Education & Certifications
M.S., Stanford University, Chemical Engineering (2018)
B.S., Seoul National University, Chemical and Biological Engineering (2015)
- Tuning the Mechanical Properties of a Polymer Semiconductor by Modulating Hydrogen Bonding Interactions CHEMISTRY OF MATERIALS 2020; 32 (13): 5700–5714
- F4-TCNQ as an Additive to Impart Stretchable Semiconductors with High Mobility and Stability ADVANCED ELECTRONIC MATERIALS 2020
Artificial multimodal receptors based on ion relaxation dynamics.
Science (New York, N.Y.)
2020; 370 (6519): 961–65
Human skin has different types of tactile receptors that can distinguish various mechanical stimuli from temperature. We present a deformable artificial multimodal ionic receptor that can differentiate thermal and mechanical information without signal interference. Two variables are derived from the analysis of the ion relaxation dynamics: the charge relaxation time as a strain-insensitive intrinsic variable to measure absolute temperature and the normalized capacitance as a temperature-insensitive extrinsic variable to measure strain. The artificial receptor with a simple electrode-electrolyte-electrode structure simultaneously detects temperature and strain by measuring the variables at only two measurement frequencies. The human skin-like multimodal receptor array, called multimodal ion-electronic skin (IEM-skin), provides real-time force directions and strain profiles in various tactile motions (shear, pinch, spread, torsion, and so on).
View details for DOI 10.1126/science.aba5132
View details for PubMedID 33214277
Stretchable self-healable semiconducting polymer film for active-matrix strain-sensing array.
2019; 5 (11): eaav3097
Skin-like sensory devices should be stretchable and self-healable to meet the demands for future electronic skin applications. Despite recent notable advances in skin-inspired electronic materials, it remains challenging to confer these desired functionalities to an active semiconductor. Here, we report a strain-sensitive, stretchable, and autonomously self-healable semiconducting film achieved through blending of a polymer semiconductor and a self-healable elastomer, both of which are dynamically cross-linked by metal coordination. We observed that by controlling the percolation threshold of the polymer semiconductor, the blend film became strain sensitive, with a gauge factor of 5.75 * 105 at 100% strain in a stretchable transistor. The blend film is also highly stretchable (fracture strain, >1300%) and autonomously self-healable at room temperature. We proceed to demonstrate a fully integrated 5 * 5 stretchable active-matrix transistor sensor array capable of detecting strain distribution through surface deformation.
View details for DOI 10.1126/sciadv.aav3097
View details for PubMedID 31723597
- An Intrinsically Stretchable High-Performance Polymer Semiconductor with Low Crystallinity ADVANCED FUNCTIONAL MATERIALS 2019
- An Ultrastretchable and Self-Healable Nanocomposite Conductor Enabled by Autonomously Percolative Electrical Pathways ACS NANO 2019; 13 (6): 6531–39
- Polyimide-PEG Segmented Block Copolymer Membranes with High Proton Conductivity by Improving Bicontinuous Nanostructure of Ionic Liquid-Doped Films MACROMOLECULAR CHEMISTRY AND PHYSICS 2019; 220 (9)
- Modular and Reconfigurable Stretchable Electronic Systems ADVANCED MATERIALS TECHNOLOGIES 2019; 4 (3)
Electronic Skin: Recent Progress and Future Prospects for Skin-Attachable Devices for Health Monitoring, Robotics, and Prosthetics.
Advanced materials (Deerfield Beach, Fla.)
Recent progress in electronic skin or e-skin research is broadly reviewed, focusing on technologies needed in three main applications: skin-attachable electronics, robotics, and prosthetics. First, since e-skin will be exposed to prolonged stresses of various kinds and needs to be conformally adhered to irregularly shaped surfaces, materials with intrinsic stretchability and self-healing properties are of great importance. Second, tactile sensing capability such as the detection of pressure, strain, slip, force vector, and temperature are important for health monitoring in skin attachable devices, and to enable object manipulation and detection of surrounding environment for robotics and prosthetics. For skin attachable devices, chemical and electrophysiological sensing and wireless signal communication are of high significance to fully gauge the state of health of users and to ensure user comfort. For robotics and prosthetics, large-area integration on 3D surfaces in a facile and scalable manner is critical. Furthermore, new signal processing strategies using neuromorphic devices are needed to efficiently process tactile information in a parallel and low power manner. For prosthetics, neural interfacing electrodes are of high importance. These topics are discussed, focusing on progress, current challenges, and future prospects.
View details for DOI 10.1002/adma.201904765
View details for PubMedID 31538370
Conjugated Carbon Cyclic Nanorings as Additives for Intrinsically Stretchable Semiconducting Polymers.
Advanced materials (Deerfield Beach, Fla.)
Molecular additives are often used to enhance dynamic motion of polymeric chains, which subsequently alter the functional and physical properties of polymers. However, controlling the chain dynamics of semiconducting polymer thin films and understanding the fundamental mechanisms of such changes is a new area of research. Here, cycloparaphenylenes (CPPs) are used as conjugated molecular additives to tune the dynamic behaviors of diketopyrrolopyrrole-based (DPP-based) semiconducting polymers. It is observed that the addition of CPPs results in significant improvement in the stretchability of the DPP-based polymers without adversely affecting their mobility, which arises from the enhanced polymer dynamic motion and reduced long-range crystalline order. The polymer films retain their fiber-like morphology and short-range ordered aggregates, which leads to high mobility. Fully stretchable transistors are subsequently fabricated using CPP/semiconductor composites as active layers. These composites are observed to maintain high mobilities when strained and after repeated applied strains. Interestingly, CPPs are also observed to improve the contact resistance and charge transport of the fully stretchable transistors. ln summary, these results collectively indicate that controlling the dynamic motion of polymer semiconductors is proved to be an effective way to improve their stretchability.
View details for DOI 10.1002/adma.201903912
View details for PubMedID 31489716
- An integrated self-healable electronic skin system fabricated via dynamic reconstruction of a nanostructured conducting network NATURE NANOTECHNOLOGY 2018; 13 (11): 1057-+
- Effect of Nonconjugated Spacers on Mechanical Properties of Semiconducting Polymers for Stretchable Transistors ADVANCED FUNCTIONAL MATERIALS 2018; 28 (43)
- Nonhalogenated Solvent Processable and Printable High-Performance Polymer Semiconductor Enabled by Isomeric Nonconjugated Flexible Linkers MACROMOLECULES 2018; 51 (13): 4976–85
Tough and Water-Insensitive Self-Healing Elastomer for Robust Electronic Skin
2018; 30 (13): e1706846
An electronic (e-) skin is expected to experience significant wear and tear over time. Therefore, self-healing stretchable materials that are simultaneously soft and with high fracture energy, that is high tolerance of damage or small cracks without propagating, are essential requirements for the realization of robust e-skin. However, previously reported elastomers and especially self-healing polymers are mostly viscoelastic and lack high mechanical toughness. Here, a new class of polymeric material crosslinked through rationally designed multistrength hydrogen bonding interactions is reported. The resultant supramolecular network in polymer film realizes exceptional mechanical properties such as notch-insensitive high stretchability (1200%), high toughness of 12 000 J m-2 , and autonomous self-healing even in artificial sweat. The tough self-healing materials enable the wafer-scale fabrication of robust and stretchable self-healing e-skin devices, which will provide new directions for future soft robotics and skin prosthetics.
View details for PubMedID 29424026
- Taming Charge Transport in Semiconducting Polymers with Branched Alkyl Side Chains ADVANCED FUNCTIONAL MATERIALS 2017; 27 (34)
- Phase transition of block copolymer/homopolymer binary blends under 2D confinement MACROMOLECULAR RESEARCH 2017; 25 (6): 656–61