5565 universal testing machine

The tensile test was performed based on the ASTM D3574–17 standards with rectangular-shaped specimens. Instron 5565 Universal Testing Machine was used to determine the tensile strength (kPa). The test was performed with a minimum grip separation of 62.5 mm at a grip crosshead separation speed of 500 ± 50 mm/min. Ultimate Elongation was measure using Equation (1).
$\%\mathrm{Ultimate} \mathrm{Elongation}=\frac{\left[{\mathrm{d}}_{\mathrm{f}}-{\mathrm{d}}_{\mathrm{o}}\right]}{{\mathrm{d}}_{\mathrm{o}}}$
where:
d_o = original distance between grips (which was set to 62.5 mm in all the tests)
d_f = distance between the grips at rupture/breakpoint.

The tear test was performed on the Instron Universal 5565 testing Machine (shown in Figure 8) following the ASTM D3574 standard test method. Figure 8B shows the specimen for the tear test with a rectangular-shaped slit. The specimen is clamped in the jaws of the Instron 5565 Universal testing machine, ensuring that the jaws grip the specimen uniformly and properly, as shown in Figure 8A. The crosshead speed of grip separation was 500 ± 50 mm/min. Tear strength was calculated using maximum force registered on the Instron 5565 Universal testing machine and the average thickness of the specimen as given by Equation (2).
$\mathrm{Tear} \mathrm{strength} \left(\frac{\mathrm{N}}{\mathrm{m}}\right)=\frac{\mathrm{F}}{\mathrm{T}}\times {10}^3$
where:
F = force, N, and
T = thickness, mm
At least three replicates per formulation were tested, and the average values were reported in N/m.

Compressive force-deflection (CFD) measures the force needed to produce a 50% compression over the foam specimen’s entire upper area. For this test, the Instron 5565 Universal testing machine (shown in Figure 9) was used, and ASTM D 3574 -17 test method was followed. The samples were compressed twice, first to a deflection of 75% and then to 80% of the original thickness. The specimen was compressed at a rate of 50 ± 5 mm/min to 50% of its original thickness, and the final force was recorded, in N, after 60 ± 3 s, while keeping the specimen compressed. The compression stress at a 5–6% compression strain was used to calculate the compression modulus of the samples.

Rats were sacrificed at 21 days post‐injury. Both wounded and unwounded hind Achilles tendons together with calcaneus and 1 cm proximal muscle were harvested and tested within 2 h from the harvest time point. Adherent surrounding tissues and other muscles were removed completely. Ultimate tensile strength was tested using an Instron 5565 Universal Testing Machine (Instron, High Wycombe, UK). The tendon specimen was fixed by two clamps of Instron. One clamp was placed at the musculotendon junction and the other was placed at the attachment of Achilles tendon to the calcaneus. The distance between the clamps is 10 mm. Pneumatic grips and silicon carbide waterproof papers were used as padding to avoid specimen slippage. $$\text{Strength recovery ratio}=S_{\mathrm{p}}/S_0\times 100\%$$
Here, the S_p and S₀ represent the breaking strength at 21st days postoperation and preoperation, respectively.
A linear portion of the elastic phase of the curve was marked and tendon stiffness (N/mm) was calculated from the slope of the force‐displacement curve.¹³⁸, ¹³⁹ $$\text{Stiffness recovery ratio}=F/D\times 100\%$$
Here, F represents the force applied to the Achilles tendon in the tendon's elastic phase and D represents the displacement the tendon experiences when the force is applied.

An Instron 5565 Universal Testing Machine was used to carry out tensile strength tests. The Instron is calibrated periodically using a set of reference weights that are certified annually by the National Metrology Lab, Dublin. In terms of standardizing the tensile strength tests performed using this type of instrument, there is no material with a known stress strain graph that can be used repeatedly without suffering fatigue itself. Such a material would make the calibration temperature sensitive, as it would be likely to exhibit different stress strain characteristics at different ambient temperatures. Therefore, the only standards measured for the Instron are force, displacement and time. This factor was taken into consideration when collecting the tensile strength data.
The thin films were cut using a rotary cutter into strips 40 mm to 10 mm in dimension. The samples were clamped in between PDMS supports and provided a gauge length of 20 mm. The strips were pulled apart along the 20 mm edge until they broke cleanly in the middle [32 ]. Test conditions at room temperature included a load of 5 kN, clamp speed of 0.5 mm.min⁻¹ and data acquisition rate of 10 Hz.
For the evaluation of possible anisotropy in the mechanical strength of the films in relation to the direction of travel of the film, strips were cut both parallel and at perpendicular right angles to this direction.

Blocks of PEG hydrogels were tested in compression on an Instron 5565 Universal Testing Machine using a protocol similar to the ASTM D695 standards (Compression of Rigid Plastics). Briefly, the PEG hydrogels were fabricated into a cylinder with diameter of 16 mm and height of 1–2 mm. The Universal Testing Machine was set to compress the material at a rate of 50 mm/min. Triplicate blocks of materials were tested in a hydrated state.
Due to the small size of the suprachoroidal spacer implant candidates (PEG hydrogels made with 0.3, 0.5, and 1.0 mm diameter), it was not possible to directly test the mechanical properties of the implant. Thus, the bend strength of the implant candidates was determined instead. The implants were held 5, 10, 20, and 30 mm away from the bottom tip, and the tip was applied perpendicularly to a balance scale. The maximum force of the implant was recorded for 5 different segments. The same procedure was performed with the PEG hydrogels in their hydrated and dehydrated forms. In some cases, the PEG hydrogel was dip coated in Viscoat (Alcon, Fort Worth, TX) for 5 min and then dried.

SEM images were obtained using a Hitachi SU8220 device. The SEM elemental mapping analysis was conducted using an EDX (Oxford EDS, with INCA software). TEM images were obtained using a JEOL JEM-2100F microscope with an acceleration voltage of 200 kV. Elemental mapping in TEM was conducted using the Bruker EDS System. The XRD analysis was carried out using a Bruker D8 Advance with filtered Cu-Kα radiation (40 kV and 40 mA, λ = 0.154 nm); the step scan was 0.02°, the 2θ range was 2–10° or 2–70°, and the step time was 2 s. FTIR was conducted by Bruker VERTEX 33 units in the wavenumber range of 400–4000 cm⁻¹. The XPS analysis was performed using an ESCALAB 250 spectrometer (Thermo Fisher Scientific) with monochromated Al-Kα radiation (1486.6 eV) under a pressure of 2 × 10⁻⁹ Torr. The AFM images were obtained using a Bruker Multi Mode 8 scanning probe microscope (SPM, VEECO) in tapping mode. The TG measurement was analyzed on a Netzsch STA 449F3 instrument under the flow of N₂. The adsorption isotherms of H₂, CO₂, N₂, and CH₄ on the MXene membranes were measured using a Micromeritics (ASAP 2460) instrument. The mechanical tests were performed using an Instron-5565 universal testing machine (USA).