5967 universal testing machine

The visual aspect of the nanopapers was assessed with a commercial camera; micrographs were recorded with an Eclipse E600 (Nikon, Tokyo, Japan) microscope working in reflection. CIEL*a*b* color properties were recorded with a PCE-CMS 7 ( PCE Instruments Albacete, Spain). The average values were used to obtain the differences between each color value (ΔL*, Δa* and Δb*), which corresponded to lightness, redness/greenness and yellowness/blueness.
Mechanical properties of the elaborated nanopapers were analyzed in terms of their tensile resistance. Tests were performed using a 5967 Universal Testing Machine (Instron, Norwood, MA, USA) equipment provided with pneumatic clamps and with a 250 N loading cell and a speed of 5 mm min⁻¹. Samples were prepared, dog bone-shaped, 38 mm long, with a width of 5 mm and 0.065 mm thickness. The starting distance between the clamps was 20 mm.
Two barrier properties of the nanopapers were evaluated: UV resistance and surface wettability. The UV–vis light transmittance spectra were measured in a 200–900 nm wavelength range using a V-730 spectrophotometer (Jasco, Tokyo, Japan).The contact angle of the sessile drop was measured with an OCA20 contact angle system (Data Physics, San Jose, CA, USA). The Owens, Wendt, Rabel and Kaelble (OWRK) [45 (link),46 ,47 (link)] method was used to determine the surface free energy with polar and dispersive components.

The mechanical properties of the tissue before and after decellularization were measured by indentation testing. As previously described (Omidi et al., 2014 (link); Li et al., 2022 (link)), the specimens of adipose tissue, dermal tissue, DAM, and ADM were cut into disks with a 6-mm diameter (n = 5) using a corneal trephine and tested using a 5967 Universal Testing Machine with a 100-N load cell (Instron, Norwood, MA). For unconfined compressive testing, the specimens were compressed at 10 mm/min via the indenters until 100N strain was reached. The yield point was determined, and the yield strength (kPa) was recorded. Young’s modulus was calculated by the slope of linear compression phase of the stress-strain curve.

Flat specimens, with a thickness of 1 mm, were employed for uniaxial tensile testing; these were sectioned from the recrystallized samples near the surface along the TD direction using electrical discharge machining (EDM). An oxidation layer that occurred during EDM cutting was subsequently removed carefully using mechanical grinding. The gauge length and width of the tensile specimens were 10.2 and 3.2 mm, respectively. Uniaxial tensile tests were carried out at room temperature on an Instron 5967 universal testing machine (Instron, Norwood, USA) at the strain rate of 1 × 10⁻³ s⁻¹. The strain evolution during the tensile tests was monitored by the displacement transducer on the testing machine, but was accurately measured during testing using an Advanced Video Extensometer camera and digital image correlation techniques. At least three samples for each material were tested to confirm reproducibility.