A Novel Application of High-Voltage Electrostatic Flocking: Thermal Interface Materials for Thermal Management.

Thermal interface materials (TIMs) are soft and malleable materials that enhance heat transfer by filling gaps between electronic components and heat sinks. [11] Fillers with high aspect ratios show great potential in developing high-performance thermal management materials. [107, 108] Electrostatic flocking technology enables the construction of densely vertically aligned filler arrays on planar substrates. By filling the gaps between vertically arranged fillers with an elastomer matrix through the electrostatic flocking process, TIMs with excellent thermal conductivity and extremely low filler content can be prepared. [15-22, 109] These TIMs not only exhibit enhanced thermal conductivity but also maintain flexibility by incorporating elastomeric materials into graphene fibers (GFs) (Figure a) or aligned carbon fibers (CFs) (Figures 13b, c). Their low filler content further enhances this flexibility, making their performance superior to conventional products.

[15, 16, 19, 22] The high thermal conductivity and excellent elastic compliance at low GF content are primarily attributed to the highly aligned structure of GFs and their inherently low stiffness (Figure a). [15] Electrostatic flocking technology also supports the large-scale preparation of vertically aligned carbon fiber (VACF) scaffolds, as shown in Figures b and c. [22] The vertically aligned structures constructed via electrostatic flocking can also synergize with thermally conductive fillers such as aluminum particles [16] to significantly enhance the material's thermal conductivity. Li et al. [16] reported a vertically aligned carbon fiber/silicone rubber/aluminum particle (V-CF/Al/SR) composite prepared by electrostatic flocking for thermal management applications (Figure d). This V-CF/Al/SR composite exhibits high directional thermal conductivity while demonstrating excellent flexibility and elasticity (Figure e). [16] The research team used electrostatic flocking to prepare upright CF scaffolds, effectively constructing efficient heat conduction paths within the composite. Additionally, Li et al. filled the air channels with an aluminum/silicone resin paste, significantly enhancing the material's thermal conductivity through multilayer CF-Al-CF heat conduction paths (Figure f). [16] This process greatly improved the in-plane thermal conductivity of the material, with the V-CF/Al/SR composite achieving an in-plane thermal conductivity of 12.32 W/(m·K), representing outstanding performance.

[16] Beyond the aforementioned applications, electrostatic flocking technology has also been used for mussel cleaning on ship hull surfaces. This technology leverages the superhydrophobicity and microporous characteristics of flocked surfaces, where the pore size is smaller than the diameter of the distal grooves of mussel foot tips, effectively resisting mussel adhesion. [110] Furthermore, electrostatic flocking has been applied in the design of remora-inspired adhesive discs, capitalizing on its ability to enhance mechanical properties. [79] When used in heavy oil cleanup, its hydrophobic surface reduces oil diffusion resistance, while the strong capillary forces accelerate heavy oil adsorption. [78] Simultaneously, electrostatic layering technology can serve as a novel method for preparing composite foam hollow epoxy macrospheres. [27] Compared to traditional "ball-rolling methods," this process achieves higher fiber content and superior compressive strength. [27] Zhang et al. utilized the high porosity of flocked substrates for microalgae cultivation studies. [35] Additionally, this technology can mimic the hair structure on the body surface of silver ants, achieving passive radiative cooling through complex optical path design. [111, 112] Zhang's team used short-staple fibers to create radiative cooling surfaces via electrostatic flocking technology (Figure 13g).

a) Actual demonstration of the flexible properties of GF-TIM; reproduced with permission. [15] Copyright 2024, American Chemical Society.
b) Schematic diagram of electrostatic flocking device configuration; reproduced with permission. [22] Copyright 2014, Wiley-VCH Verlag GmbH & Co. KGaA.
c) Large-scale electrostatic flocking process for VACF scaffolds; reproduced with permission. [22] Copyright 2014, Wiley-VCH Verlag GmbH & Co. KGaA.
d) Schematic diagram of the preparation process for V-CF/Al/SR composites; reproduced with permission. [16] Copyright 2024, American Chemical Society.
e) Demonstration of the flexibility of V-CF/Al/SR composites wrapped around a glass rod; reproduced with permission. [16] Copyright 2024, American Chemical Society.
f) Schematic diagram of the thermal conduction mechanism of V-CF/Al/SR composites; reproduced with permission. [16] Copyright 2024, American Chemical Society.

Other Application Areas
g) Schematic diagram of the cooling principle of a short-staple fiber array. [112] Copyright 2025, American Chemical Society.

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