OVERVIEW

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"Materials performance is governed by property and geometry."

My PhD research includes adhesives and films, based on kirigami techniques and knowledge of mechanics of soft materials. 

​Now, I am a Research Engineer in the chemical industry. I am not the smartest fellow to push the frontiers of knowledge by revealing a secretive nature of materials through complex measurements and theories, which I think is a primary role of Scientists in academia (Check out this page to learn model scientists and academic work that significantly influenced me).

​But I am capable of grasping perspectives of both experts and lay people, connecting dots of scattered information to find critical gaps, and communicating with people from different backgrounds to form a companionship. Throughout my professional career, my goal is to develop game-changing materials and technologies with collaborative teams, which make a significant impact on the world and lifestyle.

PROJECTS

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"Polydimethylsiloxane (PDMS) is a unique inorganic polymer."

Silicone polymers for extreme environments
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Silicones are expensive compared with other common polymers such as acrylics, polyurethanes, and hydrocarbon polymers. But they offer unique properties essential for high-end applications that others struggle to, for example, a high thermal stability. One of the most common commercially available silicones, polydimethylsiloxane (PDMS), can remain flexible from - 40 °C to 200 °C. This unique mechanical property and other numerous desirable properties are in general attributed to a very high bond energy of the siloxane (Si-O-Si) backbone and its virtually zero rotational energy, along with close-packed, low surface energy methyl groups around the backbone. The world is increasingly requiring materials that remain functional under extreme environments. Emerging markets such as electric vehicles (EV), high-speed telecommunications, and flexible electronics can benefit from silicones.  

"Cuts enhance adhesion."

Kirigami-inspired smart adhesives
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Adhesives are typically permanent and strong (e.g., epoxy adhesive) or reversible with limited strength (e.g., Post-it Note). However, emerging technologies such as wearable electronics, advanced healthcare, and recycling of electronic components require adhesives that overcome the trade-off and exhibit strong yet easy release properties. We have developed a new technique to create cut-based, strong yet easy-to-peel adhesives without tuning chemical compositions. This technique can be adopted to current technology such as die-cutting machine and is readily applicable to diverse standard adhesive materials (e.g., pressure sensitive adhesive), surfaces (wet and dry), and sizes (from nano- to meter-scale). In addition, this technique can be coupled with emerging technologies such as additive manufacturing (AM) and laser-based subtractive manufacturing, and machine learning (ML). to enable high throughput materials development (HTMD).

"Pressure rapidly switches adhesion."

Pneumatically controlled adhesives

Traditional vacuum grippers used in the packaging industry struggle with porous, irregular, or multiple discrete objects. To address the issue, we have developed adhesion-based grippers that rapidly pick up and release such objects through a pneumatic system. The gripper consists of an adhesive membrane and a compliant foundation. Each component takes turns controlling adhesion in each extreme case (i.e., high and low adhesion). When air is removed (ΔP < 0), the foundation becomes stiff and determines adhesion, resulting in high adhesion. In contrast, when air is injected (ΔP > 0), the non-sticky membrane determines adhesion, enabling easy release. This novel mechanism is demonstrated by picking and releasing common objects, rough and porous materials, and arrays of elements with a 14,000× range in mass by switching from high adhesion to low adhesion within 0.1 s.

"Cuts make materials readily deformable."

​Kirigami-based deformable composites

Deformable materials such as rubbers are critical for emerging stretchable electronics applications including bio-monitoring wearable sensors to enable comfort on one's skin during body motions over the extended use. Instead of the conventional approach to enabling deformability by uncoiling of entangled polymer chains, we have focused on patterning materials with visible cut structures as an alternative method to create deformable materials. This new approach has several advantages such as scalability from nano- to meter-scale, capability to make intrinsically rigid materials stretchable (e.g., ceramics and metals), and tunability of material properties without changing chemicals. 

"Mechanics of materials matters."

Mechanics of soft materials

Synthesized polymers are of little use without understanding how they behave when a force is applied. We have characterized adhesion of diverse soft gels (e.g., hydrogels) with modulus less than 100 kPa by using a normal adhesion test with a hemispherical-ended probe. Lately, beyond kirigami-based materials, I have been studying and developing cut-free, soft composites for various applications and topics such as heat management and programmed material failure, based on knowledge of fracture mechanics and mechanics of adhesion.