(4ds) Advanced Manufacturing of Functional Soft Matter for Environmental Sustainability and Energy-Efficiency

My research interests are to develop an advanced manufacturing platform to fabricate functional soft materials for environmental sustainability and energy efficiency. With the outcomes of this research, I aim to contribute significantly towards the soft matter physics and colloid and interface science community.

Specifically, I am interested in the following three thrusts:

1. Development of an advanced manufacturing platform to fabricate micro/nanostructured soft materials, which will be generated by engineering interfaces of complex fluids imposed under an external force such as flow-driven shear stress, Marangoni stress, and electrohydrodynamic stress, etc. I aim to optimize the structure of these soft materials for efficient mass transport or electrochemical reactions. I also plan to use these materials as substrates for catalytic reactors and batteries.

2. Formulation of functional coatings for capturing and releasing environmentally harmful substances on-demand (e.g., air pollution, radioactive materials, and heavy metals in the ocean). Specifically, I aim to make functional coatings that attract harmful substances and can also release them by changing the surrounding condition through tunable colloidal interactions. I plan to apply these coatings on buildings or ships to eliminate harmful substances in the air and ocean.

3. Design of new classes of multistable soft materials that switch their physical properties (e.g., color and rheology) when applying short and temporary external stimuli (e.g., electric field, magnetic field, and light). For this, I aim to understand the metastability of various soft matter, which will form the basis of energy-efficient devices.

Postdoctoral Projects:

"Understanding of flow-induced reorganization of amphiphiles at aqueous-liquid crystal interfaces" Under Prof. Nicholas L. Abbott, Smith School of Chemical & Biomolecular Engineering, Cornell University, 2019 – 2021

"Reconfiguration of nanofiber forest by reorganization of liquid crystals and its emergent electro-optic properties" Under Prof. Nicholas L. Abbott, Smith School of Chemical & Biomolecular Engineering, Cornell University, 2019 - 2021

"Liquid crystals for multistable optical devices" Under Prof. Nicholas L. Abbott, Smith School of Chemical & Biomolecular Engineering, Cornell University, 2020 - 2021

Ph.D. Dissertation:

"Design of Novel Functional Colloidal Suspensions and Gels by Interfacial Engineering of Multiphasic Systems" Under Prof. Orlin D. Velev, Department of Chemical and Biomolecular Engineering, NC State University 2013-2019

Successful Proposals:

• IGNITE: Research Acceleration funding, Cornell University; 2021; totaling $25,000

Research Experiences:

As a soft matter scientist, I have extensive experience working with soft materials, including liquid crystals, colloidal suspensions, emulsions, aerogels, hydrogels, elastomers, biomaterials, and structured engineering plastics (e.g., fibers and 2D sheets). Using these materials, I have successfully fabricated advanced functional materials by engineering their molecular/nano/microscale structure to tune their colloidal interactions and interfacial properties.

Under the guidance of Prof. Orlin D. Velev at NC State University, we developed a new class of scalable nanomanufacturing flatform to generate a plethora of different morphologies of high surface area polymeric materials. One of the notable polymeric materials I have made is a so-called "Soft Dendrimeric Colloid (SDC)," a particle decorated with a branched nanofiber corona. SDCs have superior rheology and adhesion properties. Additionally, I have synthesized a new class of polymeric nanosheets with interconnected mesoporous structures, which have applications in developing materials for energy storage and catalytic reactions.

As a second project during my Ph.D., I developed a new class of 3D printing ink using the concept of homocomposites. Unlike conventional ink formulations, which use inorganic reinforcements, homocomposite inks are composed of crosslinked polymer particles and non-crosslinked polymer precursors of the same material. The inks have suitable rheological properties for 3D printing, originating from capillary interactions and jamming phenomena between particles. Based on this concept, I demonstrated 3D printing of elastomers and hydrogels, which are challenging to print.

During my postdoc with Prof. Nicholas L. Abbott at Cornell University, we developed an experimental system to study the reorganization of amphiphiles at aqueous interfaces using liquid crystals that unmasks various non-equilibrium interfacial phenomena of amphiphiles (i.e., adsorption, desorption, and interfacial mobility). Additionally, I have fabricated nanofiber forests in liquid crystals using chemical vapor deposition and explored their electro-optic response, which reflects shared strain between nanofibers and liquid crystals. I have also invented a new liquid crystal-based multistable material that exhibits multiple optical states, which can be used as the basis of energy-efficient optical devices.

Teaching Interests:

With my educational background in chemical engineering, I am prepared to teach core courses, including but not limited to thermodynamics, reaction engineering, transport phenomena. I am also ready to teach elective courses, including colloid and interface science, rheology, polymer physics, polymer chemistry, and nanotechnology. Given my research expertise, I am delighted to develop and teach advanced courses such as soft matter physics, adapted materials, and polymer composites.

Teaching and Mentorship Experiences:

During my Ph.D. and Postdoc, I have had the privilege of mentoring seven undergraduate, two Masters, and six Ph.D. students, including many from underrepresented or minority groups in STEM. These students are from various educational disciplines (i.e., biomedical engineering, chemical engineering, and materials science). Moreover, I served as a teaching assistant for three core chemical engineering classes at NC State University, including Reaction engineering, Thermodynamics, and Transport Processes. I have also served as a mentor for the senior design team at NC State University.

Notable Awards:

2020 2019 James K. Ferrell Outstanding Ph.D. Graduate Award (Honorable Mention), NC State University

2018 Best poster award, Soft Matter, NC, USA

2017 Finalist for 2017 Collegiate Inventors Competition, USPTO, VA, USA

Selected Publications:

• Sangchul Roh, Michael Tsuei, Nicholas L. Abbott, Using liquid crystals for in situ optical mapping of interfacial mobility and surfactant concentrations at flowing aqueous-oil interfaces, Langmuir, 37, 2021, 5810−5822.
• Austin H. Williams*, Sangchul Roh*(*Equal contribution), Alan R. Jacob, Simeon D. Stoyanov, Lilian Hsiao, and Orlin D. Velev, Printable homocomposite hydrogels with synergistically reinforced molecular-colloidal networks, Nature Communications, 12, 2021, 2834.
• Sangchul Roh, Austin H. Williams, Rachel S. Bang, Simeon D. Stoyanov and Orlin D. Velev, Soft dendritic microparticles with unusual adhesion and structuring properties, Nature Materials, 18, 2019, 1315−1320.
• Sangchul Roh, Lilian B. Okello, Nuran Golbasi, Jameson P. Hankwitz, Jessica A.-C. Liu, Joseph B. Tracy, and Orlin D. Velev, 3D printed soft magnetoactive capillary architectures with multidirectional shape reconfiguration, Advanced Materials Technologies, 4, 2019, 1800528.
• Sangchul Roh and Orlin D. Velev, Nanomaterials Fabrication by Interfacial Templating and Capillary Engineering in Multiphasic Liquids, AIChE Journal, 64, 2018, 3558−3564
• Sangchul Roh, Dishit P. Parekh, Bhuvnesh Bharti, Simeon D. Stoyanov and Orlin D. Velev, 3D Printing by Multiphase Silicone/Water Capillary Inks. Advanced Materials, 29, 2017, 1701554.

Intellectual properties:

• Orlin D. Velev, Sangchul Roh, 3D printing with silicone elastomer via capillary bridging of PDMS microbeads into thixotropic gel, Patent application, NCSU, 2017
• Orlin D. Velev, Sangchul Roh, Fractal-like particles, Patent application, NCSU, 2017