Stretchable Transparent Conductive Films from Long Carbon Nanotube Metals

Abstract

Flexible transparent conductors are an enabling component for large-area flexible displays, wearable electronics, and implantable medical sensors that can wrap around and move with the body. However, conventional conductive materials decay quickly under tensile strain, posing a significant hurdle for functional flexible devices. Here, we show that high electrical conductivity, mechanical stretchability, and optical transparency can be simultaneously attained by compositing long metallic double-walled carbon nanotubes with a polydimethylsiloxane substrate. When stretched to 100% tensile strain, thin films incorporating these long nanotubes (≈3.2 µm on average) achieve a record high conductivity of 3316 S cm at 100% tensile strain and 85% optical transmittance, which is 194 times higher than that of short nanotube controls (≈0.8 µm on average). Moreover, the high conductivity can withstand more than 1000 repeated stretch-release cycles (switching between 100% and 0% strain) with a retention approaching 96%, whereas the short nanotube controls exhibit only 10%. Mechanistic studies reveal that long tubes can bridge the microscale gaps generated during stretching, thereby maintaining high electrical conductivity. When mounted on human joints, this elastic transparent conductor can accommodate large motions to provide stable, high current output. These results point to transparent conductors capable of attaining high electrical conductivity and optical transmittance under mechanical strain to allow large shape changes that may take place in the operation and use of flexible electronics.

Photolithographic Patterning of Organic Color‐Centers

“…194.3, Rice University) were suspended by 1 wt% sodium dodecyl sulfate (SDS, 99%, Sigma-Aldrich) in Nanopure water (18 MΩ) by ultrasonication (Misonix, 1/2 inch flat tip, 4 h in pulsed mode [10 s on and 2 s off, 36 W]). Impurities and bundles were separated from the surfactant-suspended nanotubes by ultracentrifugation using an Optima XE-90 ultracentrifuge (Beckman Coulter, SW41 Ti rotor, 30000 × g) [33] and decanting the top fraction for further processing. The (6,5)-SWCNTs were then separated from the heterogeneous suspension of metallic and semiconducting SWCNTs by a multicolumn gel chromatography procedure using columns of Sephacryl S-200 HR (GE Healthcare) with a method adapted from Liu et al [34] Thin films of (6,5)-SWCNTs on glass substrates for Raman characterization were fabricated using a previously described method by Ng et al, [35] in which a solution of (6,5)-SWCNTs was filtered over a nitrocellulose membrane (25 nm pore size; Millipore VSWP).…”

Recent Progress in Transparent Conductors Based on Nanomaterials: Advancements and Challenges

“…The size of the 1D nanomaterials, their length and diameter obtained during synthesis, and their quality and density all play a crucial role in the performance of TSCs (Figure 1b,c). 41,58–60…”

“…Another approach to improving the performance is by sorting out the better quality CNTs among synthesized CNTs. Wang et al enhanced the performance of CNT/PDMS TSC by sorting long and metallic CNTs among purchased CNTs using the density gradient ultracentrifugation method and the superacid–surfactant exchange method 60…”

Stretchable Transparent Conductors: from Micro/Macromechanics to Applications

“…Second, the sliding mechanics of CNT on substrate could be used to enhance stretchability of STCs by forming percolation networks with CNTs overlapping to each other. The percolation networks of CNTs was more obvious in long CNT tubes; an STC based on long CNT metals showed high conductivity of 3316 S cm −1 at 100% tensile strain and 85% optical transmittance . Moreover, surface modification to either CNTs or substrate can significantly increase the interfacial shear stress by changing van der Waals interaction to chemical bonding; this can also useful to increase elongation of CNTs and maintain integrity of the conducting network during stretching.…”