Vertically aligned carbon nanotube (CNT) arrays are promising candidates for advanced thermal interface materials (TIMs) since they possess high mechanical compliance and high intrinsic thermal conductivity. Some of the previous works indicate that the CNT arrays in direct dry contact with the target surface possess low contact thermal conductance, which is the dominant thermal resistance. Using a phase sensitive transient thermo-reflectance (PSTTR) technique, we measure the thermal conductance between CNT arrays and copper (Cu) surfaces under different pressures. The experiments demonstrated that the contact force is one of the crucial factors for optimizing the thermal performance of CNT array-based TIMs. The experimental results suggest that the Cu-CNT arrays’ contact thermal conductance has a strong dependence on the surface deformation and has an order of magnitude rise as the contact pressure increases from 0.05 to 0.15 MPa. However, further increase of the contact pressure beyond 0.15 MPa has little effect on the contact thermal resistance. This work could provide guidelines to determine the minimum requirement of packaging pressure on CNT TIMs.

Passive radiative cooling technology serves as an energy-free alternative to traditional cooling systems. Porous polymer structures are frequently employed for radiative cooling by leveraging the refractive index mismatch between the polymer and the pores, enabling the scattering of incoming sunlight. Recently, water-soluble and readily available Sodium chloride (NaCl) particles have been utilized as sacrificial templates for sustainable pore creation. Nevertheless, optimizing NaCl particle size, and thus the polymer pore size to enhance scattering capabilities remains a challenge. Here, we report a simple, scalable, and sustainable approach to creating an optimized porous polydimethylsiloxane (PDMS) film. This approach utilizes ultrafine NaCl powders as sacrificial templates, which were synthesized via ultrasonic precipitation to ensure their small size. The ultrafine NaCl particles have a size distribution centered around 6-8 μm, and the as-fabricated porous PDMS film achieves a high thermal emissivity of 0.95 within the atmospheric window (8-13 μm) and exhibits a reflectivity of 0.95 within the visible range (0.4-0.78 μm). Due to the desired dual-spectrum properties, the porous PDMS film exhibits a superior subambient cooling capacity over that fabricated with typically larger NaCl particles under strong sunlight. This study offers a scalable and practical radiative cooling solution for sustainable thermal management.

A micropolarizer array (MPA) that can be integrated into a scientific camera is proposed as a real-time polarimeter that is capable of extracting the polarization parameters. The MPA is based on highly aligned carbon nanotube (CNT) films inspired by their typical anisotropy and selectivity for light propagation over a wide spectral range. The MPA contains a dual-tier CNT pixel plane with 0° and 45° orientations. The thickness of the dual-tier structure of the CNT-based MPA is limited to less than 2 μm with a pixel size of 7.45 μm × 7.45 μm. The degree of polarization of the CNT-MPA reached 93% at a 632 nm wavelength. The specific designs in structure and semiconductor fabrication procedures are described. Compared with customary MPAs, CNT-based MPA holds great potential in decreasing the cross-talk risk associated with lower film thickness and can be extended to a wide spectral range.

Super-aligned carbon nanotubes (CNTs) film has strong anisotropy to light propagation. In order to better integrate the self-assembled CNTs into microelectromechanical system (MEMS) for polarization applications, some inherent impacts on polarization properties of CNT film were investigated. We described the polarization effects of the film thickness variation in detail, giving an optimum thickness range which is around 700–800 nm. The amorphous carbon content of CNT film was reduced by oxidation process where the transmittance increased by almost 4 folds. The alignment of CNT arrangement was optimized from 0.41 (Chebyshev orientation parameter) to 0.54 by manipulating the C ₂ H ₄ flow rate from 54 to 80 sccm. More specifically, a sample possessing a degree of polarization up to 99% and transmittance over 45% was obtained through proper regulations. The validated optimization makes the aligned CNT films more feasible and valuable for the integration of the CNT polarimeters with MEMS technology.