Design, inverted vat photopolymerization 3D printing, and initial characterization of a miniature force sensor for localized in vivo tissue measurements.

BACKGROUND: 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. METHODS: 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. RESULTS: The three dimensional (3D) printed components exhibited good dimensional accuracy (maximum deviation of 183µm). The assembled sensor exhibited linear behavior (regression coefficient of R2=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 R2=0.992. CONCLUSIONS: 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.

An operator-independent artificial finger can differentiate anterior vaginal wall indentation parameters between control and prolapse patients.

In this study, the reproducibility and validity of an automated artificial finger for evaluating properties of vaginal wall tissue was assessed. The effect of angle and rate of indentation on displacing the anterior vaginal wall (AVW) was studied in control and prolapse patients. Following IRB approval, an automated artificial finger equipped with a calibrated piezoresistive sensor at its tip was used to induce 3-second AVW deformation sequences (10°, 15°, and 20° indentation). Measurements were taken in patients in supine position, either awake in clinic or under anesthesia in the operating room (OR). The real time voltage output of a sensor (linearly proportional to the reaction force) was recorded for each motion profile to calculate key parameters: baseline voltages, amplitude changes over indentation intervals, and slopes of indentation curves. 23 women (9 controls and 14 prolapse) were studied, 6 in clinic and 17 in OR. No differences in mean reproducibility was noted across groups. There was a significant difference in sensor output based on selected motion profile parameters between different degrees of indentation for all women (p < 0.001) and in baseline voltage between age-matched and non-age-matched controls (p < 0.02). From these findings, we can conclude that indentation reaction properties of prolapsed and non-prolapsed AVW can be objectively measured using an operator-independent artificial finger with significant differences between patient groups.

Building a Networked Improvement Community: Lessons in Organizing to Promote Diversity, Equity, and Inclusion in Science, Technology, Engineering, and Mathematics.

In 2016, 10 universities launched a Networked Improvement Community (NIC) aimed at increasing the number of scholars from Alliances for Graduate Education and the Professoriate (AGEP) populations entering science, technology, engineering, and mathematics (STEM) faculty careers. NICs bring together stakeholders focused on a common goal to accelerate innovation through structured, ongoing intervention development, implementation, and refinement. We theorized a NIC organizational structure would aid understandings of a complex problem in different contexts and accelerate opportunities to develop and improve interventions to address the problem. A distinctive feature of this NIC is its diverse institutional composition of public and private, predominantly white institutions, a historically Black university, a Hispanic-serving institution, and land grant institutions located across eight states and Washington, DC, United States. NIC members hold different positions within their institutions and have access to varied levers of change. Among the many lessons learned through this community case study, analyzing and addressing failed strategies is as equally important to a healthy NIC as is sharing learning from successful interventions. We initially relied on pre-existing relationships and assumptions about how we would work together, rather than making explicit how the NIC would develop, establish norms, understand common processes, and manage changing relationships. We had varied understandings of the depth of campus differences, sometimes resulting in frustrations about the disparate progress on goals. NIC structures require significant engagement with the group, often more intensive than traditional multi-institution organizational structures. They require time to develop and ongoing maintenance in order to advance the work. We continue to reevaluate our model for leadership, climate, diversity, conflict resolution, engagement, decision-making, roles, and data, leading to increased investment in the success of all NIC institutions. Our NIC has evolved from the traditional NIC model to become the Center for the Integration of Research, Teaching and Learning (CIRTL) AGEP NIC model with five key characteristics: (1) A well-specified aim, (2) An understanding of systems, including a variety of contexts and different organizations, (3) A culture and practice of shared leadership and inclusivity, (4) The use of data reflecting different institutional contexts, and (5) The ability to accelerate infrastructure and interventions. We conclude with recommendations for those considering developing a NIC to promote diversity, equity, and inclusion efforts.

Three-dimensional printing of poly(glycerol sebacate fumarate) gadodiamide-poly(ethylene glycol) diacrylate structures and characterization of mechanical properties for soft tissue applications.

Bioresorbable materials have been frequently used to three-dimensional (3D) print biomedical structures. In this study, we developed a technique to 3D print poly(glycerol sebacate fumarate) gadodiamide (Rylar)-poly(ethylene glycol) diacrylate (PEGDA) samples and investigated their mechanical and thermal properties as a function of (PS) and ultraviolet intensity (UVI). The Young's modulus (E), ultimate tensile strength (UTS), failure strain (ɛF ), and glass transition temperature (Tg ) showed strong correlation with PS and UVI. Results showed E to be between 1.31 and 3.12 MPa, UTS between 0.07 and 0.43 MPa, and ɛF between 7 and 20% with brittle failure. The Tg was observed to lie between -54.48 and -49.10 °C without secondary/tertiary transitions. Dominant elastic behavior was observed from the dynamic mechanical testing viscoelastic data. Testing results were used to develop a regression predictive model for E as a function of PS and UVI. The model performance was evaluated experimentally with an average absolute error of 3.62%. The E and stress-strain response of our 3D printed samples show agreement with published data for human tracheal cartilage, and the mechanical properties were comparable to other published soft polymeric scaffolds/patches. The E' moduli were also similar to bovine articular cartilage. We have successfully demonstrated that Rylar, a novel bioresorbable radiopaque polymer, when blended with PEGDA can be 3D printed controllably for soft tissue applications such as airway obstructions. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 664-671, 2019.

Finite Element Analysis of Descemet's Stripping Automated Endothelial Keratoplasty (DSAEK) Surgery Allograft to Predict Endothelial Cell Loss.

PURPOSE: To develop high fidelity finite element (FE) models of the Descemet's stripping automated endothelial keratoplasty (DSAEK) allograft to estimate the stress distributions generated on the allograft during its deformed state in popular allograft insertion configurations and qualitatively correlate the stress distributions to postsurgical endothelial cell (EC) loss. MATERIALS AND METHODS: Corneal allograft simulation was performed using ANSYS (Canonsburg, PA, USA) utilizing isotropic nonlinear hyperelastic corneal material properties to evaluate the stress distributions generated on the DSAEK allograft during popular allograft insertion configurations, namely forceps, taco, and double-coil insertion configurations. The gathered FE simulation results were qualitatively compared with published clinical studies to verify the simulation results. RESULTS: The FE simulation results demonstrate that high stress regions predicted by FE model results correctly predict the areas of postsurgical EC loss as published in the studies available in open literature. The FE simulation stress magnitude results suggest that highest EC loss due to mechanical bending trauma occurs in double-coil configuration followed by forceps and then taco configuration. CONCLUSIONS: The results of the presented FE simulation study highlight that allograft regions with high stress distribution demonstrate postsurgical EC loss in clinical studies. The modeling procedures presented in this research can be utilized to develop novel surgical devices/techniques that can modulate the postsurgical EC loss due to mechanical bending trauma and facilitate allograft unfolding inside the AC, thereby improving the results of the DSAEK surgical procedure.

Descemet's Stripping Automated Endothelial Keratoplasty Tissue Insertion Devices.

This review study provides information regarding the construction, design, and use of six commercially available endothelial allograft insertion devices applied for Descemet's stripping automated endothelial keratoplasty (DSAEK). We also highlight issues being faced in DSAEK and discuss the methods through which medical devices such as corneal inserters may alleviate these issues. Inserter selection is of high importance in the DSAEK procedure since overcoming the learning curve associated with the use of an insertion device is a time and energy consuming process. In the present review, allograft insertion devices were compared in terms of design, construction material, insertion technique, dimensions, incision requirements and endothelial cell loss to show their relative merits and capabilities based on available data in the literature. Moreover, the advantages/disadvantages of various insertion devices used for allograft insertion in DSAEK are reviewed and compared. The information presented in this review can be utilized for better selection of an insertion device for DSAEK.