Much of our work is motivated by the fundamental challenge and the growing need of in advanced manufacturing (e.g. "grend "smart" materials and processes, additive manufacture or 3D printing). One focus of our research has been the exploration of the adhesion, surface forces, and associated micro-mechanical properties of soft materials including both synthetic and biological polymers, sticky fluids (e.g. , adhesives, pastes, inks and lubricants), and biological tissues under micro- and confinements. In addition to generating knowledge and making new discoveries, our research program aims to explore practical applications for responsive and "smart" devices by combining novel micro- and nano-fabrication, and surface engineering techniques with an approach. In other words, we learn engineering principles from superior biological designs and tailor physical chemical properties of macromolecules and associated with phenomena such as wetting, deformation, cracking. Broadly speaking, the projects addressed by our research program fall into one or more of the following areas.
Biomimetic Adhesion and Bio-Inspired Materials
Our research is inspired by the amazing aptitude of some insects and lizards, such as geckos. They can stick readily and rapidly to almost any surface (whether it is hydrophilic or hydrophobic, rough or smooth, dry or wet) and readily detach with equal rapidity (i.e. tens of milliseconds). The development of novel adhesive materials is important for effective bonding of dissimilar material components, which is one of the most critical technical prerequisites for manufacturing biosensors, medical devices, microelectronics, etc.
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Micro and Nano Adhesion and Adhesives Technology
There have been strong demands for developing polymer-based conductive adhesives that can effectively join similar or dissimilar materials components. Compared to the soldering technology, adhesive joining offers numerous advantages including mild processing conditions, simplified processing steps (reducing process cost), and ultrafine pitch capability. By applying various conductivity-enhancing agents and controlling mixing process, we aim to formulate new products with high electrical conductivity, good mechanical strength, and desirable printability.
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Nanoparticles Synthesis/Functionalization and Dispersion in Nanocomposites
We also synthesize new nanoparticles with various shapes and intrinsic properties, and study the dispersion and enhanced properties of nanofiller/polymer composites. The size, shape and loading concentrations of nanofillers are being investigated to understand their effects on the energy transfer processes, the contact adhesion, the surface morphology, the tribological properties, and the final electrical and thermal conductivities of the composites. We aim to generate new knowledge and produce new nanocomposites, which are much-needed information and of great importance in the field.
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Polymers, Interfacial Phenomena and Surface Chemistry
We have also been developing advanced materials to solve practical problems. For example, we studied the relationship between the oleophobicity of micropatternedtrichloroperfluorooctylsilane (FDTS)-blended PDMS elastomer surfaces and the reduction of oil adhesion at low temperatures. In addition, we also fabricated electrically conductive and superoleophobicpolydimethylsiloxane films by combining FDTS-blended PDMS elastomer with silver nanowires. This multifunctional material can remove the frozen oil droplets in a more effective way.
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- Oleophobicity of Biomimetic Micropatterned Surface and Its Effect on the Adhesion of Frozen Oil
- Durable Microstructured Surfaces: Combining Electrical Conductivity with Superoleophobicity
Surface Forces and Contact Dynamics, Tribological Characterizations
We also conduct fundamental studies of the contacting surfaces in both static and dynamic conditions. In addition to essential macroscopic measurements, peel adhesion testing, shear and friction testing, and other detailed characterizations of surface wettability and micro- and nano-tribological properties are regularly performed. All these measurements are essential for their applications in coatings and adhesives industries. We also seek to understand the contact behaviors of nanoscopic thin films by designing new analytical solutions. Beyond this, new nanocomposites with superior tribological behaviors have also been developed.
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Contact Adhesion Studies of Hydrogels for Biomedical Applications
Hydrogels are a class of materials consisting of physical or chemical crosslinkage of hydrophilic polymer chains and a large amount of water. Hydrogels are similar in their physiochemical properties to the tissues in human body: hydrophilic, biocompatible, soft and adaptable to mechanical stress. In order to effectively transfer the hydrogels into practical applications as bioadhesive materials and artificial tissues (implants and repairs or reconstruction materials), it is important to understand the behavior of hydrogel under external stresses and to control the mechanical and surface properties of hydrogels. We elucidated the adhesion and associated micromechanical properties of hydrogels under various conditions.
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