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Recreating articular cartilage tri-layered patterning for an engineered in vitro cell construct holds promise for advancing cartilage repair efforts. Our approach involves the development of a mul-tichambered perfusion tissue bioreactor that regulates fluid shear stress levels similar to the gradated hydrodynamic environment in articular cartilage. COMSOL modeling reveals our ta-pered cell chamber design will produce three different shear levels, high in the 22 – 41 mPa range, medium in the 4.5 – 8.4 mPa range, and low in the 2.2 – 3.8 mPa range and distributed across the surface of our mesenchymal stromal cell (MSC) encapsulated construct. In a 14-day bioreactor culture, we assess how fluid shear magnitude and cell vertical location within a 3D construct influence cell chondrogenesis. Notably, Sox9 expression for MSCs cultivated in our reactor shows spatially patterned gene upregulations coding for key chondrogenic marker pro-teins. Beginning with the high shear stress region, lubricin and type II collagen gene increases of 410 and 370-fold indicate cell movement towards a superficial zone architype which is further supported by histological and immunohistochemical stains illustrating the formation of a dense proteoglycan matrix enriched with lubricin, versican, and collagen types I and II molecules. For the medium shear stress region high aggrecan and type II collagen gene expressions of 2.3 and 400-fold, respectively, along with high proteoglycan analyses show movement toward a superfi-cial/mid-zone cartilage architype. For low shear stress regions higher collagen types II and X gene upregulations of 550 and 8,300-fold, the latter being 2x of that for the high shear regime, indicate cell movement with deep zone characteristics. Collectively, biochemical analysis, histol-ogy, and gene expression data demonstrated that our fluid shear bioreactor induced a stratified structure within tissue engineered constructs, demonstrating the feasibility of using this ap-proach to recapitulate the structure of native articular cartilage. 

Hands-on, active learning in engineering courses fosters deeper understanding, collaboration, and social skills for students. This paper reports on the design, fabrication, and testing of a transparent miniaturized shell-and-tube heat exchanger module for engineering thermo-fluids classes. This module was also implemented for in-class heat exchanger instruction, where students (sample size, N = 75) conducted hands-on experiments following the instructions provided in the associated worksheet, participated in pre-tests and post-tests, analyzed the experimental data, and provided their feedback through motivational surveys. The performance test data obtained from the developed desktop heat exchanger module shows that the experimental heat transfer rates are in good agreement with theoretically predicted values calculated based on the standard correlations and assumptions. The pre-test and post-test assessments show that the use of this miniaturized shell-and-tube heat exchanger module in classroom instruction improves fundamental understanding of the heat exchange process and enhances student comprehension of complex phenomena of fluid flow patterns and heat transfer in the different parts of the heat exchanger. The motivational assessments demonstrate the module’s efficacy in elucidating the underlying heat transfer mechanisms and facilitating active engagement. The developed low-cost, handson heat exchanger can be used in undergraduate thermo-fluids engineering education for visualizing and better understanding of heat transfer principles, enhancing engagement of students, improving retention of fundamental concepts, and finally bridging the gap between theoretical abstractions and real-world applications. 

In this study we examined the first-time use of a miniaturized fluidized bed module in a chemical engineering classroom. Learning activities were developed to foster learning at the higher levels of Bloom's taxonomy and within the ICAP framework to provide interactive, constructive, and active engagement to promote a deeper understanding of concepts. A hands-on activity facilitated by a desktop-scale fluidized bed and reinforcing printed worksheet materials was deployed within a 50-minute class to encourage student engagement. Results from module performance tests compare well to predictions based on theoretical models suggesting this tool can effectively demonstrate fundamental concepts related to pressure loss in a packed bed, minimum fluidization velocity, constant pressure drop in a fluidized bed, bed expansion and repacking below a top screen. Pre- and Posttests 1 and 2 show student learning was significantly improved after pre-homework and the hands-on activity compared to the learning after the lecture alone. Student responses to two open-ended questions on Pre- and Posttests 1 and 2 allowed us to identify persisting student misconceptions about packed and fluidized beds. Suggestions for future work to repair these misconceptions are included in this study. 

Over the past seven years, our team has disseminated low-cost hands-on learning hardware and associated worksheets in fluid mechanics and heat transfer to provide engineering students with an interactive learning experience. Previous studies have shown (1-5) the efficacy of teaching students with an active learning approach versus a more traditional lecture setup, with a number of approaches already available, such as simple active discussion, think-pair-share, flipped classrooms, etc. Our approach is differentiated by the inclusion of hardware to add both a visual aid and an opportunity for hands-on experimentation while keep the costs low enough for a classroom setting. Learning with a hands-on, interactive approach is supported by social cognitive theory (SCT) (6-7) and information processing theory (8). Unlike earlier views of learning theory, which simply posit that the key to learning is repetition, social cognitive theory considers the agency of the student and the social aspects of learning. The primary assumption of SCT is that students are active participants in the learning process, acquiring and displaying knowledge, skills, and behaviors that align with their goals through a process called triadic reciprocal causation, illustrated in figure 1. 

Introduction: Directing mesenchymal stem cell (MSC) chondrogenesis by bioreactor cultivation provides fundamental insight towards engineering healthy, robust articular cartilage (AC). The mechanical environment is represented by compression, fluid shear stress, hydrostatic pressure, and tension which collectively contribute to the distinct spatial organization of AC. Mimicking this cell niche is necessary for dictating cell growth, fate, and role. Researchers have shown that different mechanical stimulus types improve MSC chondrogenic commitment demonstrated by increases in key chondrogenic gene and protein markers. However, challenges remain in manufacturing spatially, anisotropic AC consisting of defined regions such as native tissue. Our strategy towards furthering this effort involves exposing MSC-laden alginate scaffolds in a multi-chambered, perfusion bioreactor with controlled fluid shear stress magnitudes to better mimic the native AC microenvironment leading to defined regions throughout the scaffold marked by varied cellular phenotypes. Validations made from assessing biochemical content, mRNA expression, western blot analysis, and cell viability will provide meaningful insight towards regulating MSC chondrogenesis. Methods: MSCs grown up to passage 4 were expanded to confluency in a T-175 flask then released from the surface using trypsin. Cells were stored in -80 ℃ freezer until experimentation. Our bioreactor system was sterilized by UV radiation for 4 hours then perfused with 70% ethanol overnight. Cell-laden scaffolds were prepared by first dissolving 1.5% alginate into deionized water. The polymeric solution was sterilely filtered and stored until usage. Cryopreserved MSCs were thawed and suspended in α-MEM medium containing essential supplements. Cells were counted and resuspended in alginate at a density of 106 cells/mL. The mixture was transferred to our multi-chambered bioreactor where they were allowed to crosslink in CaCl2 solution for 45 min. Separate scaffolds (N = 3) were molded within an identical reactor system and removed to serve as a control to compare effects of fluid shear stress on MSC differentiation. All, structures were washed with PBS then supplied with DMEM/F-12 medium containing 10% FBS, 1% penicillin/streptomycin , 1% L-glutamine, 100 nM dexamethasone, 50 µg/mL L-ascorbic acid, and10 ng/mL TGF-β3. The flowrate for the bioreactor was adjusted to 20 mL/min which provided desired fluid shear ranges of 2-87 mPa to stimulate the cells . Cell cultures were grown for 7 days, and medium changed every 3 days. Sectioned samples were analyzed for biochemical content, mRNA expression, and western blot to understand the impact of fluid shear stress magnitudes on MSC differentiation. Results: Directed fluid shear stress across a cell-laden alginate scaffold contained within an individual chamber in our bioreactor indicates varied cellular behavior within the superficial and deep regions of the construct marked by spatially secreted biochemical content as well as mRNA expression. This observation is supported by superficial MSCs stimulated by high and medium mechanical stimulation which indicates a 1.3 and 1.2-fold increase in total collagen production, respectively, when directly compared to cells deep in the construct. A similar effect is supported by total GAG secretion where high and medium shear stress across the fluid hydrogel interface yielded 1.2 and 1.3-fold upregulation of protein secretion, respectively, when observed under similar conditions. Perfused MSCs show upregulation to 3 and 20-fold for Sox9 and aggrecan, respectively, compared to a static culture. Shear ranges distributed throughout our cell-laden alginate scaffold correlates to differential chondrogenic commitment shown by variance of Sox9 expression when assessed by location and depth. Additional information on COL10A1 expression demonstrates mechanical stimulation that reduces hypertrophic cell differentiation contrary to a static culture. Discussion: In this investigation we emphasize that cells respond differently to mechanical stimulation when located in either the superficial or deep region of an alginate scaffold. This observation is supported by enhanced matrix production of chondrogenic protein for cells near the perfused fluid and hydrogel interface compared to deeper areas when stimulated by high and medium fluid shear loading regimes. Most importantly, maintenance of a healthy fluid shear gradient in our TBR provides evidence of promoting MSC chondrogenesis by spatially upregulating anabolic cartilage-like markers in addition to diminishing the onset of cell hypertrophy. Our efforts in monitoring mRNA expression of our samples reveals enhancement of chondrogenic cell differentiation for a perfused sample marked by increases in Sox9 and aggrecan genes; whereas a static sample stimulated only by TGF-β3 leads to undesirable expression of COL10A1. Key takeaways from our study support the contributions from previous researchers in recreating the native AC mechanical environment to encourage MSC differentiation. The development of our TBR system for controlled delivery of fluid shear stresses to MSCs furthers efforts in spatially guiding MSC chondrogenesis which is critical for engineering zonally differentiated AC. 

The goal of the greater project is to provide students with hands-on learning experiences while removing cost as a barrier to participation. Our Low-Cost Desktop Learning Modules (or LCDLMs) help students visualize and experience engineering concepts where books prove less than adequate and provide class members with the opportunity to learn as a group and collaborate with one another. LCDLMs have been found to improve motivation and attention while providing direct and vicarious learning opportunities, encouraging information retention in a learning environment. The goal of this paper is to introduce the latest LCDLM in development, for glucose analysis, which will mark the first LCDLM to feature a chemical reaction. In this paper we will also go over future work to be done to make the glucose analyzer viable for classroom use. The new module will feature a glucose solution meant for analysis, a set of reagents to convert the solution from transparent to a red-violet color of intensity correlated to the glucose concentration, and a simple apparatus students can use to read the concentration of the sample. The apparatus is meant to be used to teach students multiple engineering concepts through visual demonstration. In this LCDLM concept, chemicals from a set of reservoirs flow through a transparent microfluidics mixing chamber, which leads to a colorimetric reaction based on the amount of glucose present, teaching students about kinetics and, to a lesser extent, microfluidics. Dissolved oxygen is a limiting reagent, which will demonstrate to students the relevance of stoichiometry and mass transfer in a closed system. The mixture then collects in a chamber with two transparent sides. Green light passes through the red solution and into the lens of a smartphone camera to measure the intensity of the light. This is meant to demonstrate Beer’s law and complimentary colors. The more light that can pass through, the lower the glucose concentration. Students will need to measure a series of solutions with varied but known concentrations, construct a calibration curve, and then find an unknown solution concentration based on where an absorbance reading falls on the curve, modeling a routine wet lab test but without the need for expensive instrumentation. Prototyping is needed before a definitive version can be implemented in the classroom. The final design for the analyzer, how it will be assembled, parts to be used, etc., is being determined, and up-to-date results will be presented. The geometry of the mixing chamber with attached reservoirs for adding reagents must be optimized for small samples. The plan is to design a 3D model in SolidWorks and then cut out a prototype from an acrylic sheet with a laser cutter. The prototype will then be tested for leaks. The module itself will consist of the channel sheet glued between two other sheets, making assembly straightforward.