Biomedical Engineering Reference
In-Depth Information
y
= 1.54 x R
2
= 0.993
Sprayed collagen (mg)
FIGURE 6.22
Relationship between thickness of collagen coated onto a stent and amount of collagen sprayed by an air
brush.
was added into the aqueous collagen to visualize the uniformity of the coating. To prevent
dissolution of the collagen coating, aqueous genipin (0.4 mL, 5% by w/v) solution (con-
taining 70% ethanol by v/v) was directly spray-coated onto the collagen-coated stent. The
cross-linking process occurs in a sealed tube at 37°C for 1 day. By repeating this procedure
three times followed by air drying for 24 h, the thickness of collagen layer was found to
be proportional to the quantity of collagen sprayed (Figure 6.22), an 8-
μ
m collagen coating
was prepared using approximately 5 mg collagen in a spray coating process (Figure 6.23).
Ink-Jet Technology
The fundamental principles of reagent jetting are described and summarized below
(Tarcha et al., 2007). During the jetting process, a capillary chamber is filled with reagent
solution. By applying voltages to the wall of the capillary, a distortion is caused, resulting
in capillary expansion and pressure drop, and the drawing-in of more reagents into the
capillary. When the voltage is released and the capillary returns to its original volume, a
droplet is expelled through the print nozzle orifice (Figure 6.24). Ink-jet printing technol-
ogy can dispense spheres of fluid with diameter of 15-200
μ
m (2 pL to 5 nL) at rates of
1 MHz for continuous droplets (continuous mode jetting) and 1 Hz to 25 kHz for single
Air brush
Rotating stent
FIGURE 6.23
Schematic illustration of spray-coating equipment used in the study.
