The Interrelationship Between Friction and Fracture in Needle Insertion

该奖项将促进对针头插入基本力学的理解。尽管基于针头的医疗程序和大量的针头插入研究无处不在，但在理解方面存在重大差距。需要对穿刺后针插入过程中的滑动摩擦和材料断裂进行量化，以评价新的针设计及其可能插入的软材料。目前计算预测的缺点部分源于缺少对摩擦和断裂相互影响的描述。更详细的了解是至关重要的微创方法的成功扩展到身体表面以外的地区。成功地描述这些影响的基本机制将有助于控制方案，并使新的针设计的快速评估。这项研究预计最终会减少患者的不适感、愈合时间和手术成本。这项研究将与一个研究生研究小组一起实施，他们将接受管理培训，以协调本科学员的努力。研究人员将通过社交媒体分享他们的经验和发现，旨在为公众阐明材料力学研究的挑战，回报和过程。这项研究将量化穿刺后针头插入过程中滑动摩擦和材料断裂的同时和相互影响。最初的目标将引导工作首先了解断裂对表面形态的影响以及后者对摩擦的影响。一旦获得，这些单独的影响将统一在同时描述界面力学沿着针杆和针尖断裂的主要目标。试验将在准静态至试验相关速率下进行。首先，通过控制断裂可用能量（通过尖端半径和平面和针几何形状中的边界条件）和材料本构响应，使用两种典型的针插入研究的表征良好的材料系统，但具有不同的失效行为：油稀释硅树脂（更硬）和水凝胶（更脆），将系统地改变表面损伤形态。其次，表面损伤形态对滑动摩擦阻力的影响将被测量，以建立相关性和临界状态作为速率和法向力的函数。最后，使用这些相关性，将平面切割几何形状条件映射到圆柱形针头插入几何形状，以量化摩擦效应，摩擦效应将通过表面改性进一步调整。该标测将通过在原位针插入和切割期间从全场应变测量获得的局部失效标准启动。由此产生的摩擦和断裂之间的相互关系的基本理解将通知针插入的更强大的计算模型的发展，并导致更精细和改进的机器人针插入模型。这两项进展都将促进微创、组织特异性针头设计的发展。该奖项反映了NSF的法定使命，并且通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This award will advance understanding of the fundamental mechanics of needle insertion. Despite the ubiquity of needle-based medical procedures and a wealth of needle insertion studies, there are critical gaps in understanding. Quantification of the sliding friction and material fracture during post-puncture needle insertion is needed to evaluate new needle designs and the soft materials into which they may be inserted. The current shortcomings in computational prediction stem in part from a missing description of the effect of friction and fracture on one another. A more detailed understanding is critical to the successful expansion of minimally invasive methods to areas beyond the body’s surface. Successful description of the fundamental mechanics of these effects will both facilitate control schemes and enable rapid evaluation of novel needle designs. This research is expected to ultimately result in reduced patient discomfort, healing time, and procedure costs. This research will be implemented with a team of graduate researchers who will receive management training to coordinate the effort of undergraduate trainees. The researchers will share their experiences and findings via social media with the aim of illuminating the challenges, rewards, and process of mechanics of materials research for the public.This research will quantify the simultaneous and reciprocal effects of sliding friction and material rupture during post-puncture needle insertion. Initial goals will guide the work toward first understanding the influence of fracture on surface morphology and the latter’s influence on friction. Once gained, these separate effects will be unified in the primary goal of simultaneously describing interfacial mechanics along the needle shaft and fracture at the needle tip. Tests will be performed at quasi-static to surgically-relevant rates. First, surface damage morphology will be systematically varied by controlling both the energy available to fracture (via tip radius and boundary conditions in planar and needle geometries) and material constitutive response using two well-characterized materials systems typical of needle insertion studies, but having different failure behaviors: oil-diluted silicone (tougher) and hydrogel (more brittle). Second, the effect of surface damage morphology on frictional resistance to sliding will be measured to establish correlations and critical regimes as a function of rate and normal force. Finally, using these correlations, planar cutting geometry conditions will be mapped to the cylindrical needle-insertion geometry to quantify frictional effects which will be further tuned via surface modification. This mapping will be initiated via local failure criteria obtained from full field strain measurement during in situ needle insertion and cutting. The resulting fundamental understanding of the interrelationship between friction and fracture will inform the development of more robust computational models of needle insertion and lead to more refined and improved models for robotic needle insertion. Both advances will enhance the development of minimally-invasive, tissue-specific needle designs.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.