基于溶胀原理的螺旋形微型机器人制备方法的研究

RESEARCH ON FABRICATION METHOD OF HELICAL MICROROBOTS BASED ON SWELLING EFFECT

汪子涵

11849224

硕士

机械电子工程

郑裕基

2020-06-03

2020-07-20

哈尔滨工业大学

深圳

螺旋形微型机器人在医学领域、细胞生物学和芯片实验室上有着巨大的应用潜力。在低雷诺数流体环境下，粘滞力将远远大于惯性力的作用，普通的往复式运动将不会引起位移（“扇贝”理论），这一结论是与直觉相悖的。受到自然界的启发，带有螺旋形鞭毛的细菌（如大肠杆菌）在该环境中展现出优越的游泳性能。因此，仿生螺旋形微型机器人的制备一直是近些年研究热点。本文提出了光刻-镀膜-湿法刻蚀三步法的制备方法，能高产量、低成本、可控化制备出螺旋形微型机器人。此外，进一步探索该制备方法中蕴含的实验原理，找到了光刻胶的溶胀作用导致了应力的产生，进而使得二维形状卷曲形成三维的螺旋形微结构。利用这一原理，通过改变二维模板的参数，对螺旋形微型机器人的几何形状实现了可控化制备。本论文采用旋转均匀磁场对螺旋形微型机器人进行了游泳性能表征，验证了运动速度与螺旋形微型机器人半径和体长的关系，运动速度与频率之间的线性关系，这些都是与目前已有的理论结果是相吻合的。在文末，还提出了反馈控制策略实现了螺旋形微型机器人沿着预定轨迹运动的控制。本文通过对螺旋形微型机器人制备方法和运动性能的研究，得到如下结论：第一，基于矩形模板的溶胀是各向同性的过程，因此卷曲方向不可控；而基于平行四边形模板的溶胀是各向异性的过程，卷曲方向将沿着垂直于短边方向；第二，以平行四边形模板制备螺旋形微型机器人，制备所得机器人的螺旋角约等于平行四边的倾斜角，螺旋形微型机器人的匝数也与模板长度成正比；第三，在测速过程中，螺旋形微型机器人游泳姿态受到外部磁场强度的影响。在保证游泳姿态相同的情况下，速度与频率之间的线性度更好。第四，利用反馈控制策略较为精准地实现了微型机器人的自主控制。本论文主要研究了螺旋形微型机器人的制备和控制两大方面。在制备方法上，简化了目前已有的制备方法，高效且低成本地实现了螺旋形微型机器人的量产。众所周知，在人体内如靶向送药的医疗任务中需要大量的微型机器人进行共同操作完成。因此，该制备方法的提出将为未来的医疗任务提供了原材料。随着反馈控制策略进一步的被验证，这也说明了螺旋形微型机器人能在未来的靶向治疗中实现精确治疗，让医疗微型机器人朝着产业化更进一步。

Helical microrobots have the potential to be used in a variety of application areas, such as in medical procedure, cell biology, or lab-on-a-chip. Reciprocal motion at low Reynold number, where viscous force dominates inertial force, will result in no net displacement; this is known as “scallop theorem”. This constraint led non-intuitive designs for microrobots that can generate nonreciprocal motion. Inspired by nature, the helical microrobots model after the bacteria with helical flagella, such as E. coli, and exhibit excellent swimming ability at low Reynold number. In recent years, the fabrication and control of artificial helical microrobots has become prominent subject in the field of micro-robotics.This work introduces a novel three-step rolled-up fabrication method. The three steps consist, in order, of photolithography, film deposition, and wet etching, this method is low-cost and high-throughput and relatively simple compared to existing preparation methods. After photoresist and a thin metal film are created via photolithography and film deposition sequentially and respectively, wet etching is used to release the photoresist. Simultaneously, the photoresist swells when reacting with the etchant; this leads to the formation of internal stress, resulting in the initially 2D patterns to self-scroll into strain-induced helical structures. The parameters of the fabrication process is highly controllable that allow for fine tuning of geometrical parameters of the helical microrobots. For instance, the geometry of helical microrobots could be tuned by controlling the dimensions of the 2D patterns. The effects of the microrobots’ helical parameters to their swimming properties characterized under rotational magnetic fields of various frequencies; a linear relationship was observed between swimming velocity and the length and radius of helical microrobots. The above conclusions correspond with existent theorems. Finally, a feedback control strategy was implemented to control helical microrobots to move along the pre-programmed trajectories.After studying the fabrication method and swimming ability of helical microrobots, four major observations were listed below. First, the direction of scrolling can be controlled using parallelogram templates; this is because self-scrolling of parallelogram templates is anisotropic while self-scrolling of rectangular templates is isotropic. Second, the helical angle and the number of turns of the helical microrobots were approximately equal to the tilt angle of parallelogram template and proportional to the length of template, respectively. Third, a linear relationship between velocity and frequency was observed only if the angle between the rotation axis and the helical axis (wobbling angle) is constant. Last but not least, the motion of helical microrobots can be controlled with microscale precision using feedback control strategy. Based on these observations, it was demonstrated that this work yields a way to massively fabricate helical microrobots with tunable geometrical properties and controllable motion. The results have important implications to medical procedures that must be performed using a large amount of microrobots, such as drug delivery. Furthermore, the feedback control of the microrobots serves as proof-of-concept for where motion control with high precision is necessary, such as targeted therapy. With a deeper understanding of their fabrication and control, medical microrobots will be able to slowly but surely move towards industrialization.

医疗微型机器人 螺旋形微型机器人 低成本 高产量 反馈控制

medical microrobots helical microrobots low cost mass production feedback control

中文

联合培养

南方科技大学

汪子涵. 基于溶胀原理的螺旋形微型机器人制备方法的研究[D]. 深圳. 哈尔滨工业大学,2020.