## 2 Materials and Methods
### Testing and Characterization  
The chromatic aberration of the surface coating was measured with HP-2136 chromatograph (Shenzhen Threenh Technology Co., Ltd., Shenzhen, China). \(L\) indicates brightness, \(a\) indicates a red-green hue, and \(b\) indicates a yellow-blue hue. A set of data including \(L_{1}\), \(a_{1}\), and \(b_{1}\), were output with the chromatograph at one point on the coating. Another set of data, \(L_{2}\), \(a_{2}\), and \(b_{2}\), were measured with the chromatograph at the other point on the coating. According to the formula (1), \(\Delta L=L_{1}-L_{2}\) (difference in brightness), \(\Delta a=a_{1}-a_{2}\) (red/green difference), \(\Delta b=b_{1}-b_{2}\) (yellow/blue difference), chromatic aberration value \(\Delta\)E was calculated:  
\[\Delta\mathrm{E}=\left[(\Delta L)^{2}+(\Delta a)^{2}+(\Delta b)^{2}\right]^{1 /2} \tag{1}\]  
The gloss of the coating was measured with HG 268 Smart Gloss Meter (Shenzhen Threenh Technology Co., Ltd., Shenzhen, China) by the standard GB/T 4893.6-2013 (Shenzhen Threenh Technology Co., Ltd., Shenzhen, China). The gloss of the coating at 20\({}^{\circ}\), 60\({}^{\circ}\) and 85\({}^{\circ}\) of incidence was recorded, respectively. According to ISO 15184.1998 \"Paints and varnishes--Determination of coating hardness by the pencil method\" (Shenzhen Threenh Technology Co., Ltd., Shenzhen, China) was used to apply force evenly perpendicular to the coating surface, and then the cutting lines were formed on the coating. The above operations were repeated on the coating surface to form a 90\({}^{\circ}\) intersection with the original cutting lines to achieve a grid pattern. Then the grid was covered completely with adhesive tape, and the adhesive tape was held for a period of smooth tearing within 5 min. The coating adhesion grade was determined according to the coating breakage on the tape. There were grades of 1-5 in total, and grade 5 was the worst (Shenzhen Threenh Technology Co., Ltd., Shenzhen, China). The coated wood plate was placed on the impact tester to ensure that the steel ball in the center of the impact part could be lifted for a certain height to make the steel ball strike the wood board by free-falling method. Whether the coating was damaged was observed. The maximum height which made coating damage was recorded as the impact strength (Shenzhen Threenh Technology Co., Ltd., Shenzhen, China) (Shenzhen Threenh Technology Co. The 15% sodium chloride solution (self-made), 70% ethanol solution (Qingdao Heino innover Disinfection Technology Co., Ltd., Qingdao, China), detergent which contained fatty alcohol ethylene oxide of mass fraction of 25% and water of mass fraction of 75% (Shanghai White Cat Co., Ltd., Shanghai, China) and red ink (Shanghai Fine Cultural Products Co., Ltd., Shanghai, China) were used to test the liquid resistance of the waterborne coating [41]. The surface of the coating was wiped clean. Then, the filter paper soaked with the solution was tiled on the four areas on the coating surface. After being placed in the sealed tank and standing for 48 h, the filter paper was withdrawn. Then the residual reagent on the coating was sucked dry with paper and standing for 16 h. The surface damage and impression of the test area were observed, and then the color difference and gloss were measured. The appearance of microcapsules was observed by the Quanta-200 scanning electron microscope (FEI Co., Ltd., Hillsboro, OR, USA). The chemical composition of microcapsules and coatings were gauged by VERTEX 80 V infrared spectrum analyzer (Germany Bruker Co., Ltd., Karlsruhe, Germany). The specific test parameters included the test range of 4000-500 cm\({}^{-1}\), the time of scanning test of 16 s and the resolution of 4 cm\({}^{-1}\). The microcapsule powder and KBr were mixed and crushed for tablet pressing. The sample was placed on the test bench, and the infrared spectrum was obtained through the computer analysis connected with the equipment.