Computational fluid dynamics of impinging microjet for a needle-free skin scar treatment system

Current engineering and clinical aspects of needle-free injectors: A review

“…Air or gas powered Stagnation pressure [15][16][17] No significant variation for nozzle diameter range of 129-259 µm [15,16]. Peak stagnation pressure increased with nozzle diameter (nozzle range: 100-200 µm) [17].…”

“…The force required for driving the piston could be generated by an expanding gas (usually CO 2 or N 2 ) or air [15][16][17][18], the energy from the sudden release of a compressed spring [19][20][21], the Lorentz actuators [22][23][24] or piezoelectric actuators [25][26][27]. The Lorentz and piezoelectric actuators could provide electronic control over the injection speed.…”

“…Expanding gas or air is commonly used as the operating force in many commercially available NFJIs [4,15,17] possibly because compressed gas can provide a higher energy density, improved flexibility and could deliver larger volumes of drugs. In these devices, an expanding gas accelerates the firing piston or ram, which in turn energizes the fluid to be injected by creating a high-pressure pulse.…”

“…One of the main factors limiting the applicability of current systems is jet diffusivity, which leads to the formation of a large dispersion pattern and unreliable penetration [29]. The diffusive jets may have increase in their jet diameter with the increase in stand-off distance and may affect the stagnation pressure on the skin surface [17,24,37]. The diffusive nature of the jets may be a reason to the pain and bruising associated with the current systems [26,29].…”

“…Several studies have shown that a vaccine delivered using Stagnation pressure [15][16][17] and penetration depth (gelatin [18], cadaver [44])…”