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Lou, et al.
A B

C D

Figure 2. (A) Schematic diagram of experimental equipment. (B) The process of composite coating. (C-D) Model of introducing GO into
the coating.
(4 mm/s) in the horizontal direction relative to the fixed Table 2. Each sample corresponds to the additive phase in the
substrate along the designed path provided by the model plating bath.
file (Figure 2B). As the number of reciprocating scans Sample WNC PNC GNC
increases, the thickness of the coating increases layer by Nickel particles (g/L) 0 2 2
layer, and finally a three-dimensional geometric model is Graphene oxide (g/L) 0 0 0.5
formed. The size of the scanning area is 20 × 20 mm .
2
The jet from the nozzle hit the surface of the cathode and
spread around, and the diffused plating bath was collected WNC and the coating prepared with Watts nickel bath
by the external container and reused. In the initial stage added with Nip was named PNC. The list of samples is
of deposition, the nickel ions were reduced at the cathode shown in Table 2. The deposition time for each sample is
to form a pre-deposited nickel coating. At the same time, 30 min. In addition, a pure titanium sample (TI) was set
a large number of Nip also impact the surface of the to evaluate the influence of the substrate. The magnetic
cathode along with the jet. Under the action of an external field only used to promote the doping of Nip carrying
magnetic field, the pre-deposited nickel coating and the GO during the preparation process of the coating. In
ferromagnetic Nip were simultaneously magnetized to the absence of a magnetic field, Nip and GO cannot be
generate opposite magnetic poles. The Nip are attracted effectively deposited on the cathode surface (Figure S4).
to the surface of the cathode nickel coating along the In the subsequent antibacterial test, there was no difference
magnetic line of induction [41,43] . A part of the Nip will be between the failed coating and the pure nickel coating
transferred out of the cathode surface under the impact of prepared by Watts nickel bath. Thus, the coatings prepared
the jet, and the remaining part of the Nip can come into without a magnetic field have not been discussed.
contact with the nickel coating. The exposed area of the
Nip surface (not covered by GO) can be used as a site 2.4. Surface characterization
for combine with the nickel coating (Figure 2C). The
Nip combined with the coating to form strong adsorption. Surface morphologies of the coating on the samples
At high current density, a large amount of nickel ions are were observed using a field emission scanning electron
deposited on the surface of the cathode. The growing microscope (Hitachi Instruments, S-4800, Japan)
coating wraps and fixes these particles in the coating to equipped with an energy dispersive spectrometer (EDS)
obtain a GNC (Figure 2D). to examine the chemical composition. Raman microscopy
To evaluate the influence of nickel plating and was used to observe the Raman spectra of the GO powder
Nip on the antibacterial activity of samples, the coating and GNC using a laser wavelength of 532 nm (Thermo
prepared with traditional Watts nickel bath was named Fisher Scientific, DXR 2X, USA).

International Journal of Bioprinting (2022)–Volume 8, Issue 1 99