MSGID: 1:317/3 6274a473   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    Self-propelled, endlessly programmable artificial cilia    
    Simple microstructures that bend, twist and perform stroke-like motions   
   could be used for soft robotics, medical devices and more    
      
     Date:   
         May 5, 2022   
     Source:   
         Harvard John A. Paulson School of Engineering and Applied Sciences   
     Summary:   
         Researchers have developed a single-material, single-stimuli   
         microstructure that can outmaneuver even living cilia. These   
         programmable, micron-scale structures could be used for a range   
         of applications, including soft robotics, biocompatible medical   
         devices, and even dynamic information encryption.   
      
      
      
   FULL STORY   
   ==========================================================================   
   For years, scientists have been attempting to engineer tiny,   
   artificial cilia for miniature robotic systems that can perform complex   
   motions, including bending, twisting, and reversing. Building these   
   smaller-than-a-human-hair microstructures typically requires multi-step   
   fabrication processes and varying stimuli to create the complex movements,   
   limiting their wide-scale applications.   
      
      
   ==========================================================================   
   Now, researchers from the Harvard John A. Paulson School of Engineering   
   and Applied Sciences (SEAS) have developed a single-material,   
   single-stimuli microstructure that can outmaneuver even living   
   cilia. These programmable, micron-scale structures could be used for a   
   range of applications, including soft robotics, biocompatible medical   
   devices, and even dynamic information encryption.   
      
   The research is published inNature.   
      
   "Innovations in adaptive self-regulated materials that are capable of a   
   diverse set of programmed motions represent a very active field, which is   
   being tackled by interdisciplinary teams of scientists and engineers,"   
   said Joanna Aizenberg, the Amy Smith Berylson Professor of Materials   
   Science and Professor of Chemistry & Chemical Biology at SEAS and senior   
   author of the paper. "Advances achieved in this field may significantly   
   impact the ways we design materials and devices for a variety of   
   applications, including robotics, medicine and information technologies."   
   Unlike previous research, which relied mostly on complex multi-component   
   materials to achieve programmable movement of reconfigurable structural   
   elements, Aizenberg and her team designed a microstructure pillar made of   
   a single material -- a photoresponsive liquid crystal elastomer. Because   
   of the way the fundamental building blocks of the liquid crystal elastomer   
   are aligned, when light hits the microstructure, those building blocks   
   realign and the structure changes shape.   
      
   As this shape change occurs, two things happen. First, the spot where   
   the light hits becomes transparent, allowing the light to penetrate   
   further into the material, causing additional deformations. Second,   
   as the material deforms and the shape moves, a new spot on the pillar   
   is exposed to light, causing that area to also change shape.   
      
      
      
   ==========================================================================   
   This feedback loop propels the microstructure into a stroke-like cycle   
   of motion.   
      
   "This internal and external feedback loop gives us a self-regulating   
   material.   
      
   Once you turn the light on, it does all its own work," said Shucong Li,   
   a graduate student in the Department of Chemistry and Chemical Biology   
   at Harvard and co-first author of the paper.   
      
   When the light turns off, the material snaps back to its original shape.   
      
   The material's specific twists and motions change with its shape, making   
   these simple structures endlessly reconfigurable and tunable. Using a   
   model and experiments, the researchers demonstrated the movements of   
   round, square, L- and T-shaped, and palm-tree-shaped structures and laid   
   out all the other ways the material can be tuned.   
      
   "We showed that we can program the choreography of this dynamic dance   
   by tailoring a range of parameters, including illumination angle, light   
   intensity, molecular alignment, microstructure geometry, temperature,   
   and irradiation intervals and duration," said Michael M. Lerch, a   
   postdoctoral fellow in the Aizenberg Lab and co-first author of the paper.   
      
   To add another layer of complexity and functionality, the research team   
   also demonstrated how these pillars interact with each other as part of   
   an array.   
      
   "When these pillars are grouped together, they interact in very complex   
   ways because each deforming pillar casts a shadow on its neighbor, which   
   changes throughout the deformation process," said Li. "Programming how   
   these shadow- mediated self-exposures change and interact dynamically with   
   each other could be useful for such applications as dynamic information   
   encryption."  "The vast design space for individual and collective motions   
   is potentially transformative for soft robotics, micro-walkers, sensors,   
   and robust information encryption systems," said Aizenberg.   
      
   The paper was co-authored by James T. Waters, Bolei Deng, Reese   
   S. Martens, Yuxing Yao, Do Yoon Kim, Katia Bertoldi, Alison Grinthal   
   and Anna C. Balazs. It was supported in part by the U.S. Army Research   
   Office, under grant number W911NF-17-1-0351 and the National Science   
   Foundation through the Harvard University Materials Research Science   
   and Engineering Center under award DMR- 2011754.   
      
      
   ==========================================================================   
   Story Source: Materials provided by   
   Harvard_John_A._Paulson_School_of_Engineering_and_Applied   
   Sciences. Original written by Leah Burrows. Note: Content may be edited   
   for style and length.   
      
      
   ==========================================================================   
   Journal Reference:   
      1. Shucong Li, Michael M. Lerch, James T. Waters, Bolei Deng, Reese S.   
      
         Martens, Yuxing Yao, Do Yoon Kim, Katia Bertoldi, Alison Grinthal,   
         Anna C. Balazs, Joanna Aizenberg. Self-regulated non-reciprocal   
         motions in single-material microstructures. Nature, 2022; 605   
         (7908): 76 DOI: 10.1038/s41586-022-04561-z   
   ==========================================================================   
      
   Link to news story:   
   https://www.sciencedaily.com/releases/2022/05/220505205924.htm   
      
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