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A Rapid Laser Probing Method Facilitates the Non-invasive and Contact-free Determination of Leaf Thermal Properties

Plants can produce valuable substances such as secondary metabolites and recombinant proteins. The purification of the latter from plant biomass can be ...

Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e. V.

Calcium phosphate (CaP) coatings are used for obtaining a desired biological response. Usually, CaP coatings on metallic substrates are crystallized by annealing at temperatures of at least 400-600 degrees C. For polymeric substrates, this annealing is not possible due to the low melting temperatures. In this work, we present a more suitable method for obtaining crystalline coatings on polymeric substrates, namely laser crystallization. We were successful in obtaining hydroxyapatite coatings on polyethylene. Because of the UV transmission characteristics of the CaP coatings, the use of a low wavelength (157 nm) F(2) laser was necessary for this. As a result of the laser treatment, the CaP coating broke up into islands. The cracks between the islands became larger and the surface became porous with increasing laser energy. The mechanism behind the formation of this morphology did not become clear. However, the fact that crystalline CaP coatings can be obtained on polymeric substrates in an easy way, possibly allows for the development of new products.

Laser-induced crystallization of calcium phosphate coatings on polyethylene (PE).

We evaluate the feasibility of nanosecond-pulsed and femtosecond-pulsed lasers for otologic surgery. The outcome parameters are cutting precision (in micrometers), ablation rate (in micrometers per second), scanning speed (in millimeters per second), and morphological effects on human middle ear ossicles. We examine single-spot ablations by a nanosecond-pulsed, frequency-tripled Nd:YAG laser (355 nm, beam diameter 10 microm, pulse rate 2 kHz, power 250 mW) on isolated human mallei. A similar system (355 nm, beam diameter 20 microm, pulse rate 10 kHz, power 160-1500 mW) and a femtosecond-pulsed CrLi:SAF-Laser (850 nm, pulse duration 100 fs, pulse energy 40 microJ, beam diameter 36 microm, pulse rate 1 kHz) are coupled to a scanner to perform bone surface ablation over a defined area. In our setups 1 and 2, marginal carbonization is visible in all single-spot ablations of 1-s exposures and longer: With an exposure time of 0.5 s, precise cutting margins without carbonization are observed. Cooling with saline solution result is in no carbonization at 1500 mW and a scan speed of 500 mms. Our third setup shows no carbonization but greater cutting precision, although the ablation volume is lower. Nanosecond- and femtosecond-pulsed laser systems bear the potential to increase cutting precision in otologic surgery.

Morphological effects of nanosecond- and femtosecond-pulsed laser ablation on human middle ear ossicles.

Patent ductus arteriosus (PDA) size and morphology influence the selection of the kind and the size of the embolization device used to effect shunt closure.

Transthoracic echocardiographic measurement of patent ductus arteriosus in dogs.

The functional analysis of plant cells at the cellular and subcellular levels requires novel technologies for the directed manipulation of individual cells. In this report, we demonstrate the use of an infrared (1,064 nm) picosecond laser for the perforation of tobacco cell protoplasts. A single pulse was sufficient to perforate the plasma membrane enabling the uptake of dye from the surrounding medium into the cytosol. Moreover, the procedure was shown to be suitable for the efficient delivery of DNA expression constructs to the nucleus, as demonstrated by the subsequent expression and correct targeting of a recombinant fluorescent protein. Single cell perforation using this novel optoporation method shows that isolated plant cells can be permeabilized without direct manipulation. This is a valuable procedure for cell-specific applications, particularly where the import of specific molecules into plant cells is required for functional analysis.

Infrared picosecond laser for perforation of single plant cells.

To assess the feasibility of magnetic resonance (MR)-guided delivery of a solution containing contrast-medium and immediate online monitoring of its distribution to the vessel wall during MR-guided angioplasty in peripheral arteries.

Magnetic resonance-guided angioplasty with delivery of contrast-media doped solutions to the vessel wall: an experimental study in swine.

To evaluate the percutaneous angiography and the morphology of patent ductus arteriosus (PDA) in dogs.

Percutaneous angiography of Patent Ductus Arteriosus in dogs: techniques, results and implications for intravascular occlusion.

Collagen scaffolds are popular for the reconstitution of dermal equivalents. Usually, these scaffolds are fixed with sutures or staples and in many cases these devices have to be removed in a second procedure. Laser-mediated tissue welding in a wet environment is a potential alternative for collagen scaffold fixation and may be advantageous to suture, staple, and tissue glue fixation.

Laser-mediated fixation of collagen-based scaffolds to dermal wounds.

This study aimed to evaluate the possibility of introducing ultra-short pulsed lasers (USPL) in restorative dentistry by maintaining the well-known benefits of lasers for caries removal, but also overcoming disadvantages, such as thermal damage of irradiated substrate. USPL ablation of dental hard tissues was investigated in two phases. Phase 1--different wavelengths (355, 532, 1,045, and 1,064 nm), pulse durations (picoseconds and femtoseconds) and irradiation parameters (scanning speed, output power, and pulse repetition rate) were assessed for enamel and dentin. Ablation rate was determined, and the temperature increase measured in real time. Phase 2--the most favorable laser parameters were evaluated to correlate temperature increase to ablation rate and ablation efficiency. The influence of cooling methods (air, air-water spray) on ablation process was further analyzed. All parameters tested provided precise and selective tissue ablation. For all lasers, faster scanning speeds resulted in better interaction and reduced temperature increase. The most adequate results were observed for the 1064-nm ps-laser and the 1045-nm fs-laser. Forced cooling caused moderate changes in temperature increase, but reduced ablation, being considered unnecessary during irradiation with USPL. For dentin, the correlation between temperature increase and ablation efficiency was satisfactory for both pulse durations, while for enamel, the best correlation was observed for fs-laser, independently of the power used. USPL may be suitable for cavity preparation in dentin and enamel, since effective ablation and low temperature increase were observed. If adequate laser parameters are selected, this technique seems to be promising for promoting the laser-assisted, minimally invasive approach.

Precise ablation of dental hard tissues with ultra-short pulsed lasers. Preliminary exploratory investigation on adequate laser parameters.

To evaluate the suitability of an ultra-short pulsed laser (USPL) to treat zirconia ceramic surfaces and increase their adhesion to dual-curing resin cement.

Martin Wehner

Fraunhofer Institute for Laser Technology ILT

Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e. V.

A Rapid Laser Probing Method Facilitates the Non-invasive and Contact-free Determination of Leaf Thermal Properties