Soft Robotics & Devices
We develop soft robotic systems and functional devices by harnessing large deformation, mechanical instabilities, and the unique properties of soft materials. Our research explores how structural design and material response can be used to achieve controlled morphing, actuation, sensing, and fluid manipulation. These principles are applied to systems ranging from pneumatically actuated and snap-through soft robots to tactile sensors, wearable devices, and stretchable sensing platforms.
Snap inflatable modular metastructures for multipath, multimode morphing machines
with Jisung Park, Kanghyun Ki, Jeongyun sun and Hoyoung Kim
Thepractical success ofsoft robotics dependslargely onactuatorswithadvancedshape-morphingcapabilities for tasks suchasdexterousmanipulationandadaptivelocomotion.Traditionalsoftmachineshavefaced limitations caused by the complexity of managing multiple operational modes within a single device. To address this, we introduce highly adaptable morphing machines that combine modular origami and kirigami designs with pneumatic snap-through and snap-back of bistable shells at tile junctions or kirigami creases. Controlled pressure triggers selective snapping at creases, enabling programmed shape transformations along multiple paths. Our analytical and computational framework predicts system morphology and dynamics, guiding the design of snap inflatable modular metastructures (SIMMs). Utilizing SIMMs, we have developed soft robots capable of navigating diverse terrains and performing multifunctional tasks, demonstrated by ‘‘3D spinning ball’’ and ‘‘2D quad-tessellation’’ modes. This research advances morphing capabilities from a single input source, opening new possibilities for applications including minimally invasive surgery and search and rescue.
Related Publication:
Ji-Sung Park, Kanghyun Ki, Anna Lee*, Jeong-Yun Sun*, and Ho-Young Kim*, "Snap inflatable modular metastructures for multi-path, multi-mode morphing machines," Cell Reports Physical Science 6 (2), 102448 (2025). [pdf]
Sequential Multi-Modal Morphing of Single-Input Pneu-Nets
with Han Bi Jeong, Cheongsan Kim, and Ho-Young Kim
Soft actuators provide an attractive means for locomotion, gripping, and deployment of those machines and robots used in biomedicine, wearable electronics, automated manufacturing, etc. In this study, we focus on the shape-morphing ability of soft actuators made of pneumatic networks (pneu-nets), which are easy to fabricate with inexpensive elastomers and to drive with air pressure. As a conventional pneumatic network system morphs into a single designated state, achieving multimodal morphing has required multiple air inputs, channels, and chambers, making the system highly complex and hard to control. In this study, we develop a pneu-net system that can change its shape into multiple forms as a single input pressure increases. We achieve this single-input and multimorphing by combining pneu-net modules of different materials and geometry, while harnessing the strain-hardening characteristics of elastomers to prevent overinflation. Using theoretical models, we not only predict the shape evolution of pneu-nets with pressure change but also design pneu-nets to sequentially bend, stretch, and twist at distinct pressure points. We show that our design strategy enables a single device to carry out multiple functions, such as grabbing—turning a light bulb and holding—lifting a jar.
Related Publication:
Han Bi Jeong, Cheongsan Kim, Anna Lee*, and Ho-Young Kim*, "Sequential multi-modal morphing of single-input pneu-nets," Soft Robotics 10 (6), 1137-1145 (2023). [pdf]
Bistable magnetic valves for selective sweat sampling in wearable microfluidics
with Chaemin Kim, Chanyong Shin, Jonghyun Ha and Jungil Choi
Selective sweat sampling with high spatial and temporal resolution remains a key challenge in wearable microfluidic systems for biochemical monitoring. Here, we present a skin-conformal microfluidic platform that enables targeted, chamber-specific sweat collection by integrating bistable, magneto-active elastomeric valves. Each valve is toggled between open and closed states using a simple external magnetic field, requiring no continuous power. The bistable design provides mechanical memory, maintaining valve states without sustained actuation, and thus allows highly energy-efficient fluid control. By embedding magnetic particles in a shell structure with geometric bistability, we achieve reliable magnetic actuation and characterize the critical pressures associated with valve switching under varying magnetic flux densities. These results demonstrate the feasibility of using the system for practical, localized sweat collection and suggest its utility in wearable sensing applications that require spatially discrete and contamination-free sampling.
Related Publication:
Chaemin Kim, Chanyong Shin, Anna Lee*, Jonghyun Ha*, Jungil Choi*, "Bistable magnetic valves for selective sweat sampling in wearable microfluidics," Lab on a Chip, published online. [pdf]
Stretchable Anisotropic Conductive Film with Position-Registered Conductive Microparticles Used for Strain-Insensitive Ionic Interfacing in Stretchable Ionic Sensors
with Doowon Park, Hyunsu Kwak, Seonghyeon Kim, Hyeongseok Choi, Ighyun Lim, Mingyu Kwak, Iksoo Kim, Hyeji Park,Inyong Eom,Jungwoon Lee,Ikbum Park and Unyong Jeong*
Numerous approaches are explored to achieve precise position registry of microparticles (MPs) with minimal defects; however, MP assembly in a periodic pattern or an arbitrary manner has been a challenging issue over the past several decades. Utilizing the position-registered conductive MPs, polymer composites of the MPs are used as anisotropic conductive film (ACF) and soft interfacing. One of the remaining challenges is maintaining the MP positions while producing or utilizing the ACF. This study proposes a simple strategy to produce a stretchable ACF (S-ACF) by mechanical rubbing, without disturbing the MP positions during the production and use. A practical means of precise MP positioning on a ultraviolet (UV)-patternable soft template is investigated first. This study investigates, through both experiment and finite element method calculation, the relationship between local adhesion of the template and mechanical rubbing variables (pressure, rubbing velocity, and MP size). Based on this exploration, a fast and simple method to fabricate large-area S-ACF is presented. This study demonstrates that the S-ACF can be used for electronic interfacing in stretchable devices and for ionic interfacing to remove the effect of external mechanical force in ionic sensors.
Related Publication:
Doowon Park, Hyunsu Kwak, Seonghyeon Kim, Hyeongseok Choi, Ighyun Lim, Mingyu Kwak, Iksoo Kim, Heyji Park, In-Yong Eom, Jung-Woon Lee, Ikbum Park*, Anna Lee*, and Unyong Jeong*, "Stretchable anisotropic conductive film with position-registered conductive microparticles used for strain-insensitive ionic interfacing in stretchable ionic sensors," Advanced Functional Materials 34 (49), 2408902 (2024). [pdf]
Shear-Pressure Decoupling and Accurate Perception of Shear Directions in Ionic Sensors
with Wonjeong Suh, Kanghyun Ki, Taeyeong Kim, Hyeongseok Choi, and Unyong Jeong
In artificial tactile sensing, to emulate the human sense of touch, independent perception of shear force and pressure is important. Decoupling the pressure and shear force is a challenging task for ensuring stable grasping manipulation for both soft and brittle objects. This study introduces a deformable ion gel-based tactile sensor that is capable of distinguishing pressure from shear force when pressurized shear force is applied in any direction. Recognition of the decoupled forces and precise shear directions is enabled by acquiring tactile data at only two frequencies (20 Hz and 10 kHz) based on the frequency-dependent ion dynamics. This study demonstrates monitoring the changes in pressure, shear force, and shear directions while performing practical robotic actions, such as pouring a water bottle, opening a water bottle cap, and picking up a book and placing it on a shelf.
Related Publication:
Wonjeong Suh, Kanghyun Ki, Taeyeong Kim, Hyeongseok Choi, Anna Lee*, and Unyong Jeong*, "Shear-pressure decoupling and accurate perception of shear directions in ionic sensors by analyzing the frequency-dependent ionic behavior," ACS Applied Materials & Interfaces 15 (44), 51538-51548 (2023). [pdf]