Department of Chemical and Biomolecular Engineering
Korea Advanced Institute of Science and Technology

About the Lab

Functional Thin Films Laboratory

Our research focuses on the fabrication of functional nano-coatings using chemical vapor deposited polymeric films. The anticipated applications include various electronic, energy, and biomedical device applications.



■ Initiated chemical vapor deposition (iCVD)
   iCVD process utilizes very simple machinery with low power consumption. Since the processes are performed at ambient temperature, the iCVD polymers are easily applicable to substrate materials vulnerable to liquid phase process and/or heat, such as paper, fabrics, and membranes, without damaging the substrates. Polymeric films can also be easily stacked with sharp interface, free of solvent-related problems. The functionality of polymeric coatings can be easily incorporated by introducing various kinds of monomers. There is a wide room for further device applications using chemical vapor deposited polymers. The iCVD coatings can act as an essential building block for various micro/nano device applications including MEMS/NEMS, stimuli-responsive drug delivery systems, and diverse kinds of bio-devices.

 

Scope of Research

■ Application 1 – Surface treatment via iCVD polymer films

 

   A robust superhydrophobic fabric is obtained by introducing iCVD deposited polymer film. The hierarchical structure of the fabric surface is simply achieved by controlling the operation parameter of iCVD process. The robust superhydrophobic fabric displays superhydrophobicity and chemical and mechanical robustness. A facile and reproducible fabrication method was developed to render the Janus property to arbitrary porous substrates. With a one-step vapor-phase deposition process, a conformal coating of hydrophobic PHFDMA polymer film was achieved on both faces of the porous substrate. By simply floating the PHFDMA coated substrates on KOH(aq) solution, only one face of substrate became hydrophilic. This method can be applied to various kinds of clothing such as pants and shirts, something that the lamination process for Goretex has not allowed.



■ Application 2 – Encapsulations & Barrier films

 

   Insulating layers based on oxides and nitrides provide high capacitance, low leakage, high breakdown field and resistance to electrical stresses when used in electronic devices based on rigid substrates. However, their typically high process temperatures and brittleness make it difficult to achieve similar performance in flexible or organic electronics. However, the iCVD polymers can be versatile polymeric insulating layers that meet a wide range of requirements for next-generation electronic devices. Highly uniform and pure ultrathin films with excellent insulating properties and flexibility can be fabricated via the iCVD process. The low process temperature, surface-growth character, and solvent-free nature of the iCVD process enable the iCVD film to be grown conformally on various plastic substrates to yield flexible field-effect transistors as well as on a variety of channel layers, including organics, oxides, and graphene.



■ Application 3 – Encapsulations & Barrier films

 

   Organic/inorganic hybrid multilayer for encapsulation of organic electronics can be fabricated using iCVD layer. The iCVD/ALD pair produces multilayer with excellent barrier and optical properties. The process is solely conducted in vapor phase and the process temperature is mild below 90°C so that the deposition is applicable on organic electronics.


 

  The iCVD polymer film can be used as a barrier film on the PDMS micromold blocking the penetration of oxygen and organic solvents. With this barrier film, we were able to synthesize monodisperse polymeric particles of size down to 3 μm, which has been reported to be extremely challenging with bare PDMS micromold. The polymeric barrier film on the PDMS micromold enabled this successful synthesis of microparticles by effectively blocking the diffusion of oxygen, which is a well-known radical quencher in radical polymerization, through the PDMS micromold. Therefore, the polymeric barrier film coated on PDMS micromold via iCVD process will broaden the application of PDMS to microfluidic area for the synthesis of smaller microparticles with various organic substances.



■ Application 4 – Biological application

  

   Bioactive, functional scaffolds are required to improve the regenerative potential of stem cells for tissue reconstruction and functional recovery of damaged tissues. Here, we report a paper-based bioactive scaffold platform for stem cell culture and transplantation for bone reconstruction. The paper scaffolds are surface-engineered by an initiated chemical vapor deposition process for serial coating of a water-repellent and cell-adhesive polymer film, which ensures the long-term stability in cell culture medium and induces efficient cell attachment. The prepared paper scaffolds are compatible with general stem cell culture and manipulation techniques. An optimal paper type is found to provide structural, physical, and mechanical cues to enhance the osteogenic differentiation of human adipose-derived stem cells (hADSCs). A bioactive paper scaffold significantly enhances in vivo bone regeneration of hADSCs in a critical-sized calvarial bone defect. Stacking the paper scaffolds with osteogenically differentiated hADSCs and human endothelial cells resulted in vascularized bone formation in vivo. Our study suggests that paper possesses great potential as a bioactive, functional, and cost-effective scaffold platform for stem cell-mediated bone tissue engineering. To the best of our knowledge, this is the first study reporting the feasibility of a paper material for stem cell application to repair tissue defects.



■ Application 5 – Nano-adhesive & Microfluidics

  

   Microfluidic devices have many potential applications including integrated analytical systems, biomedical devices, high throughput screening, and studies of chemical and biochemical reactions. A sub-100nm thick nano-adhesive was developed using epoxy-functional iCVD coatings. This adhesive dramatically enhanced adhesion between various substrates, potentially allowing introduction of various kinds of substrates into microfluidic device fabrication. With proper selection of materials for substrate, it is anticipated that fabrication of microfluidic devices compatible with various organic solvent will be feasible. This feature enables a variety of chemical reactions in microfluidic devices. Moreover, the adhesion between the substrates can dramatically increase the throughput of microfluidic devices permitting their operation in turbulent regime.





 

Sung Gap Im (임성갑)
Assistant Professor


Office Phone: +82-42-350-3936
Fax: +82-42-350-3910
E-mail: sgim@kaist.ac.kr
Homepage: http://ftfl.kaist.ac.kr/

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