4D Printing
Four-dimensional (4D) printing relies on multimaterial printing, reinforcement patterns, or micro/nanofibrous additives as programmable tools to achieve desired shape reconfigurations. However, existing programming approaches still follow the so-called origami design principle to generate reconfigurable structures by self-folding stacked 2D materials, particularly at small scales. Here, we propose a programmable modular design that directly constructs 3D reconfigurable microstructures capable of sophisticated 3D-to-3D shape transformations by assembling 4D micro-building blocks. 4D direct laser writing is used to print two-photon polymerizable, stimuli-responsive hydrogels to construct building blocks at micrometer scales. Denavit-Hartenberg (DH) parameters, used to define robotic arm kinematics, are introduced as guidelines for how to assemble the micro-building blocks and plan the 3D motion of assembled chain blocks. Last, a 3D-printed microscaled transformer capable of changing its shape from a race car to a humanoid robot is devised and fabricated using the DH parameters to guide the motion of various assembled compartments.
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T.-Y. Huang*, H.-W. Huang*, D. Jin*, Q. Chen, J. Huang, L. Zhang, H. Duan, “4D-Printed Micro-Building Blocks,” Science Advances 6 (3), eaav8219 (*Equal contribution)
Adaptive locomotion of artificial microswimmers
Bacteria can exploit mechanics to display remarkable plasticity in response to locally changing physical and chemical conditions. Compliant structures play a notable role in their taxis behavior, specifically for navigation inside complex and structured environments. Bioinspired mechanisms with rationally designed architectures capable of large, nonlinear deformation present opportunities for introducing autonomy into engineered small-scale devices. This work analyzes the effect of hydrodynamic forces and rheology of local surroundings on swimming at low Reynolds number, identifies the challenges and benefits of using elastohydrodynamic coupling in locomotion, and further develops a suite of machinery for building untethered microrobots with self-regulated mobility. We demonstrate that coupling the structural and magnetic properties of artificial microswimmers with the dynamic properties of the fluid leads to adaptive locomotion in the absence of on-board sensors.
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H.-W. Huang, M. Tibbitt, T.-Y. Huang, and B. J. Nelson, “Matryoshka-Inspired Micro-origami Capsules for Enhanced Drug Loading, Encapsulation, and Transportation,” Soft Robotics
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H.-W. Huang, T.-Y. Huang, M. Charilauo, S. Lyttle, Q. Zhang, S. Pané, and B. J. Nelson, “Investigation of Magnetotaxis of Reconfigurable Micro-origami Swimmers with Competitive and Cooperative Anisotropy,” Advanced Functional Materials, 1802100, 2018
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H.-W. Huang, R. E. Uslu, P. Katsamba, E. Lauga, M. S. Sakar and B. J. Nelson, “Adaptive Locomotion of Artificial Microswimmers” Science Advances, vol. 5, no. 1, 2019
Optimization of Artificial bacteria
Recent advances in smart materials and microfabrication techniques lead to the development of microrobots for on-demand and targeted therapy. Self-folded hydrogel tubes are particularly promising vehicles as they provide relatively large surface area-to-volume ratio and cargo space for therapeutic agents. In this paper, we decorate these microstructures with an artificially approximated bacterial flagellum to enable efficient swimming in fluidic environments. Flexibility enhances overall motility of the soft microrobot through synergistic propulsion generated by the tubular body and the flagellum, a feature that has not been observed in conventional microrobots manufactured from rigid materials. While the flagellum is applying forward thrust, a precession is induced on the body due to wobbling of the tail that can provide extra speed depending on the tail design. A simple model based on resistive force theory explains the direction-dependent changes in swimming motility and the role of tail geometry.
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H.-W. Huang, A. J. Petruska, B. J. Nelson, “Soft Microrobots in Military Medicine,” HDIAC Journal, 2017
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H.-W. Huang, Q. W. Chao, M. S. Sakar, and B. J. Nelson, “Optimization of tail geometry for the propulsion of soft microrobots,” IEEE Robotics and Automation Letters 2017 (Accepted)
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H.-W. Huang, M. S. Sakar, A. J. Petruska, S. Pané, and B. J. Nelson, ”Soft micromachines with programmable motility and morphology,” Nature Communication, vol. 7, 2016.
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H.-W Huang, M. S. Sakar, B. J. Nelson, “Biomimetic Soft Micromachines with Programmable Morphology and Motility,” Proc. In MaP Graduate Symposium, June 2016. ​
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H.-W Huang, M. S. Sakar, B. J. Nelson, “Controlling formations of multiple mobile micromachines,” Fluid Mechanics and Collective Behavior: From Cells to Organisms, Congressi Steffano Franscini (CSF) Conference, 2016
Microrobots with addressible shape control
Recent advances in smart materials and microfabrication techniques lead to the development of microrobots for on-demand and targeted therapy. Self-folded hydrogel tubes are particularly promising vehicles as they provide relatively large surface area-to-volume ratio and cargo space for therapeutic agents. In this paper, we decorate these microstructures with an artificially approximated bacterial flagellum to enable efficient swimming in fluidic environments. Flexibility enhances overall motility of the soft microrobot through synergistic propulsion generated by the tubular body and the flagellum, a feature that has not been observed in conventional microrobots manufactured from rigid materials. While the flagellum is applying forward thrust, a precession is induced on the body due to wobbling of the tail that can provide extra speed depending on the tail design. A simple model based on resistive force theory explains the direction-dependent changes in swimming motility and the role of tail geometry.
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H.-W Huang, M. S. Sakar, K. Riederer, N. Shamsudhin, A. Petruska, S. Pané, and B. J. Nelson, “Magnetic Microrobots with Addressable Shape Control,” IEEE International Conference on Robotics and Automation, Stockholm, Sweden, (ICRA 2016)
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H.-W Huang, A. J. Petruska, M. S. Sakar, M. Skoura, F. Ulrich, Q. Zhang, S. Pane, and B. J. Nelson, “Self-folding Hydrogel Bilayer for Enhanced Drug Loading, Encapsulation, and Transport,” 38 th Annual International Conference of the Engineering in Medicine and Biology Society, Orlando, FL USA (EMBC’16)
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S. Fusco, H.-W. Huang, K. Peyer, C. Peters, M. Haberli, A. Ulbers, A. Spyrogianni, E. Pellicer, J. Sort, S. Prastinis, B. Nelson, S. M. Sakar, and S. Pane, "Shape-switching microrobots for medical applications : the influence of shape in drug delivery and locomotion," ACS Applied Materials & Interfaces, vol. 7, no. 12, pp. 6803-6811, 2015.
Magnetic microgrippers
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J.-C. Kuo, H.-W. Huang and Y.-J. Yang, “A hydrogel-based intravascular microgripper manipulated using magnetic fields”, Sensors and Actuators A: Physical, vol. 211, pp. 121-130, 2014.