strength as high as 3.8-6.94 GPa. [ 6,11 ] In the production of light-weight and ultrastrong CNT fi lms, a solvent could play crucial roles in densifying the CNT assemblies, [ 7,12 ] in acting as a carrier to infi ltrate polymeric compounds, [ 6 ] and in providing suffi cient plasticity to the fi lm for possible stretching treatments. [ 7,11 ] Particularly, the solvent's polarity had been proved to be more important than its volatility in the densifi cation process. [ 12 ] The 2D CNT fi lm is formed by numerous bundles of CNTs, and each bundle contains tens of individual CNTs. Considering this hierarchical feature of CNT assemblies, it is useful to defi ne different structural parameters at different scales to describe the assembly structure. For example, the overall porosity [ 13 ] or CNT volume fraction, [ 14,15 ] alignment level from polarized Raman spectroscopy, [ 4,16 ] alignment described with Herman's orientation factor, [ 16,17 ] and CNT aggregation level [ 11 ] have been used by different research groups. As the solvent treatments are important to optimize the CNT assembly structure based on densifi cation effect [ 12 ] and lubricationinduced alignment, [ 7 ] it is also necessary to investigate whether there could be different effects on the assembly structure at the microscale caused by the differences in the solvent's polarity, volatility, surface tension, or viscosity. [ 12 ] In this paper, we report another important role of solvent, namely the volatility-induced networking effect, to induce different interior microstructures inside the CNT fi lm and thus tunable stretchability for the fi lm. High volatile solvents usually cause the CNTs to form a fi shing net-like network structure. The higher the volatility, the larger the mesh size. Such network postpones the fracture threshold of tensile strain, leading to improved stretchability. Afterall, it is the polarity that determines the level of densifi cation and thus the fi lm's elastic modulus. For the pure CNT fi lm obtained by acetone densifi cation and networking, the modulus, strength, and fracture strain were 2.32 GPa, 121 GPa, and 2.5%, respectively, all remarkably higher than those obtained by using ethanol densifi cation (1.91 GPa, 130 GPa, and 1.8%). Even when the solvent treatment was applied under a tension on the fi lm, acetone still showed higher ability to improve the strength (up to 3.19 GPa) and fracture strain (4.6%) than ethanol. This phenomenon can also be utilized to guide the design and fabrication of other nanocarbonbased structures. Solvent wetting is an effi cient way to densify carbon nanotube (CNT) assembly structures. Besides the polarity that determines the densifi cation level, the solvent's volatility is found to affect the assembly structure at the micrometer scale. A high volatile solvent like acetone can cause CNTs to simultaneously establish close contact at many intersecting points, and thus creates a strong network structure. This networking ability results in high plasticity for the resulting CNT assembly fi lms. O...