2.3. Lap-Shear Bonding Strength

Lap-shear bonding strength was tested according to the method of ASTM F2255-05 [33]. Fresh porcine skin was purchased from a local market (South Burlington, VT, USA). The skin graft was cut into the dimensions of 5.08 cm × 2.54 cm × 0.24 cm with a #20 Uniblade^TM disposable surgical scalpel (AD Surgical, Sunnyvale, CA, USA), The skin strip was glued on an aluminum block with dermal side up by using a Loctite^® super glue (Henkel Corporation, Rocky Hill, CT, USA). The test specimens were kept moist by being wrapped in gauzes soaked with phosphate-buffered saline (PBS) (Fisher Scientific, Fair Lawn, NJ, USA) and placed in an environmental chamber at 23 °C and 50% relative humidity. A total of 100 µL of WPI solution and 25 µL of GTA solution was applied to the skin’s dermal side, mixed with a small steel spatula, and then lapped with another porcine skin strip backed by the fixture as described in Figure 2. The bonding area was 2.54 cm × 1.0 cm. The newly glued specimens were being clamped by Staples^® #4 Bulldog clips (purchased from Staples, South Burlington, VT, USA) and conditioned at 23 °C for 30 min being wrapped by PBS soaked gauzes. The lap-shear bonding strength was tested by an Instron 5566 universal testing machine (Instron Corporation, Canton, MA, USA). The glued specimens were placed in the grips (maximum load: ±500 N) of the Instron testing machine and operated at a rate of 10.00 mm/min until the test specimens ripped apart. The maximum load (N) was recorded and lap-shear bonding strength (kPa) was calculated by dividing the maximum load (N) by the bonding area 1.00 cm × 2.54 cm).

Depiction of lap-shear bonding strength testing apparatus.