Figure 3: Distance (s) of droplets as a function of measured time (t) on coated paper, office paper, wove paper, respectively.
The inset shows the sketch map of force analysis of the droplet in the gliding process.
Figure 4: Surface morphologies of three typical papers.
AFM images (2 × 2 μm2) of surfaces of Wove paper (A), Office paper (B) and Coated paper (C), respectively.
Coated paper with high smoothness and brightness is an advanced paper substrate which has been commonly used in printing book cover, elegant advertisements, commodity packaging, and labels, etc. It is mainly manufactured by coating a pigment compounds layer on base-paper.
nd Kaolin (mainly Al2O3·2SiO2·H2O), as well as chemical additives such as dispersants, resins, sodium polyacrylate (NaPA), and poly (styrenebutadiene) (SB) latex binder etc. Investigations have been conducted to confirm that addition of the the above-mentioned fillers has a positive effect on the adhesion of paper, . In order to further disclose the mechanism for the surface adhesive, an energy dispersive spectroscopy (EDS) analysis was also conducted to survey the surface elements of the tested coated paper.
5 exhibits the weight ratio of various elements on the surface of the coated paper. It can be seen that oxygen and silicon elements occupy a large proportion among all elements. As a result, combined with the former efforts, a better compatibility between paper and ink can be obtained through properly oxidizing GaIn24.5 alloy ink.
Figure 5: Energy dispersive spectroscopy (EDS) picture of elements on coated paper surface.
Automatic printing of circuits on coated paper
Automatic printing of GaIn24.5 based inks on coated paper was implemented utilizing the developed system, and the direct printing process was illustrated in Fig. 6. Through the evaluation as performed above, here the commercially available coated paper (with a weight specification of 200 g/m2) was adopted as the printing substrate. Apparatus equipped with single printing syringe A or B were utilized and the structure materials of matched printing needle were porous brush and orifice metal, respectively. In addition, syringe A and B were respectively loaded with GaIn24.5 ink and RTV silicone rubber. During the printing process, syringe A was firstly installed to print required patterns on coated paper according to the digitalized program, and then overprinted by RTV silicone rubber from syringe B. When necessary, multilayer circuit structures can be fabricated by sequentially printing liquid metal circuitries bypassing the upper surface of the cured silicone rubber. In this way, a three dimensional (3D) hybrid electro-mechanical device on paper can be quickly printed out.
