Research Areas

Nature-inspired Water Management & Desalination

Desalination & Water management

Nature-inspired seawater desalination

Salt rejection of mangrove root
  • Mangroves are adapted to salt-stress in harsh coastal condition
  • Visualization of salt rejection at mangrove roots during 20 weeks

High salinity induces severe osmotic pressure difference across the cell membrane. However, mangrove species can survive in such harsh conditions. The roots of mangrove play an important role for rejecting salts without fouling.
Filtration of sodium ions using the nature-inspired membranes
Electrostatic interaction between root surface and salt ions allows the formation of ion depleted layer. High negative zeta-potential can serve high salt rejection, while water flux is consistent without fouling due to the macro-pores of the nature-inspired membrane.
Metal-organic framework (MOF) incorporated alginate/PVA beads allows efficient removal of dissolved ions with varied salt ion concentrations. During the adsorption process, both cations and anions are attracted to polymeric network through electrostatic and chemical reactions.

Brown algae-inspired recovery of lithium

Lithium adsorption of brown algae

Brown algae has a relatively large amount of lithium
Lithium adsorption mechanism of brown algae
Metal organic framework (MOF)-incorporated alginate hydrogel inspired by brown algae was fabricated for selective adsorption of lithium. Lithium selectivity is determined by the type of cross-linked metal ion as the basis of MOF growth.

Brown algae-inspired lithium recovery technologies

MOF-incorporated alginate beads exhibit a variety of amorphous structures with modulating lithium selectivity depending on the intertwinement degree of amorphous structure. As with the intertwinement, strong repulsive force of crosslinked Al3+ reject cations with a high adsorption affinity or lithium with a low adsorption affinity.
The incorporation of thermorespnosive polymer into alginate composite efficiently recovers lithium via thermal treatment without acidic treatment with a high lithium selectivity from Li-spiked seawater due to the strong repulsive force of crosslinked Al3+.

Solar-based water evaporation desalination and energy generation

Solar evaporation-based energy harvesting

A elastic and conductive polymer foam, which is called leaf-inspired energy-harvesting foam (LIEHF), containing polydimethylsiloxane with macro- and microporous structures homogeneously mixed with conductive carbon materials.
The LIEHF has excellent stability and sustains its electricity generation performance for 24 h. A bundle of proposed LIEHFs can generate sufficient power for operating commercial electronic devices.

Solar evaporation-based simultaneous fresh water and electricity generation

Polypyrrole-incorporated Al3+ or Zr4+ crosslinked alginate hydrogels rapidly evaporates seawater due to high photothermal conversion efficiency. Evaporation induces ion transport through hydrogel from bulk seawater to upper surface, while strong repulsive force of Al3+ or Zr4+ selectively rejects cations. Selective rejection induces a salinity gradient between hydrogel and bulk seawater. The evaporation-induced salinity gradient spontaneously generates electricity with producing freshwater. The practical application of scaled-up solar evaporator is also demonstrated under natural solar condition.

Plant Hydrodynamics and Biomimetics

Survival strategies of plants against cavitation in xylem vessels

Bubble formation due to water transport with negative pressure
Hydrodynamic mechanisms of structural strategies of vascular plants

Water harvesting of plants under extreme environments and biomimetic devices

How Tillandsia usneoides transports water efficiently ?
Domino-like water transport on Tillandsia via flexible trichome wings

Foliar uptake of PM particles through stomatal apertures

Foliar uptake of AuNPs through stomatal apertures of Perilla frutescens

Uptake of fluorescence in plant (garlic chive) leaves

Plant Hydrodynamics and Biomimetics

Embolism and water refilling in xylem vessels and embolism repair

Xylem sap transport under negative pressure
Embolism repair and active flow regulation
Stop-and-acceleration pattern in the xylem-inspired channel
As the meniscus reaches the porous mesh in the middle of the channel, it stops for 16 s and then restarts to advance toward the right side.
Three-steps of water-filling process at porous mesh
As the meniscus accelerates, pressure rapidly released to near the atmospheric pressure.
Stop-and-acceleration flow phenomena
As the meniscus meets the mesh, pressure difference across the mesh begins to accumulate. The water flow immediately penetrates the mesh and accelerates forwards as the pressure difference reaches the threshold value.

Water absorption inspired by cactus root

Structural and functional features of cactus root
Optical image of a Opuntia microdasys reveals the structural characteristics of the cactus roots, which are covered with rhizosheath composed of root hair, soil, and mucilage. Complicated structure of cactus enables the cactus to absorb large amount of water.
Water management abilities of CRIM
The CC (cryogel + cellulose fibers) model exhibits the highest evaporation ratio, followed by the CM CM (cryogel + microparticles) and CCM (cryogel + cellulose fibers + microparticles) models.
Schematic diagram of cactus root-inspired model (CRIM)
Through selective combination of cellulose fibers, microparticles, and agarose solution, three different presolutions for the CRIM models; CC (cryogel + cellulose fibers), CM (cryogel + microparticles), CCM (cryogel + cellulose fibers + microparticles) were prepared. The micron-scale cellulose fibers favorably absorb water within their complex fibrous structures.

Enhancement of leaf transpiration by surface acoustic wave (SAW)

Internal structures of a plant leaf and SAW activation
When acoustic energy is transferred by SAW through the PDMS sheet, water molecules in the air spaces and veins in the mesophyll tissue are disturbed by the acoustic energy and evaporate quickly through the stomata.
Sequential images showing local delivery of dye solution in plant leaf
Leaf transpiration activated by SAW frequencies
Optimum SAW frequency for enhancing leaf transpiration is 15 MHz.
Measurement of the excitation lengths and areas
Excitation area is inversely proportional to the square of SAW frequency, and it reaches maximum at 10 MHz SAW due to leaky SAW waves and attenuation coefficient.

Wood-based solar-driven desalination

Improved water transport by removing lignin of a balsa wood
Comparison of evaporation rates according to lignin removal ratio

Waste biomass-based solar absorber for solar-driven desalination and water treatment

Bamboo-based solar absorber for seawater desalination
Peanut shell-derived photothermal absorber for solar desalination
Solar absorbers made of carbonized bamboo and waste peanut shell for solar desalination

Hydrogel & aerogel based interfacial solar steam generation (ISSG) for desalination

Functionalization of porous polymer network
  • Functionalized polymers are utilized for ISSG
  • Thermo-responsive properties, bilayered lamination, or ionic polymeric constituents are utilized
Three-dimensional ISSG structures
  • Evaporation behaviors are studied with changing aspect ratio, porosity, thermal properties of solar absorbers
3D ISSG evaporators with convective flow
Anti-salt property of solar absorbers

Seawater Desalination Ion-adsorptive MOF adsorbents of seawater to reduce salt concentration

MOF-incorporated alginate/PVA adsorbent
  • Metal-organic framework (MOF) is utilized to capture salt ions from seawater to decrease salinity
  • Alginate/PVA based double networks stably adsorb salts
Three-dimensional ISSG structures
  • Many parameters are investigated to enhance ion removal rate and stability of desalination system
3Hybrid seawater desalination experiment
  • Beads-type adsorbents can be applied into another desalination techniques, such as membrane filtration, etc.
특허 정보 등록번호: 1023324340000 / 출원번호: 1020200127214

Porous carbon-based 3D steam generator for photothermal-based solar desalination

Using advanced porous carbon materials solar evaporator maximizes heat absorption and steam generation.
This kind of research offers a promising pathway, integration of solar energy and innovative materials to resolve global water scarcity.