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

受经典老电影《神奇之旅》和最近的电影《内太空》的启发，许多科学家和工程师研究和开发了医用微游泳器，这些微游泳器可能在人体内部航行，用于药物输送、生物传感、成像、显微手术等难以到达的地方。到目前为止，已经开发了几种微游泳的方法，包括磁驱动、细菌利用、生物化学/生物燃料的使用等。然而，这些方法存在体积大、成本高、与人体不相容等缺点。此外，上述所有方法从未或很少与反馈控制或跟踪系统集成，以在三维空间中操纵微游泳者。该国家机器人计划（NRI）奖支持制造三维可操作、可生物降解、无系绳、微型游泳无人机的基础研究，研究/开发反馈控制算法来控制其三维轨迹，并在生物环境中对其进行评估。所提出的微型无人机是由声激发的微气泡推动的，这样它的驱动系统可以与目前的临床超声系统集成，修改最少。拟议的无人机对各种潜在的医疗应用具有巨大的社会效益影响：肿瘤的局部治疗，血管壁上脂肪沉积物的清除，血液凝块的破裂或清除，肾结石，肝结石，痛风，烧伤清洁和伤口清创，寄生虫的攻击和清除，肺部焦油的清除和破裂，药物输送和控制释放等。这项研究计划亦会对教育产生重大影响，包括：(i)为本科生和研究生重新设计跨/多学科领域的课程；（ii）让毕业生和本科生参与研究，特别是来自代表性不足群体的研究；（iii）在K-12学校和公共网站上展示该项目的成果，并为代表性不足的高中生举办机器人研讨会。最后，本研究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。3d微型游泳无人机将由可生物降解材料制成。无人机的气泡被外部施加的超声波振荡。聚焦或非聚焦激发的波允许单个无人机在三维空间中机动。基于动态逆的反馈控制器和状态观测器将控制激励美波的频率和幅度，以迫使无人机遵循/跟踪用户定义的3d路径。开发的无人机集成了驱动和控制单元，将在类似活体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，3d制造的基础物理、气泡/流体动力学、超声波波束成形方法和基于Lyapunov稳定性的反馈控制器估计器配置也将被研究。此外，还将提供控制的稳定性和收敛性保证。三维结构的制造和装配技术可以很容易地应用于许多领域，否则只能应用于二维结构。为美国微型物体的驱动/成像而开发的新型波束成形技术可以适用于更广泛、更普遍的高质量超声成像。对非线性（气泡）腔振荡和相关流体动力学的理解和新发现将有助于开发微血管结构内微气泡的最佳成像策略。此外，具有状态估计器的基于Lyapunov稳定性的非线性控制设计方法可以应用于只有部分信息可用的其他机器人（以及其他零动态非线性系统）的控制。研究成果将通过学术/工业会议和出版物传播，并与多/跨学科教育和公共宣传计划相结合。

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.