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Xie, et al.
and retain the antibacterial activity of the Cu-containing JSM-5600LV, JEOL Co., Tokyo, Japan) equipped with
Mg alloy. This method can produce antibacterial Mg- energy dispersive spectroscopy (EDS, JSM-5910LV,
based alloys with the desired lower corrosion rate. JOEL Ltd., Japan). Intermetallic second phases were
Furthermore, mechanical properties may be improved by analyzed using X-ray diffraction (XRD) monochromatic
alloying and grain refinement. Previous work indicated Cu-Kα radiation at 15 mA and 30 kV, with scattering
that ZK30 (Mg-3Zn-0.5Zr) had good mechanical angles ranging from 10° to 80°, step size 0.02° and
properties and biodegradation resistance [13,23] . When Cu scanning speed 8°/min. The hardness was measured using
was added to ZK30 by SLM, SLMed ZK30-0.2Cu had a microhardness tester for 10 s under 2.942 N load.
a uniform microstructure, good cytocompatibility, and
antibacterial performance . 2.3. Electrochemical tests
[23]
In this study, SLM was used to produce antibacterial
Mg alloys from Cu powder (0.2 wt.% Cu), Mn powder The electrochemical behavior of SLMed ZK30-0.2Cu-
xMn alloys at room temperature in simulated body
(0, 0.4, 0.8, 1.2, and 1.6 wt.% Mn), and ZK30 powder. The fluid (SBF) was characterized by potentiodynamic
microstructure, hardness, biodegradation, antibacterial
performance, and cytotoxicity of these alloys were polarization curves, measured using an electrochemical
investigated. This proposed method is a new approach for workstation (MULTI AUTOLAB M204). The ionic
the composition design and the manufacturing process concentrations of the standardized SBF solution that
to develop novel antibacterial Mg-based biodegradable corresponds to the concentration of the ions in the blood
alloys. are shown in Table 2. The specimen with the exposed
area of 0.8 mm × 0.8 mm was encapsulated with epoxy
2. Materials and methods resin and a Cu wire was used as the conducting wire. The
polarization curve was measured by a three-electrode
2.1. Materials preparation configuration. The specimen was the working electrode
Gas atomized spherical ZK30 powder, pure Cu powder (WE), a platinum gauze (25 mm × 25 mm; 60 mesh) was
(99.9%), and irregularly shaped pure Mn powder (99.9%) the counter electrode (CE). A saturated Ag/AgCl electrode
were used. The composition of ZK30 powder is presented (in saturated KCl) was the reference electrode (RE).
in Table 1. The ZK30 powder was mechanically mixed Potentiodynamic polarization curves were measured at a
with 0.2 wt% Cu powder and different content of Mn scan rate of 5 mV/s after the specimen was immersed for
powder (0, 0.4, 0.8, 1.2, and 1.6 wt%) was added by ball 2500 s at the open circuit potential and steady corrosion
milling at a rotation rate of 150 rpm in the atmosphere conditions had been established. The biodegradation rate
[14]
−1
of SF (1 vol%) and CO (balance) for 180 min. ZK30- (P , mm year ) was calculated from the corrosion current
i
2
6
0.2Cu-xMn alloys (x = 0, 0.4, 0.8, 1.2, and 1.6) were density (i , mA cm ), using [25,26] :
−2
corr
produced using a self-regulating SLM system in a P = 22.85 i (i)
[24]
chamber filled with high purity argon. The fiber laser i corr
had an output power of 500 W and a wavelength of
1064 nm. The minimum focused spot diameter of laser 2.4. Immersion tests
beam was 50 μm. The parameters of the process are as Immersion tests were conducted on the basis of ASTM
follows: The spot size was 150 μm, scanning speed was G31-72 (the ratio of the solution volume [mL] to
at 200 mm/min, laser power was 80 W, and the specimen specimen surface area [cm ] was 30:1) in SBF solution
2
size is 8 mm × 8 mm × 5 mm. for 168 h. The initial weight of specimen was recorded
2.2. Microstructural and mechanical before immersion, the degradation solution was refreshed
every 24 h to keep the pH value at about 7.4. Funnels
characterizations were used to collect the evolved hydrogen by covering
The specimens of the SLMed ZK30-0.2Cu-xMn alloys the samples. The specimen was cleaned using acetone and
were metallurgically ground and polished and etched in water to remove the corrosion products and then weighed.
−1
a solution of nitric acid and alcohol (4 mL nitric acid and The biodegradation rate (P , mm y ) was calculated
h
96 mL ethanol) for 5 – 10 s. The microstructures were from hydrogen evolution rate (V , ml/cm day) and the
2
h
characterized using optical microscopy (OM, Leica biodegradation rate (P , mm year ) was calculated from
−1
w
DMI 3000 L) and scanning electron microscopy (SEM, the weight loss rate (ΔW, mg cm d ) using [25,26] :
−2
−1
Table 1. The composition of the ZK30 powder (wt%)
Powder Mg Zn Zr Al Cu Fe Mn Ni Si
ZK30 96.34 3.16 0.48 0.002 0.002 0.01 0.0068 0.0036 0.01
International Journal of Bioprinting (2021)–Volume 7, Issue 1 79