L. Koch
O. Brandt
S. Ganske
A. Deiwick
B. N. Chichkov

Investigation on the influence of laser wavelength and pulse duration on the laser-induced forward transfer of cells

International Conference on Biofabrication
7.-9. November
Utrecht
2015
Type: Konferenzbeitrag
Abstract
Different groups use the laser-induced forward transfer for printing biomaterials including living cells. Therefore, they apply lasers with different wavelength (193 – 355 nm and 1064 nm) and different pulse durations (1 – 30 ns and 500 fs) and different laser absorption materials (metals, polymers, bi-layered systems or the biomaterial to be printed). Dinca et al. [1] compared printing of alginate and cell medium with 500 fs and 15 ns pulse duration at 248 nm wavelength. However, so far there is no systematic investigation of the influence of these laser parameters on the printing of biomaterials and cells. We applied lasers with different parameters, like wavelength (355, 532, 1064 and 2940 nm), pulse durations (1 ns – 1 µs), and pulse energy for laser-induced forward transfer with different absorption materials to investigate the influence of these parameters on printed hydrogel droplets and cell viability. Methods: The principle setup for the laser-induced forward transfer consists of two coplanar glass slides. The upper slide is coated underneath with a laser absorbing layer and a layer of the biomaterial (usually cells embedded in a hydrogel) to be transferred. Laser pulses are focused through the upper glass slide into the absorbing layer. By evaporating this layer in the laser focus, a vapor bubble is generated that expands and propels the biomaterial underneath towards the lower glass slide [2]. After a few micro-seconds, the bubble re-collapses. Due to inertia and surface tension, the gel forms a jet, flowing to the lower glass slide, where it deposits as a droplet. Results + Conclusion: The laser-induced forward transfer of hydrogels and the printing of vital cells can be initiated with laser pulses with wavelength from ultraviolet to mid-infrared and a wide range of pulse durations from femto-seconds to micro-seconds. However, the successive temporal parts of the laser pulse have varying impact on the printed droplet volume. Additionally, there are differences in the jet formation process, achievable droplet size, and applicable laser absorption material.