Flow profiles are frequently engineered in microfluidic channels for enhanced mixing, reaction control, and material synthesis. Conventionally, flow profiles are engineered by inducing inertial secondary flow to redistribute the streams, which can hardly be reproduced in microfluidic environments with negligible inertial flow. The employed symmetric channel structures also limit the variety of achievable flow profiles. Moreover, each of the flow profiles specifically corresponds to a strictly defined flow condition and cannot be generalized to other flow environments. To address these issues, we present a systematic method to engineer the flow profile using inertialess secondary flow. The flow is manipulated in the Stokes regime by deploying a cascaded series of microsteps with various morphologies inside a microchannel to shape the flow profile. By tuning the shapes of the microsteps, arbitrary outflow profiles can be customized. A numerical profile-transformation program is developed for rapid prediction of the output profiles of arbitrary sequences of predefined microsteps. The proposed method allows the engineering of stable flow profiles, including asymmetric ones, over a wide range of flow conditions for complex microfluidic environmental prediction and design.

流动剖面通常在微流体通道中设计，以增强混合、反应控制和材料合成。传统上，流动剖面是通过诱导惯性二次流来重新分配流来设计的，这在惯性流可忽略不计的微流体环境中很难重现。所采用的对称通道结构也限制了可实现的流动剖面的多样性。此外，每个流动剖面具体对应于严格定义的流动条件，不能推广到其他流动环境。为了解决这些问题，我们提出了一种使用无惯性二次流设计流动剖面的系统方法。通过在微通道内部署一系列具有各种形态的级联微步来塑造流动剖面，从而在斯托克斯体系中操纵流动。通过调整微步的形状，可以定制任意的流出曲线。开发了一个数值轮廓转换程序，用于快速预测预定义微步的任意序列的输出轮廓。所提出的方法允许在广泛的流动条件下设计稳定的流动剖面，包括不对称的流动剖面，用于复杂的微流体环境预测和设计。