Ultra-Short Pulse Laser Ablation of Biological Hard Tissue and Biocompatibles

Abstract

Direct-writing techniques are adequate tools for rapid prototyping of diverse materials, since they avoid the usage of moulds or masks. Among them, laser-induced forward transfer (LIFT) has become a promising tool for rapid prototyping of microdevices due to the high focusing power of lasers, which provides a high resolution, and also to their non-contact and orifice-free nature, which avoids clogging and thus allows working with a wide range of materials. This makes LIFT an appropriate tool for biosensors preparation. In this article, immunoglobulin (IgG) microarrays were prepared through LIFT varying the laser pulse energy. It was found that there exists a minimum energy threshold, E min , below which no material is deposited. Moreover, an analysis of the droplets volumes revealed a linear dependence of this parameter with the laser pulse energy, what allowed finding the existence of an energy density threshold, which is considered to be the threshold to generate an impulsion on the liquid film that only results in droplet ejection when the total energy overcomes E min . Finally, the bioactivity of the transferred proteins was tested, showing no loss of their activity along the whole laser pulse energy range.

Laser Technology for Caries Removal

“…These lasers, commonly called as USPL (ultra short pulse lasers), operates at very high repetition rate (larger than 15 kHz) and energy per pulse typically of hundreds of µJ (Wieger et al, 2006). Although USPLs have extremely higher repetition rate (> KHz) and peak power (up to TW), previous studies relate that a single ultra short laser pulse removes significantly less volume of dental tissue when compared to conventional Er:YAG laser removal (Strassl et al, 2008). This fact occurs due to the differences in focal size and penetration depth of USPLs (which are severely lower when compared to Er:YAG lasers that operate at pulse width of µs); in this way, the pulse repetition rate had to be increased in USPLs to obtain a similar ablation volume than those obtained by Er:YAG (Wieger et al, 2006).…”

“…Another strategy for cooling the tissue during laser irradiation is reducing the pulse duration (Seka et al, 1995). Depending on the pulse duration (<1 ps), the process of ablation is changed and the non-linear processes (or non-thermal ones) take place (Ana et al, 2006;Freitas et al, 2010;Kruger et al, 2008;McDonald et al, 2001;Niemz, 2004;Strassl et al, 2008).…”

“…The USPLs were first developed to allow spectroscopic and electrical conductivity measurements (Strickland & Mourou, 1985) and, according to Strassl et al (2008), studies concerning the use of USPLs for medical applications started more than 15 years ago. In fact, one of the first studies that report the use of lasers with pulse widths of ps and fs was performed by Stern et al (1989), relating applications for corneal ablation.…”

“…Due to the extremely short pulse length, these systems promote precise cutting and have a strong potential for obtaining well-defined cavities and controlled caries removal (Niemz, 2004;Serbin et al, 2002). Also, due to the use of low energies per pulse, it is possible to adjust parameters bellow the ablation threshold for sound tissue which, at the same time, can ablate and remove the carious tissue (Niemz, 2004;Strassl et al, 2008). In this way, the selective removal of carious tissue could be seen as a minimal intervention that does not depend on the professional experience, but essentially relies on the tissue chemistry (Serbin et al, 2002).…”

“…Considering the advances in technology for the development of ultra short pulse lasers (USPLs) (Niemz, 1995;Strickland & Mourou, 1985), efforts have been implemented to understand their interaction with dental hard tissues and to determine safe and proper parameters to provide a future clinical application in dentistry (Altshuler et al, 1994;Freitas et al, 2010;Kruger et al, 1999;Lizarelli et al, 2008;Strassl et al, 2008). Due to the extremely short pulse length, these systems promote precise cutting and have a strong potential for obtaining well-defined cavities and controlled caries removal (Niemz, 2004;Serbin et al, 2002).…”