Kumat Shashank S, Shiakolas Panos S
Mechanical and Aerospace Engineering Department, The University of Texas at Arlington, S Nedderman Dr, Arlington, 76019, TX, USA.
3D Print Med. 2022 Jan 4;8(1):1. doi: 10.1186/s41205-021-00128-2.
Tissue healthiness could be assessed by evaluating its viscoelastic properties through localized contact reaction force measurements to obtain quantitative time history information. To evaluate these properties for hard to reach and confined areas of the human body, miniature force sensors with size constraints and appropriate load capabilities are needed. This research article reports on the design, fabrication, integration, characterization, and in vivo experimentation of a uniaxial miniature force sensor on a human forearm.
The strain gauge based sensor components were designed to meet dimensional constraints (diameter ≤3.5mm), safety factor (≥3) and performance specifications (maximum applied load, resolution, sensitivity, and accuracy). The sensing element was fabricated using traditional machining. Inverted vat photopolymerization technology was used to prototype complex components on a Form3 printer; micro-component orientation for fabrication challenges were overcome through experimentation. The sensor performance was characterized using dead weights and a LabVIEW based custom developed data acquisition system. The operational performance was evaluated by in vivo measurements on a human forearm; the relaxation data were used to calculate the Voigt model viscoelastic coefficient.
The three dimensional (3D) printed components exhibited good dimensional accuracy (maximum deviation of 183μm). The assembled sensor exhibited linear behavior (regression coefficient of R=0.999) and met desired performance specifications of 3.4 safety factor, 1.2N load capacity, 18mN resolution, and 3.13% accuracy. The in vivo experimentally obtained relaxation data were analyzed using the Voigt model yielding a viscoelastic coefficient τ=12.38sec and a curve-fit regression coefficient of R=0.992.
This research presented the successful design, use of 3D printing for component fabrication, integration, characterization, and analysis of initial in vivo collected measurements with excellent performance for a miniature force sensor for the assessment of tissue viscoelastic properties. Through this research certain limitations were identified, however the initial sensor performance was promising and encouraging to continue the work to improve the sensor. This micro-force sensor could be used to obtain tissue quantitative data to assess tissue healthiness for medical care over extended time periods.
通过局部接触反应力测量来评估组织的粘弹性特性，以获取定量的时间历程信息，从而评估组织的健康状况。为了评估人体难以触及和受限区域的这些特性，需要尺寸受限且具有适当负载能力的微型力传感器。本文报道了一种用于人体前臂的单轴微型力传感器的设计、制造、集成、表征及体内实验。
基于应变片的传感器组件设计需满足尺寸约束（直径≤3.5mm）、安全系数（≥3）和性能规格（最大施加负载、分辨率、灵敏度和精度）。传感元件采用传统加工制造。利用倒置桶光聚合技术在Form3打印机上制作复杂组件的原型；通过实验克服了制造过程中微组件定向的挑战。使用静重和基于LabVIEW定制开发的数据采集系统对传感器性能进行表征。通过在人体前臂上的体内测量来评估操作性能；利用松弛数据计算Voigt模型粘弹性系数。
三维（3D）打印组件具有良好的尺寸精度（最大偏差为183μm）。组装后的传感器呈现线性行为（回归系数R = 0.999），并满足所需的性能规格，安全系数为3.4，负载能力为1.2N，分辨率为18mN，精度为3.13%。使用Voigt模型对体内实验获得的松弛数据进行分析，得出粘弹性系数τ = 12.38秒，曲线拟合回归系数R = 0.992。
本研究成功设计了用于评估组织粘弹性特性的微型力传感器，并通过3D打印进行组件制造、集成、表征以及对初始体内收集测量数据的分析，性能优异。通过本研究发现了一些局限性，然而初始传感器性能令人鼓舞，有望继续改进传感器的工作。这种微力传感器可用于获取组织定量数据，以长期评估医疗护理中的组织健康状况。
