Electrospinner: In situ one-sided modification of nanofiber membranes with calcium salts: unidirectional transport of sweat and efficient radiative cooling!

Background

Maintaining human thermal comfort is essential for basic human metabolism and effective thermal management. Generally, thermal management systems achieve thermal regulation of the human body under various conditions through the synergistic effects of radiation, evaporation, conduction, and convection. Passive radiative cooling materials spontaneously reflect sunlight to reduce energy absorption and transfer heat to outer space through atmospheric windows, and have great potential in improving thermal comfort. However, the radiative cooling materials reported so far are mainly concentrated on hydrophobic polymer film materials, which are not conducive to the transfer of sweat from the skin to the outside world, and inevitably inhibit the cooling effect in humid and hot environments, especially in complex environments with variable climates or dynamic humid and hot environments, which will cause sweat accumulation. Polylactic acid (PLA), a biocompatible and degradable polymer, has been explored for daytime passive radiative cooling, but its inherent infrared emissivity is too low. Achieving continuous and efficient passive cooling in different environments such as dry and humid environments is still a current challenge.

Recently, the team of Professor Tang Shaochun from Nanjing University and the team of Professor Xia Zhengcai from Huazhong University of Science and Technology published a research result entitled "Advanced Janus Membrane with Directional Sweat Transport and Integrated Passive Cooling for Personal Thermal and Moisture Management" in Advanced Fiber Materials. This work proposed to use the high infrared emissivity of calcium sulfite (CaSO3) itself to modify the single side of the PLA fiber membrane with CaSO3 nanoparticles, which not only improved the solar reflectivity (reaching 96.6%) and infrared emissivity (reaching 96.1%, 15% higher than PLA) of the PLA membrane on one side, but also improved the wettability of the single side, so that the asymmetric wettability Janus membrane has the ability to directional transmit sweat (unidirectional transmission index is as high as 945%), realizing the effective combination of inorganic nano-enhanced radiation cooling and sweat directional evaporation cooling, and showing excellent cooling effect in dry and wet states. This work provides a new way for the design and development of intelligent thermal management fiber membrane materials.

The main point of this paper

Figure 1 shows the steps of coating uniform polymer Nanofiber Membrane on PLCL nanofibers during the iCVD process, and the subsequent biomolecule fixation process. Among them: Figure 1 (a) shows that the monomer and initiator are introduced into the iCVD reaction chamber by gentle heating, the heating filament activates the initiator into free radicals, the monomer is polymerized on the PLCL Electrospun Nanofbers, and the biomolecule is fixed on the PLCL Electrospun Nanofbers using pPFMA active ester; Figure 1 (b) shows the surface morphology and root mean square roughness (RMS) of different polymers (including bare silicon wafers, pP4D1, pP8D1 and pPFMA) measured by atomic force microscopy (AFM); Figure 1 (c-d) shows the unique chemical bond characteristics of PFMA and DVB shown in the FTIR spectrum, and the XPS spectrum further confirms the presence of functional groups such as C-F, C-O, and C=O in the iCVD polymer Nanofiber Membrane.

From the XPS analysis results of Figure 2(a), it can be seen that IgG was successfully immobilized on the pPFMA surface; through the fluorescence intensity quantification of Figure 2(b), it was found that the fluorescence intensity on the surface of the pP4D1 copolymer was the highest, indicating that its biomolecule immobilization efficiency was the best; AFM and QCM-D techniques were used to demonstrate the immobilization efficiency and surface characteristics of IgG on different polymer Nanofiber Membranes, and the results are shown in Figure 2(c-d), confirming that the surface of the pP4D1 copolymer is conducive to the immobilization of biomolecules.

Figure 3 shows the physical properties of PLCL Electrospun Nanofibers and their polymer coatings. Through the SEM analysis of Figure 3(a), it was found that the average diameter of the fiber increased slightly after coating with pP4D1, while the diameter of the aligned PLCL/pP4D1 nanofibers after applying 90% strain decreased, indicating that neither the coating nor the strain treatment destroyed the structure of the Electrospun Nanofibers; in addition, it was shown that the non-aligned PLCL and PLCL/pP4D1 Electrospun Nanofibers were randomly oriented, while the aligned nanofibers showed specific directionality. From the mechanical properties analysis results in Figure 3(b), it can be seen that the iCVD-coated PLCL Electrospun Nanofbers maintain similar mechanical strength and flexibility as the original PLCL nanofibers, indicating that the effect on the mechanical properties is not significant. The above analysis results show that the iCVD technology can effectively promote surface functionalization while maintaining the physical structure and mechanical properties of PLCL Electrospun Nanofbers.

Through in vitro experiments, SH-SY5Y neuroblastoma cells and PC12 adrenal pheochromocytoma cells were subjected to biological reactions on differently treated PLCL Electrospun Nanofbers. The results are shown in Figure 4. It can be seen that compared with bare nanofibers with only physical adsorption of laminin, Electrospun Nanofbers coated with pP4D1 by iCVD and chemically fixed with laminin significantly enhanced cell adhesion and diffusion. Cells showed a larger diffusion area and extension along the fiber direction on these functionalized surfaces; and the directional elongation of cells was further promoted by controlling the arrangement of Electrospun Nanofbers, indicating the potential application of iCVD functionalized PLCL nanofibers in the field of neural tissue engineering, and surface functionalization can effectively promote cell interaction.

In summary, this work provides a new method to improve the properties of the Electrospun Nanofbers surface, making it more suitable for the culture of neural cells and tissue engineering applications. Creating a special coating that promotes cell adhesion and alignment on the surface of Electrospun Nanofbers by iCVD technology is of great significance for the development of new biomedical materials.

Electrospinning Nanofibers Article Source:

https://link.springer.com/article/10.1007/s42765-024-00444-2