publications

2022

1. Active entanglement enables stochastic, topological grasping

   Kaitlyn Becker, Clark Teeple, Nicholas Charles, and 5 more authors

   Proceedings of the National Academy of Sciences Oct 2022

   Abs

   Grasping, in both biological and engineered mechanisms, can be highly sensitive to the gripper and object morphology, as well as perception and motion planning. Here, we circumvent the need for feedback or precise planning by using an array of fluidically actuated slender hollow elastomeric filaments to actively entangle with objects that vary in geometric and topological complexity. The resulting stochastic interactions enable a unique soft and conformable grasping strategy across a range of target objects that vary in size, weight, and shape. We experimentally evaluate the grasping performance of our strategy and use a computational framework for the collective mechanics of flexible filaments in contact with complex objects to explain our findings. Overall, our study highlights how active collective entanglement of a filament array via an uncontrolled, spatially distributed scheme provides options for soft, adaptable grasping.

2. Thermodynamics of Hygroresponsive Soft Engines: Cycle Analysis and Work Ratio

   Beomjune Shin, Yeonsu Jung, Munkyeong Choi, and 1 more author

   Physical Review Applied Oct 2022
3. Evaporative capillary rise

   Jungtaek Kim, Yeonsu Jung, and Ho-Young Kim

   Physical Review Fluids Mar 2022

2021

1. Avian mud nest architecture by self-secreted saliva

   Yeonsu Jung, Sohyun Jung, Sang-im Lee, and 2 more authors

   Proceedings of the National Academy of Sciences Jan 2021

   Abs

   Significance We provide a biomechanical explanation of how swallows and phoebes can construct strong nests of incohesive mud granules using saliva as a paste. The analysis leads to a hypothesis for why only 57 small light-weighted bird species (of approximately 10,000 species worldwide) can build mud nests on walls by utilizing their saliva. Our comprehensive study, combining experiments on natural and artificial mud nests and mathematical models on granular cohesion, not only elucidates the physical mechanism of this extraordinary animal architecture, but also provides inspiration to three-dimensional printing technology based on environmentally benign granular materials. , Mud nests built by swallows (Hirundinidae) and phoebes ( Sayornis ) are stable granular piles attached to cliffs, walls, or ceilings. Although these birds have been observed to mix saliva with incohesive mud granules, how such biopolymer solutions provide the nest with sufficient strength to support the weight of the residents as well as its own remains elusive. Here, we elucidate the mechanism of strong granular cohesion by the viscoelastic paste of bird saliva through a combination of theoretical analysis and experimental measurements in both natural and artificial nests. Our mathematical model considering the mechanics of mud nest construction allows us to explain the biological observation that all mud-nesting bird species should be lightweight.

2. Soft artificial electroreceptors for noncontact spatial perception

   Won Jun Song, Younghoon Lee, Yeonsu Jung, and 6 more authors

   Science Advances Nov 2021

   Abs

   Soft artificial electroreceptors inspired by electroreception mechanism of rays can locate objects in a noncontact manner. , Elasmobranch fishes, such as sharks, skates, and rays, use a network of electroreceptors distributed on their skin to locate adjacent prey. The receptors can detect the electric field generated by the biomechanical activity of the prey. By comparing the intensity of the electric fields sensed by each receptor in the network, the animals can perceive the relative positions of the prey without making physical contact. Inspired by this capacity for prey localization, we developed a soft artificial electroreceptor that can detect the relative positions of nearby objects in a noncontact manner by sensing the electric fields that originate from the objects. By wearing the artificial receptor, one can immediately receive spatial information of a nearby object via auditory signals. The soft artificial electroreceptor is expected to expand the ways we can perceive space by providing a sensory modality that did not evolve naturally in human beings.

2020

1. Ionic spiderwebs

   Younghoon Lee, Won Jun Song, Yeonsu Jung, and 4 more authors

   Science Robotics Jul 2020

   Abs

   Ionic spiderwebs emulate the capturing strategies of a spider with a single pair of threads based on electrostatics. , Spiders use adhesive, stretchable, and translucent webs to capture their prey. However, sustaining the capturing capability of these webs can be challenging because the webs inevitably invite contamination, thus reducing its adhesion force. To overcome these challenges, spiders have developed strategies of using webs to sense prey and clean contaminants. Here, we emulate the capturing strategies of a spider with a single pair of ionic threads based on electrostatics. Our ionic spiderwebs completed consecutive missions of cleaning contamination on itself, sensing approaching targets, capturing those targets, and releasing them. The ionic spiderwebs demonstrate the importance of learning from nature and push the boundaries of soft robotics in an attempt to combine mutually complementary functions into a single unit with a simple structure.

2019

1. A design principle of root length distribution of plants

   Yeonsu Jung, Keunhwan Park, Kaare H. Jensen, and 2 more authors

   Journal of The Royal Society Interface Dec 2019

   Abs

   Shaping a plant root into an ideal structure for water capture is increasingly important for sustainable agriculture in the era of global climate change. Although the current genetic engineering of crops favours deep-reaching roots, here we show that nature has apparently adopted a different strategy of shaping roots. We construct a mathematical model for optimal root length distribution by considering that plants seek maximal water uptake at the metabolic expenses of root growth. Our theory finds a logarithmic decrease of root length density with depth to be most beneficial for efficient water uptake, which is supported by biological data as well as our experiments using root-mimicking network systems. Our study provides a tool to gauge the relative performance of root networks in transgenic plants engineered to endure a water deficit. Moreover, we lay a fundamental framework for mechanical understanding and design of water-absorptive growing networks, such as medical and industrial fluid transport systems and soft robots, which grow in porous media including soils and biotissues.

2018

1. Poro-elasto-capillary wicking of cellulose sponges

   Jonghyun Ha, Jungchul Kim, Yeonsu Jung, and 3 more authors

   SCIENCE ADVANCES Dec 2018

2016