi alloys possess high values of M s . Stimuli control of magnetic particles is a challenge for basic research, whereas it is a promising way for advanced applications. In contrast to conventional carbonyl iron particles, Co, Ni, and their bimetallic alloys provide a viable alternative for magnetorheological (MR) materials owning to their high values of M s and good controllability for their morphology.MR fluids are a kind of intelligent materials, which usually consist of micrometer-sized magnetizable particles dispersed in a liquid media. [13][14][15] When exposed to an external magnetic field, the dispersed particles get magnetized and develop magnetic moments, which give rise to strong magnetostatic attraction between adjacent particles and consequently build up aligned fiber-like structures. [15,16] The resulting field-induced structures hinder the free flow of the former Newtonian fluid, and high values of the yield stress and viscosity are observed, which is called MR effect. [17] Applications based on MR fluids, such as couplings, actuators, clutches, and vibration dampers, employ the shearing and squeezing strength of MR fluids. [18][19][20] The hottest topics on MR fluids are finding ways to improve their yield stress, stability upon settling, and activity over a wide temperature range. Current fundamental research on MR fluids mainly focuses on the alleviation of settling issues for MR suspensions, which may restrict their use in practical applications. To achieve this goal, several promising strategies Designing and fabricating a rational surface architecture is one of the critical factors to achieve desirable physical and chemical properties and still remains an immense challenge. Herein, a series of CoNi-based hierarchical microspheres with different surface morphologies, including litchi-like, seed-of-plane-tree-like, and waxberry-like shapes, are obtained via surface nucleation of carbon quantum dots (CQDs) with different concentrations in liquid polyol. Microstructure investigations suggest that all the CoNi microspheres are uniformly with enhanced surface roughness with the increasing concentration of CQDs. This study provides insight into...

A series of CoNi based hierarchical microspheres with different surface morphologies, including litchi‐like, seed of plane tree‐like and waxberry‐like shapes, are obtained via surface nucleation of carbon quantum dots (CQDs). Taking both the synergistic benefits of paramagnetic CoNi microspheres and surface architecture, the resulting CoNi microspheres exhibit enhanced interparticle friction for enhancing their MR effects compared with smooth surface microspheres. This work is reported by Wen Ling Zhang, Jingquan Liu and co‐workers in article number https://doi.org/10.1002/admi.201800164.