# Mechanical Design of DNA Origami in the Classroom
## 1 Introduction
(**F**): DNA origami compliant nanostructures; conversion from double-stranded to single-stranded DNA induces forces that drive deformation into distinct conformations [22]. (**G**): DNA origami rotary ratchet motor [25]. Generally, DNA nanotechnology studies rely on a variety of principles from multiple disciplines in science and engineering, thus making it an excellent field for interdisciplinary education modules. Useful general introductions to structural DNA nanotechnology can be found in a number of review or research articles [26; 27; 28; 29]. Recent work has taken important steps to translate simpler DNA constructs into classroom experiments [30; 31], introducing concepts such as conformational changes, DNA structural motifs, and nanostructure biostability. However, translating more complex DO into educational experiences has been challenging, due to the complexity of design, long time periods for experiments, and relatively high cost of materials and equipment. Hence, the study of complex DO devices has been limited mainly to research institutions in graduate-level laboratories with significant prior expertise and well-equipped laboratories. In an effort to lower this barrier, we recently presented classroom-friendly methods for the fabrication and analysis of DO structures [26]. These methods leverage the ability to fold DO rapidly at constant temperature [32] and the ability to fold DO with low-cost equipment [33]. Building on those advances, we developed an educational experiment module to demonstrate the basic methods and concepts for folding a simple static DO nanorod design [26]. The fabrication utilizes simple heated water baths, consisting of water-filled beakers heated on hot plates, to carry out folding on the time scale of ~15 min. The analysis consists of an evaluation of folding via agarose gel electrophoresis that can be carried out within ~40 min on a cost-effective MiniOne gel electrophoresis system designed for classroom implementation. Including sample and experiment prep time, the module can be completed in ~90-120 min, or in ~60 min if experiment prep work is done beforehand. Here, we continue advancing the educational translation of DO nanotechnology with a focus on introducing the mechanical design of DNA nanostructures [34]. We present the optimized fabrication and analysis of a DO 'compliant hinge joint' (CHJ) structure [35] that can be folded into multiple configurations with varying degrees of mechanical deformation. The different configurations are achieved by substituting a small subset of the constituent DNA strands, leveraging the concept of modular design. We demonstrate that the different configurations result in different mobilities in gel electrophoresis using classroom-ready gel equipment. As with the previous module [26], the experiments can be completed within a ~120 min laboratory period including sample and experiment prep or within a ~60 min classroom period (~15-20 min folding and ~40-45 min gel electrophoresis) if experiment and sample prep is done beforehand. Additionally, to expand upon these education experiment modules and introduce the interdisciplinary integration of DNA nanotechnology and mechanical design to science and engineering classrooms, we also propose two mechanical models based on beam-bending that relate the nanostructure properties to the resulting deforming structure.