Jan 17, 2018 | By David
A team of researchers in Switzerland have recently made a remarkable new breakthrough that could suggest a bright future for the field of 3D bio-printing. They developed a new endoscopic SLA technique, which makes use of an ultra-fine optical fiber to focus a laser beam, in order to create structures on a very small scale. This innovative approach could one day be used to print bio-compatible structures directly into tissue inside the human body, with the potential to repair damage, as well as a range of other crucial applications.
A range of laser-based 3D microfabrication techniques already exist, but most current methods rely on complicated laser equipment that can be prohibitively expensive as well as excessively bulky. These methods make use of an optical phenomenon known as two-photon polymerization, whereas the new approach takes advantage of a different phenomenon in which a specific chemical’s solidification only occurs above a certain threshold in light intensity.
(two-photon laser equipment)
According to research team leader Paul Delrot, from École Polytechnique Fédérale de Lausanne, Switzerland, "Our group has expertise in manipulating and shaping light through optical fibers, which led us to think that microstructures could be printed with a compact system. In addition, to make the system more affordable, we took advantage of a photopolymer with a nonlinear dose response. This can work with a simple continuous-wave laser, so expensive pulsed lasers were not required’’
(structures made using two-photon polymerization)
The relatively cheap, continuous laser beam that the team used emitted light at a wavelength of 488 nanometers. This is within the range of visible light and is much safer for human cells than other types of lasers. They focused the beam through a tiny optical fiber, which enabled the targeted solidification of specific areas of a droplet of light-sensitive liquid. This is a similar approach to the stereolithography 3D printing method, but on a much smaller scale. The photo-polymer used was made from an organic polymer precursor combined with a photo-initiator, and it was created from chemicals that are affordable and readily available.
The calibration of the laser equipment before the microfabrication process enabled the light to be focused without having to move the optical fiber at all. Hollow and solid micro-structures were created in the photo-polymer to a high degree of precision, with a lateral (side-to-side) printing resolution of 1 micron and an axial (depth) printing resolution of 21.5 microns. The success of this approach means that it could soon be used for studying how cells interact with various microstructures in animal models, eventually paving the way for endoscopic 3D printing in people.
(structure created using the new low-power, fiber-focused technique)
"With further development our technique could enable endoscopic microfabrication tools that would be valuable during surgery...These tools could be used to print micro- or nano-scale 3D structures that facilitate the adhesion and growth of cells to create engineered tissue that restores damaged tissues’’, said Delrot. "Compared to two-photon photopolymerization state-of-the-art systems, our device has a coarser printing resolution, however, it is potentially sufficient to study cellular interactions... Since our approach doesn't require complex optical components, it could be adapted to use with current endoscopic systems."
The results of the research were published in a paper entitled "Single-photon three-dimensional microfabrication through a multimode optical fiber," in the journal Optics Express. The next stage for the team, on their journey towards surgical implementation of their pioneering technology, is to develop a new photo-polymer chemical that is bio-compatible. They also need to create a compact delivery system for this material. Another requirement is a faster scanning speed, but this limitation could be potentially overcome by using a commercial endoscope instead of an ultra-thin fiber, as the size of the instrument would not necessarily be relevant in all applications. The team also needs to develop a technique to finalize and post-process a printed micro-structure inside the body, so that it is suitable for bio-medical functions.
Posted in 3D Printing Application
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