Tst350

Tensile Testing was carried out on a Linkam TST-350 without closing the stress-strain chamber and by using a displacement ramp of 5 mm min⁻¹. The shown values of stress were calculated by considering the constant cross-section area of the specimen’s mid-point at 0% strain. Absorption spectra were measured in transmission with a Flame-S UV-vis spectrometer from Ocean Optics. The spectra were smoothed via Savitzky-Golay filter considering 51 pts (6a) and 21 pts (6b). Excitation for photoluminescence (PL) spectra was carried out using a UV LED (Nichia NVSU233A UV SMD-LED, 365 nm, max. 1030 mW, operated with 900 mA) at a distance of 10 cm. The angle between exciting and detected light was 60 degrees. PL spectra were measured on the same spectrometer used for UV-vis spectroscopy and smoothed via Savitzky-Golay filter considering 21 pts. The data of optical properties and mechanical analysis was correlated via measuring time and include a maximum error in the strain of ±2%.

The tensile performance of the CNTYs was tested on a tensile tester (TST350, Linkam) at a gauge length of 10 mm and strain rate of 3 mm min⁻¹. The linear density of the given CNTY was determined by measuring the weight of 15 m of CNT yarn. In situ Raman analysis was carried out while the CNTY was strained with a gauge length of 30 mm on a tensile stage set on the sample stage of the Raman spectroscope. The CNT nanostructure was examined by field‐emission transmission electron microscopy (FETEM, JEM‐3000F, JEOL, Japan) and Raman spectroscopy (RAMANplus, Nanophoton) with a 532 nm laser. The purity of the CNTs was determined by thermogravimetric analysis (TGA; SDT‐Q600, TA Instruments) in air. The cross‐ and longitudinal sections of the CNTYs were characterized by field‐emission scanning electron microscopy (FESEM, SUPRA 55VP, Carl Zeiss, Germany) after cutting with a focused ion beam (FIB; Helios 650, FEI).

In situ X-ray diffraction measurements were performed at the Shanghai Synchrotron Radiation Facility (SSRF) with a radiation wavelength of 0.124 nm. A MAR CCD detector in the beamline BL14B1 with a resolution of 2048 × 2048 pixels was used to collect diffraction patterns. The distances of 187.2 and 1893.5 mm were used in the sample to detect space for wide-angle X-ray diffraction (WAXD) and small angle X-ray scatting (SAXS), respectively. All of the X-ray images were corrected for background scattering. Fit2D software was used to convert the two-dimensional (2D) X-ray patterns into one-dimensional (1D) curves.
Two procedures were used in X-ray diffractions measurements. The procedure under the stretching field: The stretching field was chosen to detect in situ microstructure evolution. Using the stretching speed of 20 μm/s in the Linkam TST350 (Houston, TX, USA) stretch stage, each exposure time was 20 s for both WAXD and SAXS measurements. The procedure under the temperature field: the film (thickness of about 1 mm) was wrapped with aluminum foil and isothermal for 5 min at 300 °C to eliminate thermal history; then, the film was cooled down to room temperature. The WAXD data were collected during the second heating process from room temperature to 300 °C in steps of 2 °C.

DNA (Deoxyribonucleic acid sodium salt from salmon testes, Sigma Aldrich) was dissolved in deionised water at 25 mg/ml without further purification. Pristine silicon, micropost-patterned silicon, or glass substrates were rinsed with acetone, ethanol and deionised water and then treated with O₂ plasma for 5 min to eliminate any organic/inorganic impurities.
For the doctor blade experiment, micropost-patterned silicon and glass substrates were sandwiched with a gap using an aluminium foil of 40 μm thickness. The DNA solution was injected into the sandwich cell by capillary forces, and then the upper glass piece of the sandwich cell was pulled in the heating stage (Linkam TST350). The temperature range and pulling speeds were 25 °C and 3 μm/s, respectively.
The optical textures of the fabricated DNA film were directly observed by POM (Nikon LV100POL) using a first-order retardation plate (λ = 530 nm). Fluorescent confocal polarising microscopy (C2 plus, Nikon) with a linearly polarised laser source (λ = 488 nm) was used to observe the meniscus line of the DNA microstructures. For this experiment, the DNA solution was mixed with a fluorescent dye molecule, Acridine orange (Aldrich).