Model 4465

The surface morphology of the porous HDPE, HDPE/PEAA, and HDPE/PEAA/Col scaffolds was observed under a field emission scanning electron microscope (FE-SEM S4300; Hitachi, Japan) after sputter-coating with platinum. The chemical bonds and elemental composition were characterized by Fourier transform infrared (FT-IR; Mattson, Galaxy 7020A) spectroscopy and electron spectroscopy for chemical analysis (ESCA; ESCA LAB VIG microtech, Mt 500/1, and so forth, East Grinstead, UK), respectively.
Tensile properties were measured via a universal testing machine (Instron, model 4465) with a Zwick Roell tensile tester equipped with a 1 kgf load cell, at 25 °C with an extension speed of 10 mm/min. The tensile strength and Young’s modulus measure of each sample were calculated from the averages of 10 specimens.
The porosity of the porous scaffolds was determined by using a mercury intrusion porosimeter (AutoPore IV 9520; Micromeritics Co., USA). The advancing and retreating contact angles of mercury were taken to be 140° and the surface tension was taken as 0.480 N/m (480 dynes/cm).

The procedure followed in [24 (link)] was adopted to perform the cavity test. However, few changes were made to the system that was used: pressure sensor (Model PRESS-S-000, PENDOTECH, USA) and pressure reader (Model PMAT-S, PENDOTECH, USA) were used to observe the pressure due to the pressurized incompressible fluid (water). In addition, an Instron machine (Model 4465; Canton, MA, USA) was used to introduce the water into the needle-balloon tool. A new design needle-balloon tool was used in this study, the balloon is silicon based with smaller dimensions and has softer mechanical behavior than the one used in the previous study. To ensure no air was entrapped inside the system, its elements (syringe, needle-balloon tool and Y-shaped tubes) were filled with water and submerged under water until they sank and assembled together. Afterwards, the tubes were connected to the pressure sensor with a water inlet and outlet, which allows depleting any remaining air in the system. Nine hydrogel samples were investigated by this test at three different deformation rates: 5 μl/s, 20 μl/s and 50 μl/s. A schematic diagram for the system is shown in Fig 2. In addition, the balloon response was evaluated separately using the Instron machine.

The cooking loss and Warner-Bratzler shear force (WBSF) were measured on a same 3.0-cm thick steak (approximately 200 g) of each muscle sample, as described in our previous work [7 (link)]. Briefly, the samples were placed in plastic bags, sealed with double clips and put in a pre-heated 72°C water bath, and kept until their core temperature had reached 70°C. The core temperature of samples was monitored using a copper-constantan thermocouple attached to a Thermo recorder (Model TR-71U; T & D Corp., Tokyo, Japan). The cooked samples were then immediately cooled for 30 min in a circulatory water bath. After removing the plastic bags and absorbed with wiping papers to remove the surface water, the samples were re-weighed to determine the cooking loss.
After determining the cooking loss, these samples were used for the WBSF analysis. Particularly, 5 representative cores with an average diameter of 0.5 inches and length of about 2 cm were removed parallel to the muscle fiber direction of each sample using a 0.5-inch metal corer. The WBSF values were obtained by completely cutting the cores in an Instron Universal Testing Machine (Model 4465, Instron Corp, High Wycombe, UK) using a crosshead speed of 200 mm/min and a 40 N load cell.