Vacuum sputter coater

Cleaned webspinner silks were secured to conductive carbon tape, then were gold coated using a Denton vacuum sputter coater for 3 minutes at a deposition rate of 5 nm min⁻¹. The SEM was performed using a XL30 Environmental SEM-FEG built by FEI. The secondary electron (SE) detector was used for imaging. Images were collected under a vacuum pressure of less than 9 × 10⁻⁵ mbar and with a beam current of 5 kV. SEM images were processed using Gwyddion version 2.31 to measure fiber diameters from multiple images.³⁷

Twelve millimeter coverslips were etched in piranha solution (3:1 mixture of sulfuric acid and 30% hydrogen peroxide) at room temperature for 15 min, cleaned with deionized (DI) water, and then incubated with 0.01% poly-L-lysine overnight. After rinsing in DI water, the coverslips were placed into a 24-well plate. Zymosan particles were added and incubated on the coverslips for 3 h at room temperature to ensure particle adhesion. Samples were sequentially dehydrated by 30, 50, 75, 90, and 95% ethanol on ice for 5 min each time and 100% ethanol for 5 min, 3 times. Samples were dried using a Leica CPD030 Critical Point Dryer and then sputter-coated with a 10 nm thick film of Pd/Rh alloy using a Denton Vacuum Sputter Coater. Coated samples were imaged using an FEI Quanta 600F SEM with 30 kV voltage, high pressure, and 5–6 mm working distance.