CAREER: Manufacturing Tools for the Next Generation of Tissue Engineering, Manufacturing Education for the Next Generation of Engineers

现在，人们可以想象通过使用机器人内窥镜3D打印机进行“钥匙孔”手术来制造人体内的工程化组织。这一长期愿景对医疗保健具有广泛的影响；外科医生替换患病和受损组织的方式可能会永远改变。该学院早期职业发展(CALEAR)奖支持一项关于内窥镜3D打印机中材料输送动力学的研究，这是实现这一愿景的必要步骤。该奖项还支持一项针对高中生的创新计划，为有特定行走障碍的患者设计一种辅助设备。内窥镜3D打印机由杆状末端效应器(用于将流体相材料通过手术部位输送)和运动学元件链(用于定位末端效应器)组成。有了这种外形因素，内窥镜3D打印机将在末端执行器的定位和材料输送子系统之间具有动态耦合(在标准3D打印机中观察不到)，并且在材料输送子系统中具有比标准3D打印机更高的流体阻力。第一个研究目标是建立末端执行器的解析输入-输出关系，并将输出值与计算模型进行比较。为了实现这一目标，将使用所建立的非牛顿胶体流体的Herschel-Bulkley本构模型来描述材料，同时将施加与内窥镜3D打印机末端执行器相关的几何约束和边界条件。将从输入-输出关系预测的输出(流量)与从多物理计算模型预测的输出值进行比较。第二个目标是测试两自由度材料输送执行器(旨在缓解较高的流体阻力)的输出上升时间将显著低于标称材料输送执行器的输出上升时间的假设。这一假设将通过实验得到检验。两种不同材料输送执行器的输出上升时间将在动态流量参考下由机器视觉测量。第三个目标是建立完整的内窥镜3D打印机的输入输出关系，并将输出值与实验进行比较。为了实现这一目标，将使用准静态运动学模型来描述运动学元素的串联链，然后将其与目标1和目标2中建立的末端执行器输入输出关系相耦合。来自输入-输出关系的多个输出预测(六个位置和一个流量)将与在原型内窥镜3D打印机上执行的实验的测量值进行比较。

It is now conceivable to fabricate engineered tissues inside the human body through a "keyhole" surgery with a robotic, endoscopic 3D printer. This long-term vision has broad implications for healthcare; the way in which surgeons replace diseased and damaged tissue could be forever transformed. This Faculty Early Career Development (CAREER) award supports a study on the dynamics of material delivery in an endoscopic 3D printer, a necessary step to realize this vision. This award also supports an innovative program for high school students to design an assistive device for patients with a specific ambulation disability. An endoscopic 3D printer is composed of a rod-like end-effector (to deliver a fluid-phase material through a "keyhole" surgical site) and a chain of kinematic elements (to position this end-effector). With this form-factor, an endoscopic 3D printer will have dynamic coupling between the positioning and material delivery sub-systems of the end-effector (not observed in a standard 3D printer), and a higher fluidic resistance in the material delivery sub-system than a standard 3D printer. The first research objective is to establish the analytic input-output relationship for the end-effector and compare the output value to a computational model. To achieve this objective, the established Herschel-Bulkley constitutive model for non-Newtonian colloidal fluids will be used to describe the material while geometric constraints and boundary conditions relevant to an endoscopic 3D printer end-effector will be imposed. The output (flowrate) prediction from the input-output relationship will be compared to the predicted output value from a multi-physics computational model. The second objective is to test the hypothesis that the output rise time of a two-degree-of-freedom material delivery actuator (designed to mitigate the higher fluidic resistance) will be significantly lower than the output rise time of a nominal material delivery actuator. This hypothesis will be tested by experiments. The output rise time for the two different material delivery actuators will be measured by machine vision under dynamic flowrate references. The third objective is to establish the input-output relationships of the complete endoscopic 3D printer and compare outputs values to an experiment. To achieve this objective, a quasi-static kinematic model will be used to describe the serial chain of kinematic elements, which will then be coupled with the end-effector input-output relationship established in objectives one and two. Multiple output predictions (six positions and one flowrate) from the input-output relationships will be compared to measured values from experiments performed on a prototype endoscopic 3D printer.