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Compliant DNA Origami Mechanisms (Collaboration with Dr. Haijun Su)

The concept of compliant mechanism design provides a promising strategy for the fabrication of machines at the nano and micro scale.In compliant mechanisms, specified motion is obtained by the strategic arrangment of components of varying stiffness. This allows motion without the need for very flexible joints. This approach has been established for a range of macroscopic systems. In collaboration with Dr. Haijun Su, our lab is pioneering the development of nanoscale compliant mechanisms. The ability to achieve controlled motion with the use of flexible components is particularly promising for nanomachines because of the potential to overcome Brownian motion (thermal fluctuations). Thermal fluctuations are the consistent random motions imparted by the energy of the surrounding solution. An example of thermal fluctuations is shown here for a DNA origami filament consisting of 6 bundled helices of DNA imaged in our lab by total internal reflection fluorescence microscopy. The filament is approximately 7 μm long. Overcoming this random motion is a critical challenge to enable nanomachines with controllable motion.

We are developing a novel approach to create nanoscale moving systems based on a compliant mechanism design approach. Compliant mechanisms require the ability to create components of varying stiffness. We have built DNA origami nanostructures that function as compliant joints with tunable stiffness. The structures are comprised of comprised of double-stranded DNA (dsDNA) and single-stranded DNA (ssDNA) elements. In the design, the two arms on either side are highly stiff and can be considered as essential rigid. The central portion consists of a layer of dsDNA helices and several ssDNA connections. The entropic tension in the ssDNA balances the bending energy in the dsDNA layer to create a compliant joint where the angle, , and the stiffness can be tuned by adjusting the length of the ssDNA connections. We introduced a ssDNA loop in the structure for straightforward changing of the structure properties. The scale bars in the images are 20 nm.

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Compliant components like the one shown above will for the basis of our future efforts to make compliant machines such as the nanoscale manipulator shown here that functions similar to a macroscopic robot arm.

Research team: Lifeng Zhou, Alex Marras

This project is based on work that was supported by: NSF Engineering and Systems Design (ESD) program

Also check out our related work on designing DNA origami machines and mechanisms.