*2.2. Preparation of Micron-Size White Bamboo Fibrils*

The MWBF was fabricated from raw white bamboo using both a steam explosion following alkaline treatment technique and the mechanical extraction method (microgrinding). Raw white bamboo (~3 years old) was first cut into bamboo culms of 50–60 cm in length using a saw machine, and placed into an autoclave with over-heated steam at 175 ◦C and 0.7–0.8 MPa for 60 min. The steam was then released suddenly for 5 min and the cycles of sudden steam release were repeated 9 times. Subsequently, samples were immersed in a 2% NaOH solution at 70 ◦C for 5 h to ensure the complete removal of the cell walls. The roller looser was then used to extract the slabs into small fibers. Finally, they were washed with fresh water until they were neutralized, and dried in an oven for 24 h at 105 ◦C. The resulting fibers were dispersed in water with a fiber content of 10 wt.%. They were then cut into pulp fibers using a food mixer. The pulp fibers were passed 15 times between static grind and rotating grind stones revolving at 1500 rpm (MKCA6-3, Masuko Sangyo Co. Ltd., Saitama, Japan). The obtained MWBF (water slurry with 90% water) was treated with ethanol to remove the water and filtered using a vacuum pump to obtain a sheet of MWBF. The filtered sheet of MWBF was stirred with an additional amount of ethanol using a stirrer at 5000 rpm for 15 min. The morphology of the MWBF was examined by scanning electron microscopy (SEM) (JEOL, Tokyo, Japan), as shown in Figure 1. The SEM in Figure 1 indicates that the diameter of cellulose fiber is in range from 90 nm to 0.2 μm, but its length is in the order of tens of micron.

**Figure 1.** Picture of white bamboo (**A**), micron-size white bamboo fibrils (MWBFs) (**B**), and SEM image of MWBFs (**C**).
