Laser-assisted bioprinting at different wavelengths and pulse durations with a metal dynamic release layer: A parametric study

Abstract

For more than a decade, living cells and biomaterials (typically hydrogels) are printed via laser-assisted bioprinting. Often, a thin metal layer is applied as laser-absorbing material called dynamic release layer (DRL). This layer is vaporized by focused laser pulses generating vapor pressure that propels forward a coated biomaterial. Different lasers with laser wavelengths from 193 to 1064 nanometer have been used. As a metal DRL gold, silver, or titanium layers have been used. The applied laser pulse durations were usually in the nanosecond range from 1 to 30 ns. In addition, some studies with femtosecond lasers have been published. However, there are no studies on the effect of all these lasers parameters on bioprinting with a metal DRL, and on comparing different wavelengths and pulse durations -except one study comparing 500 femtosecond pulses with 15 ns pulses. In this paper, the effects of laser wavelength (355, 532, and 1064 nm) and laser pulse duration (in the range of 8 to 200 ns) are investigated. Furthermore, the effects of laser pulse energy, intensity, and focal spot size are studied. The printed droplet volume, hydrogel jet velocity, and cell viability are analyzed. Keywords: bioprinting, laser-assisted bioprinting, laser-induced forward transfer, laser absorption layer, laser parametric study *Correspondence to: Lothar Koch, Laser Zentrum Hannover e.V., Nanotechnology Department, Hollerithallee 8, 30419 Hannover, Germany; Email: l.koch@lzh.de

Laser-induced Forward Transfer Hydrogel Printing: A Defined Route for Highly Controlled Process

“…The main component of the system is a laser source, which determines the main characteristics of the laser pulse. The most common, commercially available, and studied[ 19 , 20 ], laser sources have nanosecond pulse length[ 21 - 24 ] and a wavelength of λ = 1064 nm (near infrared range). Near-IR radiation is well absorbed by the metal absorbing layer, while remaining transparent to living tissues and cells[ 25 , 26 ].…”

“…When choosing a laser source and an radiation optical focusing scheme, the following laser factors should be considered ( Figure 1 ): Pulse duration, laser pulse energy, and laser spot size, since these parameters directly determine the energy density (fluence)[ 16 , 21 , 30 , 31 ], and peak laser power. However, the vapor bubble growth dynamics and all LIFT laser transfer process[ 19 , 21 ] depend on the pulse duration and absorbed fluence, which is, in turn, determined by the laser radiation absorption coefficient of the energy absorbing layer. The choice of material and thickness of the ribbon absorbing layer are associated with the need to provide the most efficient conversion of a laser pulse with a given wavelength λ into heat, while minimizing transmitted radiation, which can adversely affect biological objects contained in the hydrogel layer.…”

3D Bioprinting in Tissue Engineering for Medical Applications: The Classic and the Hybrid

“…Energy absorbed from this step vaporizes a portion of the donor layer to create a high-pressure bubble that propels the bioink onto the receiving substrate in the form of droplets. The quality of LAB-printed constructs is determined by many factors, such as the laser’s wavelength, intensity, and pulse time [ 55 ]; the surface tension, thickness, and viscosity of the bioink layer; the wettability of the substrate; and the air gap between the “ribbon” structure and the substrate [ 56 ].…”

3D Printing of Artificial Blood Vessel: Study on Multi-Parameter Optimization Design for Vascular Molding Effect in Alginate and Gelatin

“…In the past few years, many functional tissues and organs were manufactured by 3D printing systems such as inkjet-based printing [13,14,15], micro-extrusion printing [16], and laser-assisted printing [17,18,19], which have different forming parameters in different 3D printing system. One important challenge is the material viscosity characteristic which can determine the types of 3D printers.…”