Van der Waals heterostructures, formed by stacking atomically thin layers of two-dimensional materials, exhibit unique thermal and mechanical properties due to their weak interlayer interactions and strong in-plane bonding. These heterostructures are critical for next-generation electronics, optoelectronics, and energy-efficient devices, where thermal management and structural integrity are key challenges. Understanding interfacial thermal resistance, anisotropic heat dissipation, and strain engineering is essential for optimizing their performance.

Interfacial thermal resistance, or Kapitza resistance, is a major bottleneck in heat dissipation across Van der Waals heterostructures. Unlike covalently bonded materials, the weak interlayer forces in these structures lead to significant phonon scattering at interfaces, reducing thermal conductance. Studies have shown that the thermal boundary conductance between graphene and hexagonal boron nitride (hBN) ranges from 20 to 60 MW/m²K, depending on layer alignment and interface quality. Misalignment or contamination at the interface further exacerbates this resistance, leading to localized heating and reduced device reliability. Techniques such as surface functionalization or inserting intermediate layers have been explored to mitigate this issue, but trade-offs between thermal conductance and electronic performance must be carefully considered.

Anisotropic heat dissipation is another defining characteristic of Van der Waals heterostructures. In-plane thermal conductivity is typically orders of magnitude higher than cross-plane conductivity due to the strong covalent bonding within layers and weak Van der Waals interactions between them. For example, graphene exhibits an in-plane thermal conductivity of approximately 2000-4000 W/mK, while its cross-plane conductivity is only about 5-10 W/mK. This anisotropy becomes more complex in heterostructures combining materials with disparate thermal properties, such as graphene-MoS₂ stacks, where interfacial mismatch and phonon mode mismatch further influence heat flow. Tailoring layer composition and stacking order can help engineer desired thermal pathways for specific applications, such as heat spreaders or thermal insulators.

Strain engineering plays a crucial role in modulating both thermal and mechanical properties of Van der Waals heterostructures. Applied strain alters phonon dispersion relations, affecting thermal conductivity. Uniaxial tensile strain of 1% in graphene can reduce its thermal conductivity by up to 20% due to increased phonon-phonon scattering. In heterostructures, strain can also modify interfacial adhesion and interlayer spacing, impacting heat transfer across layers. Compressive strain, for instance, may enhance interlayer coupling, reducing Kapitza resistance but potentially introducing defects that degrade mechanical stability. Precise control of strain through substrate engineering or external stimuli enables dynamic tuning of thermal and mechanical behavior.

Characterization of these properties requires advanced techniques capable of probing nanoscale phenomena. Raman thermometry is widely used to measure thermal conductivity and interfacial resistance in Van der Waals heterostructures. By monitoring the temperature-dependent shift of Raman peaks, local heating and heat dissipation can be mapped with high spatial resolution. For example, laser-induced heating combined with Raman spectroscopy has revealed interfacial thermal conductance values in graphene-hBN systems with an accuracy of ±5 MW/m²K. However, this method requires careful calibration and is sensitive to laser power and material absorption coefficients.

Nanoindentation provides insights into the mechanical stability of Van der Waals heterostructures under applied stress. By measuring force-displacement curves, elastic modulus and hardness can be extracted, revealing the influence of stacking sequence and interlayer adhesion. Studies on graphene-MoS₂ heterostructures have shown that the elastic modulus can range from 200 to 400 GPa, depending on layer number and orientation. Fracture toughness, another critical parameter, is influenced by interlayer sliding and defect distribution. Nanoindentation also allows investigation of fatigue behavior under cyclic loading, which is vital for assessing long-term reliability in flexible electronics.

The interplay between thermal and mechanical properties in Van der Waals heterostructures presents both challenges and opportunities. Poor thermal conductance can lead to localized hot spots, accelerating material degradation, while mechanical instability may cause delamination or cracking under thermal stress. However, the ability to engineer these properties through layer selection, stacking order, and strain offers a pathway to customized solutions. For instance, heterostructures combining high-thermal-conductivity graphene with mechanically robust hBN can achieve balanced performance for high-power devices.

Future advancements in this field will likely focus on improving interfacial thermal transport through novel coupling strategies and exploring new material combinations with complementary properties. Computational modeling, particularly molecular dynamics simulations, will play a key role in predicting optimal configurations and guiding experimental efforts. As device dimensions continue to shrink, understanding and controlling thermal and mechanical behavior at the nanoscale will be indispensable for realizing the full potential of Van der Waals heterostructures in advanced technologies.