NRI: 3-D Maneuverable Feedback-Controlled Micro Swimming Drone for Biomedical Applications

受经典老电影《奇幻之旅》和最近的电影《内太空》的启发，许多科学家和工程师研究开发了医用微游器，这种游泳器可能在人体内导航，用于在难以到达的地点进行药物递送、生物传感、成像、显微手术等目的。到目前为止，已经开发出了几种微泳者的方法，包括磁力驱动、利用细菌、使用生物化学/生物燃料等，但这些方法都存在体积大、成本高、与人体不兼容等缺点。此外，所有上述方法从未或很少与反馈控制或跟踪系统相结合，以在三维空间中操纵微泳者。这一国家机器人计划(NRI)奖支持以下方面的基础研究：制造三维可机动、可生物降解、无绳索的微型游泳无人机，研究/开发反馈控制算法以控制其三维轨迹，并在生物环境中对其进行评估。拟议的微型无人机由声学激发的微气泡推动，因此其驱动系统可以与当前的临床超声系统集成，只需最小的修改。拟议中的无人机对各种潜在的医疗应用具有巨大的社会效益：局部治疗肿瘤，去除血管壁上的脂肪沉积，破裂或移除血栓，肾结石，肝结石，痛风，烧伤清理和伤口清创，攻击和清除寄生虫，去除和破坏肺部的焦油，药物输送和控制释放等。该研究项目还将通过以下方式对教育产生重大影响：(I)为跨学科/多学科领域的本科生和研究生重新设计课程；(Ii)让本科生和本科生参与研究，特别是来自代表性不足的群体；以及(Iii)在K-12学校和公共网站上展示这一项目的成果，并为代表性不足的高中生举办机器人研讨会。最后，这项研究中的实验设置的完成将改善匹兹堡大学科学和工程培训的基础设施。这架3D微型游泳无人机将由可生物降解材料制成。无人机上有气泡，由外部施加的超声波振荡。聚焦或非聚焦激发的波允许单独的无人机在3-D空间中进行机动。基于动态逆的反馈控制器和状态观测器将控制激励US波的频率和幅度，以迫使无人机遵循/跟踪用户定义的3-D路径。开发的无人机将与驱动和控制单元集成在一起，将在类似于生物器官的水动力条件下进行测试，以探索可能的实际应用。同时，还将研究3D制造的基本物理、气泡/流体动力学、超声波波束形成方法以及基于Lyapunov稳定性的反馈控制器-估计器配置。此外，还将提供控制的稳定性和收敛保证。三维结构的制造和组装技术可以很容易地应用于许多领域，否则这些领域的应用仍然停留在二维结构上。为微目标的超声驱动/成像开发的新的波束形成技术可以适用于更广泛的一般应用的高质量的超声成像。对非线性(气泡)腔振荡和相关流体动力学的理解和新发现的进展将有助于发展微血管结构内微泡的最佳成像策略。此外，带状态估值器的基于Lyapunov稳定性的非线性控制设计方法也可以应用于其他机器人(以及其他具有零动态的非线性系统)的控制。研究成果将通过学术/行业会议和出版物传播，并与多学科/跨学科教育和公共推广计划相结合。

Inspired by the old classic movie "Fantastic Voyage" and the relatively recent movie "Inner Space", many scientist and engineers have investigated and developed medical microswimmers that possibly navigate inside human body for the purpose of drug delivery, bio-sensing, imaging, micro surgery, etc. in the hard-to-reach spots. So far, several methods for microswimmers have been developed including magnetic actuation, harness of bacteria, use of biological chemical/biological fuels, etc. However, these methods have many drawbacks including high bulkiness, high cost and incompatibility with human body. In addition, all the above methods were never or rarely integrated with feedback control or tracing systems to maneuver the microswimmer in a three-dimensional space. This National Robotics Initiative (NRI) award supports fundamental research on manufacturing three-dimensionally maneuverable, biodegradable, untethered, micro swimming drones, studying/developing feedback control algorithms to control their three-dimensional trajectory, and evaluating them in biological environments. The proposed micro drone is propelled by acoustically excited micro bubbles such that its driving system can be integrated with the current clinical ultrasound system with minimal amendment. The proposed drone has tremendous impact with societal benefits on various potential medical applications: local treatments of tumors, removal of fatty deposits on blood vessel walls, break or removal of blood clots, kidney stones, liver stones, gouts, burn cleaning and wound debriding, attack and removal of parasites, removal and break of tar in lungs, drug delivery and controlled release, etc. This research project will also have significant impact on education by (i) re-engineering coursework for both undergraduates and graduates in inter/multi-disciplinary areas; (ii) having graduates and undergraduates involved in research especially from the underrepresented groups; and (iii) demonstrating results from this project in K-12 schools and in public websites and hosting a robotics workshop for underrepresented high school students. Finally, the completion of experimental setups in this research will improve infrastructure for training in science and engineering at University of Pittsburgh. The 3-D micro swimming drone will be microfabricated from biodegradable materials. The drone has gaseous bubbles being oscillated by externally applied ultrasound waves. The waves with focused or unfocused excitation allows individual drones to maneuver in a 3-D space. A dynamic inversion-based feedback controller and a state observer will control the frequency and amplitude of the exciting US waves to force the drone to follow/track a user-defined 3-D path. The developed drone integrated with actuation and control units will be tested under hydrodynamic conditions similar to living organs to explore possible practical applications. In parallel, the underlying physics of 3-D manufacturing, bubble/fluid dynamics, ultrasound beamforming method, and a Lyapunov stability based feedback controller-estimator configuration will be investigated. In addition, stability and convergence guarantees in control will be provided. The fabrication and assembly technique of 3-D structures can be readily applied to many fields whose applications otherwise remain on 2-D structures. Novel beamforming technologies developed for US actuating/imaging of micro object can be adapted for high quality ultrasound imaging for broader, general applications. Advances in understanding and new findings of nonlinear (bubble) cavity oscillation and associated fluid dynamics will help develop the best imaging strategy for microbubbles inside microvasculature structures. In addition, the Lyapunov stability-based nonlinear control design method with a state estimator can be applied to control other robots (and other nonlinear systems with zero dynamics) where only partial information is available. The research results will be disseminated through academic/industrial meetings and publications and integrated with multi-/inter-disciplinary education and public outreach programs.