# Mechanical Design of DNA Origami in the Classroom
## 4 Discussion  
Here, we demonstrated the ability to fold a series of compliant DO structures and analyze their conformations via agarose gel electrophoresis with the use of low-cost portable equipment that is well-suited for classroom implementation. The folding can be carried out in \(\sim\)20 min, and the gel electrophoresis can be carried out in \(\sim\)40 min. Including sample and experiment preparation time, the full module can be completed in a 2 h laboratory period, or if prep work is done ahead of time, the folding and gel analysis can be carried out within ~1 h. The cost of the materials needed for these educational experiments is relatively low. Based on the typical costs of DNA staple and scaffold strands (see details of cost estimates here: [33]), we estimate the costs for the material required for five lab groups to be ~$1-5. Hence, an educator could order materials for ~$10-100 to cover the materials for a full semester or year for a typical sized class. Costs could be slightly higher, as materials often have to be purchased in some minimum amount. In the future, we envision that kits could be produced to provide all the required materials and reagents in amounts appropriate for one class for one semester. The major cost savings is in avoiding the need for expensive equipment. We focused on demonstrating these modules with equipment that is readily available in many science classrooms or is relatively low-cost. It is likely possible to further simplify the educational experiments or adapt them based on available equipment. For example, a microwave could be used to heat a water beaker and then placed in insulation once at the correct temperature. The folding could also likely be carried out with insulation to achieve slow cooling, instead of a constant temperature. However, since annealing rates may vary based on the insulation setup, maintaining a constant temperature (52 \(\pm\) 1 \({}^{\circ}\)C) would likely lead to more consistent results. One opportunity to enhance the modules could be to expose students to imaging methods for direct visualization. Here, we visualized structures by TEM, which is not practical for classroom implementation. However, images provided here (including Supporting Information) could be provided to students to give structural context for the observed changes in gel mobility. Another option for direct visualization is atomic force microscopy (AFM), which may be feasible for classroom implementation given some possible low-cost custom-built options [54]. This experiment module could be presented as a stand-alone experience or in combination with our previously established experiment module focused on the folding of a static DO nanostructure [26]. In either case, from the fabrication and analysis, students can learn basic biology skills such as pipetting, mixing reactions, DNA annealing, agarose gel electrophoresis, and UV imaging. Students are also exposed to DNA origami nanotechnology concepts, which can connect to and reinforce mechanical engineering concepts through mechanical models of structure deformation. We propose a set of learning outcomes in Supporting Table S4 that could be adopted, edited, or added to for future use by educators implementing the module into a classroom. Furthermore, this work focuses on introducing the strong connection between compliant DO structures and mechanical design. To highlight this connection, we implemented pseudo-rigid-body models and small-deformation bending models to describe the deformed state of the compliant hinge. Importantly, these approaches agree reasonably with the experimental results while relying on, reinforcing, and providing new application context for undergraduate-level engineering mechanics. The force balance was employed to build up the connection between the ssDNA linkers and the bending of the compliant joint.