arXiv subjects

Yunsong Pang

Publications and source records attributed to Yunsong Pang.

3 recordsLinked to original sources

arXiv2023

Ultra-soft Thermal Diodes Enabled by Dual-Alkane-Based Phase Change Composites

Thermal diode, a type of device that allows heat to flow in one direction preferentially, can be employed in many thermal applications. However, if the mechanical compliance of the thermal diode is poor, which prevents its intimate contact with heat source or sink surfaces, the thermal rectification performance cannot be used to its full extent. In this work, we introduce a heterojunction thermal diode made of a phase change material (PCM) consisting of dual alkanes (hexadecane and paraffine wax) and polyurethane. The fabricated thermal diode exhibits an ultra soft mechanical feature, with a low elastic modulus of 0.4 KPa and larger than 300% elongation until failure: the best values reported to date for thermal diodes. The measured thermal rectification factor is as high as 1.42 that in line with the theoretical model prediction. Molecular dynamic simulations reveal that the thermal rectification mechanism of the PCM based thermal diode originates from the crystal-amorphous phase transition of the hexadecane terminal as the temperature bias flips. Therefore, the heat flow in the forward direction is greater than the flux in the reverse direction. A series of experiments and finite element analyses are employed to verify the feasibility of thermal diodes for applications. Our results demonstrate that the fabricated thermal diode can be potentially used in building envelop to help with temperature regulation and thus reduce energy consumption for space cooling or heating.

physics.app-ph↗

arXiv2019

Light-Guided Surface Plasmonic Bubble Movement via Contact Line De-Pinning by In-Situ Deposited Plasmonic Nanoparticle Heating

Precise spatio-temporal control of surface bubble movement can benefit a wide range of applications like high-throughput drug screening, combinatorial material development, microfluidic logic, colloidal and molecular assembly, etc. In this work, we demonstrate that surface bubbles on a solid surface are directed by a laser to move at high speeds (> 1.8 mm/s), and we elucidate the mechanism to be the de-pinning of the three-phase contact line (TPCL) by rapid plasmonic heating of nanoparticles (NPs) deposited in-situ during bubble movement. Based on our observations, we deduce a stick-slip mechanism based on asymmetric fore-aft plasmonic heating: local evaporation at the front TPCL due to plasmonic heating de-pins and extends the front TPCL, followed by the advancement of the trailing TPCL to resume a spherical bubble shape to minimize surface energy. The continuous TPCL drying during bubble movement also enables well-defined contact line deposition of NP clusters along the moving path. Our finding is beneficial to various microfluidics and pattern writing applications.

physics.app-ph↗

arXiv2016

How to Characterize Thermal Transport Capability of 2D Materials Fairly? - Sheet Thermal Conductance and the Choice of Thickness

Ever since the discovery of the record-high thermal conductivity of single layer graphene, thermal transport capability of monolayer 2D materials has been under constant spotlight. Since thermal conductivity is an intensive property for 3D materials and the thickness of 2D materials is not well defined, different definitions of thickness in literature have led to ambiguity towards predicting thermal conductivity values and thus in understanding the heat transfer capability of different monolayer 2D materials. We argue that if conventional definition of thermal conductivity should be used as the quantity to compare the heat transfer capability of various monolayer 2D materials, then the same thickness should be used. Alternatively, to circumvent the problem of ambiguous thickness completely, we also suggest that a "sheet thermal conductance" to be defined as an intensive 2D material property when characterizing the heat transfer capability of 2D materials. When converting literature thermal conductivity values of monolayer materials to this new property, some new features that were not displayed when using different thicknesses show up.

cond-mat.mtrl-sci↗