Because the ripples are all oriented perpendicular to the scratching direction, the sides of the Selinexor concentration obtained diamond dots are parallel to and with an angle of 135° to the horizontal line (highlighted by the white area

in Figure 4b). Finally, we used scratching angles of 0° and 45° (as shown in Figure 1e) to scratch the PC surface. Using a feed of 40 nm and normal load of 15.8 μN for a scratching of angle 0° and load of 14.8 μN for a scratching angle of 45°, we formed ripples with a period of 450 nm. The morphology and a FFT image of the fabricated surface are presented in Figure 4c. The length and shape of the dots are the same as the diamond-shaped nanodots above, except that the orientation of the dots has changed, with the sides perpendicular to and with an angle of 135° to the horizontal line (indicated by the white area in Figure 4c). Figure 4 Morphologies and 2D FFT images of 3D nanodot arrays. The scratching angles (a) 90° and 0°, Dactolisib supplier (b) 90° and 45°, (c) and 0° and 45° of the two-step scratching method. The above experimental results reveal that the length and orientation of nanodots can be regulated by manipulating the period of the ripples for a selected scratching direction. Using our two-step scratching method, by changing the period of the ripples formed using different scratching angles, complex, controllable 3D nanodot arrays can be fabricated easily.

Mechanism of ripples formation Anidulafungin (LY303366) As shown in Figure 5a,b, the process of ripple formation on PC sample surface can be presumed as an interaction of stick-slip [11] and crack formation [12] processes. When the tip scratches along the fast scanning direction,

the AFM tip indents the polymer surface and starts to push the surface material. In practice, the tip still sticks to the surface and is forced to hop over until the polymers that builds up in front of the tip offers enough resistance, so the bump is formed. Because the movement of the tip is a zigzag trace, the formed bump will be pushed forward and backward, and the rippling structures perpendicular to the scratching direction can be fabricated. For the typical ripple structures, the AFM morphology and modulus images are shown in Figure 5c,d. It can be found that the tip trace is clearly at the CHIR98014 supplier grooves but blurry at the ridges, which also confirmed that such ripples structures could be a stick-slip phenomenon. The cross-sections of the height and Young’s modulus of the ripples are shown in Figure 5e. The moduli are about 1.5 and 2.5 GPa at the ridges and grooves, respectively. For the raw PC surface, the modulus is about 2.45 GPa. The changing of the modulus may be a consequence of the crack existing within the bumps, which agrees well with the model that proposed by Dr. Khrushudov [12], as shown in Figure 5a. For the 3D nanodots arrays, the AFM morphology and modulus images are shown in Figure 5f,g.