Research Highlights

Shape Memory Metamaterials

Shape-memory materials can be deformed and then recover their original shape when exposed to external stimuli such as heat, light, or magnetic fields. Our paper in Advanced Science demonstrates that a nano-architected graphene foam exhibits a shape-memory effect with ultrahigh specific energy dissipation. While metamaterials typically derive their properties from a combination of the intrinsic characteristics of their constituent materials and their designed architecture, we introduce a third factor: van der Waals interactions. The interplay of these three contributions leads to an extraordinary shape-memory behaviour, opening new possibilities for high-performance, architected materials.

Publications:

D. T. Ho*, U. Schwingenschlögl*, Shape Memory Graphene with Ultrahigh Specific Energy Dissipation, Advanced Science 12, e08910, 2025. [link]

Water Desalination 

Water scarcity is one of the world’s biggest challenges. Reverse osmosis (RO) membranes, usually made from polyamide, are widely used for water desalination, but they consume a lot of energy because higher salt rejection usually means lower water permeability. Designing materials with precise, tunable pore sizes remains a major challenge. Our research introduces nano-architected graphene foams as a new type of RO membrane. Using molecular dynamics simulations, we show that these materials can block salt completely while allowing water to flow several orders of magnitude faster than conventional polyamide membranes. This approach could pave the way for highly efficient, next-generation desalination technologies.

Publications:

A. S. Voronin, D. T. Ho, Udo Schwingenschlögl, Functionalized Carbon Honeycomb Membranes for Reverse Osmosis Water Desalination, Advanced Materials and Interfaces 10, 2300250 (2023). [link]

D. T. Ho, T. P. N. Nguyen, A. Jangir, U. Schwingenschlögl, Graphene foam membranes with tunable pore size for next-generation reverse osmosis water desalination, Nanoscale Horizons 8, 1082-1089 (2023). [link]

Graphene Origami

Origami is a traditional paper-folding art found in several cultures, including Japan, and it has inspired modern developments in science and technology. Graphene origami enables extraordinary nanoscale devices; however, fabricating graphene origami structures remains highly challenging. Using molecular dynamics simulations, we demonstrate that local surface functionalization can induce controlled folding, creating graphene origami with complex geometries. Graphene Miura origami exhibits remarkable properties, including a highly flexible and tunable negative Poisson’s ratio arising purely from its geometry, similar to paper Miura origami, as well as negative thermal expansion resulting from the interplay of geometry, graphene’s intrinsic properties, and size effects. Notably, this negative thermal expansion is not observed in the corresponding paper-based Miura origami.

Publications:

D. T. Ho, U. Schwingenschlögl, Designing graphene origami structures with a giant isotropic negative coefficient of thermal expansion, Extreme Mechanics Letters 47, 101357 (2021) [link]

D. T. Ho, S. Y. Kim, and  U. Schwingenschlögl, Graphene origami structures with superflexibility and highly tunable auxeticity, Physical Review B 102, 174106 (2020). [link]

D. T. Ho, H. S. Park, S. Y. Kim, and  U. Schwingenschlögl, Graphene origami with highly tunable coefficient of thermal expansion, ACS Nano  14, 8969–8974 (2020). [link]

D. T. Ho, V. H. Ho, V. Babar, S. Y. Kim, and  U. Schwingenschlögl, Complex three-dimensional graphene structures driven by surface functionalization, Nanoscale 12, 10172-10179 (2020). [link]

Negative Poisson's ratio materials (Auxetics)

Publications:

 V. H. Ho, D. T. Ho, W. H. Shin, S. Y. Kim, Auxeticity of monolayer, few-layer, vdW heterostructure and ribbon penta-graphene, Physical Chemistry Chemical Physics 25, 4528-4541 (2023). [link]

A. Jangir, D. T. Ho, U. Schwingenschlögl, Tuneable Poisson’s ratio of monolayer GeS and Ge2SSe, Extreme Mechanics Letters 56, 101838 (2022). [link]

A. Jangir, D. T. Ho, U. Schwingenschlögl, Comment on “Electrical Switch of Poisson’s Ratio in IV–VI Monolayers via Pseudophase Transitions”, The Journal of Physical Chemistry Letters 13, 3609–3610 (2022). [link]

V. H. Ho, D. T. Ho, C. T. Nguyen, S. Y. Kim, Negative out-of-plane Poisson's ratio of bilayer graphane, Nanotechnology 33, 255705 (2022) [link]

D. T. Ho, S. Y. Kim, and  U. Schwingenschlögl, Graphene origami structures with superflexibility and highly tunable auxeticity, Physical Review B 102, 174106 (2020). [link]

 D. T.  Ho†, C. T. Nguyen, S. Y. Kwon, S. Y. Kim, Auxeticity in metals and periodic metallic porous structures induced by elastic instabilities, Physica Status Solidi B 256, 1800122 (2019) (†: same contribution). [link]

D. T. Ho †, V. H. Ho†, H. S. Park, and S. Y. Kim, Negative in-plane Poisson’s ratio for single layer black phophorous, Physica Status Solidi B 254, 1700285 (2017) (†: same contribution). [link]

D. T. Ho, S.-Y. Kwon and S. Y. Kim. Metal [100] nanowires with negative Poisson’s ratio, Nature Scientific Reports 6, 27560 (2016). [link]

D. T. Ho, S-D. Park, S.-Y. Kwon, T.-S. Han and S. Y. Kim. Negative Poisson’s ratio in cubic bulk materials along principal directions, Physica Status Solidi B 253, 1288 (2016). [link]

V. H. Ho, D. T. Ho, S.-Y. Kwon, and S. Y. Kim, Negative Poisson’s ratio in periodic porous graphene structures, Physica Status Solidi B 253, 1303 (2016). [link]

D. T. Ho, H. K. Kim, S.-Y. Kwon and S. Y. Kim. Auxeticity of face-centered cubic metal (001) nanoplates, Physica Status Solidi B 252, 1492 (2015). [link]

D. T. Ho, S.-D. Park, S.-Y. Kwon, K.-B. Park and S. Y. Kim, Negative Poisson’s ratio in metal nanoplates, Nature Communications 5, 3255 (2014). [link]

Negative thermal expansion

Publications:

D. T. Ho, U. Schwingenschlögl, Designing graphene origami structures with a giant isotropic negative coefficient of thermal expansion, Extreme Mechanics Letters 47, 101357 (2021) [link]

D. T. Ho, H. S. Park, S. Y. Kim, and  U. Schwingenschlögl, Graphene origami with highly tunable coefficient of thermal expansion, ACS Nano  14, 8969–8974 (2020). [link]

D. T. Ho, H. S. Park, S.-Y. Kwon, and S. Y. Kim, Negative thermal expansion of ultra-thin metal nanowires: A Computational Study, Nano Letters 17, 5113-5118 (2017). [link

Material Elastic Instabilities

When a metal is subjected to mechanical loading, it initially responds elastically as long as the deformation is small. Failure typically occurs through plasticity, driven by the motion of pre-existing dislocations and/or the nucleation of new ones. However, we show that defect-free metallic structures, such as nanoplates and nanowires, which can be fabricated experimentally, can fail under mechanical loading not through plasticity, but through elastic instability. In this case, the material undergoes homogeneous deformation without dislocation initiation, and dislocations appear only after the elastic instability regime. Because failure is governed by elastic instability, the relevant strength is the ideal strength rather than the conventional yield strength. Interestingly, ideal strength is not a fixed material property; it depends strongly on geometry. For example, thin nanoplates exhibit a ‘smaller is weaker’ trend, whereas nanowires show the opposite ‘smaller is stronger’ trend. This elastic instability also affects fracture behaviour.

Publications:

H. Kim, D. T. Ho, and S. Y. Kim, Fracture behavior transition in (001) cracked metal nanoplate induced by the surface effect, The Journal of Physical Chemistry C 125, 4277–4283 (2021) [link]

D. T. Ho, S. Kim, S.-Y. Kwon, S. Y. Kim, Ideal strength of nanoscale materials induced by elastic instability, Mechanics of Materials 11, 103241 (2020). [link]

C. T. Nguyen †, D. T. Ho †, S. T. Choi, D.M. Chun, S.Y. Kim, Pattern transformation induced by elastic instability of metallic porous structures, Computational Materials Science 157, 17-24 (2019) (†: same contribution). [link]

D. T. Ho, S.-Y. Kwon, H. S. Park, and S. Y. Kim, Metal nanoplate: Smaller is weaker due to failure by elastic instability, Physical Review B 96, 184103 (2017). [link]

D. T. Ho, S.-D. Park, S.-Y. Kwon and S. Y. Kim. The effect of transverse loading on the ideal tensile strength of face-centered-cubic materials, Europhysics Letters 111, 26005 (2015). [link]

D. T. Ho, Y. T. Im, S.-Y. Kwon, Y. Y. Earmme, and S. Y. Kim. Mechanical failure mode of metal (001) nanowires: Global deformation versus local deformation, Nature Scientific Reports 5, 11050 (2015). [link]