Research

WE FOCUS ON

Our research interests center on various areas of colloids, surface chemistry and materials science.

Colloidal Particles at Interfaces

Design and study the particle behaviour at the oil/water and air/water interfaces through combination of colloid science, polymer chemistry and soft matter physics.

Colloidal Particles at Interfaces

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Development of orthopaedic implant materials

Fabricate functional materials on Mg-based orthopaedic implants to meet specific clinical requirement
 
 

Development of orthopaedic implant materials

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Manufacturing of green packaging materials

Manufacture of green packaging materials for replacing single-use plastics
 
 
 

Manufacturing of green packaging materials

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Measuring the interactions between particle-particle and particle-surface

Measure the interactions between particle-particle and particle-surface using self-constructed total internal reflection microscopy (TIRM).

Measuring the interactions between particle-particle and particle-surface

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Studying micro-rheology with TIRM and magnetic tweezers

Explore the complex microscale viscoelastic properties of macromolecular network, soft matter and living cytoplasm.

Studying micro-rheology with TIRM and magnetic tweezers

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1. Colloidal Particles at Interfaces

The self-assembly of colloidal particles differing in size, shape and chemistry at a range of interfaces presents currently a very important impact in both academia and industry. On the fundamental side, particles trapped at oil/water or air/water interfaces offer researcher a quasi-two-dimensional system to directly investigate many fundamental problems in condensed matter physics such as low-dimensional phase transitions, jamming transitions and crystal melting, in which the particles can be viewed as large atoms and their trajectories can be used to elucidate the interactions, thermodynamics, and dynamics in those distinctive phases. On the practical side, particle-laden interfaces open many opportunities for modulating the assembly of particles and for the chemical modification of particles, which in turn allows its exploitation to the fabrication of novel materials, such as Pickering emulsions, foams, liquid marbles and colloidosomes. Currently our group is interesting in:

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Measuring the Interactions and Dynamics of Colloidal particles at Interfaces

Scientific report., 2014, 4, 4778 & langmuir, 2016, 32, 4909

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Particle Adsorption at Interfaces

Soft Matter 2013, 9, 9939 & 2014, 10, 6182

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Particle Assembly & Packing at the Curved Surface

ACS Applied Materials & Interfaces 2020, 12, 4989 & Chemical Communications, 2020, 56, 14011.

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Pickering emulsions in encapsulation, protection and controlled release

Current Opinion in Colloid & Interface Science 2020, 49, 1 & Langmuir, 2019, 35, 4205.

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Chemical and enzymatical catalysis at the interfaces

Chemical Science 2020, 11, 3797 & 2021, 12, 3885.

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Fabrication and application of Pickering foams

Journal of Colloid and Interface Science 2020, 579, 628.

2. Measuring the interactions between particle-particle and particle-surface

Non-covalent intermolecular forces, such as van der Waals, electrostatic, steric, and hydrophobic interactions, have played essential roles in determining the association, aggregation, adhesion and sedimentation processes of colloidal particles, surfactant micelles, and macromolecules, in solutions and biological systems. These interaction forces, however, are normally weak (<pN) and are challenging and difficult to be directly measured by common force techniques. In recent years, our group has successfully developed a Total Internal Reflection Microscope (TIRM), which has no commercially available equivalent, and employed it in a series of experiments to study how particle-surface interactions are affected by factors such as chemical surface modification, adsorbed nanoparticle and polymer layers, and surface morphology.

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TIRM at CUHK

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Interactions between particle-surface mediated by adsorbed polymers

Langmuir 2013, 29, 11038

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Measurment of particle-surface interactions in both equilibirm and nonequilibirum systems

Langmuir, 2019, 35, 8910.

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Interactions between protein-coated particle and polymer brushes in aqueous solution

Langmuir, 2018, 34, 8798.

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Interactions between protein-coated particle and polymer brushes in a serum environment

Colloids and Surface B: Biointerfaces, 2017, 150, 279.

3. Study the complex microscale viscoelastic properties of macromolecular network, soft matter and living cytoplasm

We have established a setup that enables the study of the micro-rheological properties and structure of materials near a flat surface. The basic idea is to combine the spatial resolution of total internal reflection microscopy (TIRM) with a magnetic tweezers. In a standard TIRM measurement, an evanescent wave is generated by the total internal reflection of an incident laser light at a solid (glass slide)/liquid interface. The light intensity of such a wave decays exponentially with the distance away from the interface. When a micrometer scale magnetic particle probe is placed within 100 nm of the interface, it probes all the particle-surface separations that TIRM can resolve. As a result, TIRM is a highly sensitive spatial detector for tracking the vertical motion of the embedded probe particle, and viscoelastic moduli can be quantitatively determined from the effect of confinement. The motion of the embedded probe particle can be controlled by a magnetic driving force, produced by two sets of four electromagnetic pole pieces symmetrically arranged in the upper and lower planes of the sample cell so as to achieve a three-dimensional position control. High precision of the magnetic force, at pN scale, can be achieved by real-time control of the electric current. We are therefore able to oscillate the embedded magnetic particle and monitor the response to infer network viscoelasticity by a combination of the magnetic tweezers and the evanescent wave-scattered particle tracking near a surface. We expect that this technique will have great potential for non-invasive and spatially resolved characterization of the micro-rheological properties of soft materials and living cells.

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TIRM + Magnetic Tweezers at CUHK

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Probing sol-gel transition of star polymers near overlap concentration

Macromolecules, 2019, 52, 8956.

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Monitoring colloidal gel evolution near a surface

Soft Matter, 2021, 14, 9764.

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Probing microrhelogy of soft particles near a solid surface

Journal of Colloid and Interface Science, 2021, 597, 104.

4. Development of orthopaedic implant materials

Biocompatible and biodegradable magnesium (Mg) and its alloys possess excellent potential as orthopaedic implant biomaterials because they have similar mechanical properties to natural bones and magnesium ions (Mg++) are known to promote the growth of new bone. However, because Mg/Mg alloys corrode inside the human body, their mechanical properties deteriorate too quickly and lose their support functions if they are used for bone fracture fixation. Additionally, when the rate of corrosion-induced hydrogen generation is higher than the body’s natural hydrogen adsorption rate, hydrogen bubbles and alkalization can occur. As such, it is important to develop new biocompatible and corrosion-controlled bio-implants made of Mg and its alloys. Currently our group is interesting in:

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Poly(L-lactice acid) (PLLA) coatings on Mg substrates to control corrosion

ACS Applied Bio Materials, 2019, 2, 3843.

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Polymer composite coatings on Mg sbubstrate for corrosion protection adn cytocompatibility promotion

ACS Applied Bio Materials, 2020, 3, 1364.

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Development of Mg/Ti hybrid system for fracture fixation and healing enhancement at load-bearing skeletal site

Biomaterials, 2018, 180, 173.

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Injectable Mg-based foam scaffold for bone regeneration

5. Manufacturing of green packaging materials

Plastics, as most people refer to common polymers, are made from fossil fuels and have brought great convenience to our lives. We use plastic-based products in various fileds, such as food packaging, electronics, construction, and many other fileds, among which about 16 billion disposable coffee cups are consumed every year and half a billion plastic straws are discarded every day worldwide. However, most plastics are not degradable and common schemes including reducing, reusing, and recycling have been largely ineffecive. Most single-use plastics go directly into waste and then are dumped to landfill and into oceans, which has casued significant harm to environment and marine life. In the past decades, biodegradable plastics have been intensely investigated in academic environments with the perpetual optimism to remedy plastic pollution problem. Unfortunately, the commercial impact has been demonstrated to be minimal. Therefore, developing environmentally friendly and biodegradable alternatives to current plastics represents an emerging need for a sustainable future.

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