Schematic illustration of the proposed microfluidic chip designs and the employed experimental setup for successively learning and testing practices of zebrafish larvae.

Microrobots have been developed and extensively employed for performing the variety tasks with various applications. However, the intricate fabrication and actuation processes employed for microrobots further restrict their multitudinous applicability as well as the controllability in high accuracy. As an alternative, in this work an aquatic microrobot was developed using a distinctive concept of the building block technique where the microrobot was built based on the block to block design. An in-house electromagnetic system as well as the control algorithm were developed to achieve the precise real-time dynamics of the microrobot for extensive applications. In addition, pivotal control parameters of the microrobot including the actuating waveforms together with the operational parameters were verified and discussed in conjunction with the magnetic intensity simulation. A mixing task was performed with high efficiency based on the trajectory planning and rotation control of the microrobot to demonstrate its capability in flow manipulation which can be advantageous for microreactor applications down the load. Aside from it, a dissolution test was further conducted to provide an on-demand flow agitation function of the microrobot for the next level of lab chip applications. The presented work with detail dynamic analysis is envisaged to provide a new look of microrobot control and functions from the engineering perspective with profoundly potential applications.

Artificial cilia are widely employed in microfluidic platforms, where their beating motion is harnessed to emulate the fluid transport capabilities of natural motile cilia. In particular, metachronal beating, characterized by phase-shifted motion among adjacent cilia, has proven to be effective for directional fluid transport. However, its potential for micromixing remains limited due to its inherently planar wave propagation, which offers room for improvement in generating strong vortices. To address this, three magnetically actuated artificial cilia carpets are fabricated with identical structural designs featuring spatially varied cilia orientations to embed controlled orientational asymmetry. To realize distinct motion patterns, each carpet is magnetized with a single, unique magnetization profile such that one carpet corresponds to one beating mode, including synchronous, symplectic metachronal, or antiplectic metachronal, and is actuated externally to generate its respective motion. For demonstration purposes, two different experiments are conducted, including micromixing and photocatalytic dye degradation. The results reveal that metachronal motion alone is insufficient to enhance micromixing, thereby highlighting the need for integration with orientational asymmetry. Compared to the aligned cilia carpet (control), superior mixing efficiency of 87% and a 3-fold enhancement in dye degradation are observed in the inclined cilia carpet actuated with antiplectic metachronal motion. This enhanced hydrodynamic activity is further substantiated through μPIV experiments. These findings define metachrony as a dual-function paradigm for both fluid propulsion and vortex-enabled microfluidic mixing.