SE469206B - PROCEDURE TO CUT GROWTH MATERIALS FOR MICRO-INCREASING GROWTHS USING A PULSED LASER RADIATION - Google Patents

Description

469 206 The fragile plant material can also be easily damaged by the cut.

Cutting with a knife is slow, especially when operating with lightly contaminated material, where special attention should be paid to aseptics.

It has now surprisingly been found that the above-mentioned problems can be reduced by using a pulsed laser beam for cutting the plant material.

Living tissue has previously been cut with a laser beam only in connection with surgery. The advantage of using a laser beam in surgical operations can be considered to be that the blood vessels of the tissue are burned and the operation is facilitated as the bleeding is prevented, in particular from small blood vessels. On the other hand, it was unexpectedly observed in connection with this invention that the guide strands of the plant material are not damaged by laser cutting, but the cell tissue retains its water and nutrient uptake ability via the cut surface and in addition the totipotency of the cell tissue is maintained near the cut area.

Additional advantages of laser use for cutting plant material are ease of handling and speed. Due to the high aseptic requirement, when working with plant material, the knife should usually be sterilized between each incision, by wetting it in ethanol and by flaming. This delays the cutting and ethanol can end up in the plant material, which even in small amounts causes a delay in growth or can result in the plant withering. Sterilization can also be done by heating the instrument. On the other hand, the laser beam is naturally sterile, which significantly enhances the aseptic. The average speed increases at the same time, as the sterilization phase ceases.

Laser cutting can also be combined with automation. Then the proportion of manually performed work is small and the cutting is noticeably accelerated. 469 206 When laser cutting, the damage to the plant material is mainly due to heating. To improve the average result, inert shielding gases such as nitrogen, carbon dioxide or argon are used. The shielding gas is led to the point to be cut in open space with a nozzle or alternatively the cutting is performed in a chamber filled with shielding gas.

The amount of shielding gas is chosen so that there is as little charring as possible.

In connection with the present invention, a laser device whose main parameters are described below is used for cutting plant material.

The modal value of the laser device indicates the form of distribution of its beam. In the cutting test, a continuous TEM 00 was used as the function modal value, whereby the intensity of the beam is distributed according to Gauss' bell-shaped curve.

The cutting device's cutting capacity indicates how much energy the device is able to move per unit time to the point to be cut.

Often the entire effect is not absorbed in the cut point but is reflected from the surface of the point and / or absorbed in vapors and gases emanating from the point. The cutting capacity can also be specified using the intensity, which indicates the beam of the cutting capacity per surface. As the focusing lens directs the beam at a very small area in the focal point, even with a small cutting capacity, high intensity values can be achieved. The tests have shown that it is possible to cut plants with a CO laser with an output of only 20 W, but the cutting speed is then not sufficient. It has been stated in the literature that an effect of approx. 40 W is sufficient to cut living animal cell tissue. On the other hand, the price of the laser device rises almost proportionally to the power of the second power, so that the highest power of the economically justified laser device is 100 W.

Accordingly, the power of the suitable laser device according to this invention should be between 30-100 W.

When pulsing the laser beam, the pulse length and the time values between the pulses should be chosen so that the cut material is heated as little as possible. Values between 0.1-10 ms are suitable.

The beam diameter at the focal point also affects the cutting result, but in general this parameter is constant and of the size class 0.2 mm or less.

In the following examples, CO (Coherent) longitudinal flow lasers are used as cutting lasers, whose beam modal value is TEM OO and resonator equipped with ECQ module, which enables pulsation of the beam. The continuous power of the laser device could in principle be controlled in the range 90-350 W, but for the cutting sample they wanted to reduce the power with a special gas mixture, whereby the constant continuous power was 61 W. The pulse frequency could be selected in the range c.10-2500 Hz and the length of the individual laser pulse in the range 0.1 ms-10 s. The beam diameter at the focal point was c. 0.2 mm. Nitrogen with a purity of 99.998% was used as the shielding gas. The workstation consisted of an xy table, which had the dimensions 600 x 600 mm.

Example The tests were performed on birch. The consequences of the cutting were observed with the help of reproduction tests and subsequent greenhouse cultivation.

As the laser beam heats the cut point, the plant cell tissue may dry out or burn during charring. Injuries to the incision surface were observed under a microscope. If an excessive effect was directed towards the cut surface, it was often expressed as charring and shrinkage of the joint strands, ie the "melting" of the cell tissue.

By changing the parameters of the device, an attempt was made to improve the cutting result.

For cutting, the plant parts were attached with sterile small petri dishes filled with agar (9 g / l). 469 206 Birch, Betula pendula Birch shoots (from in vitro stands) were laser cut into pieces that contained a leaf fold bud. Control tests were performed by cutting the shoots with a knife. The buds were placed on the reproduction substrate and grown in culture cabinets (23 C, humidity 50%, light 2000 lux, 16/6 h). Two parallel tests were performed (3-7 shots per test).

The growth of the inoculums was monitored and the reproduction coefficient was calculated twice, 4 and 6 weeks after the transfer. During the laser cutting, the parameters in Table 1 were tested.

Table 1. Alternative parameters tested in laser cutting of birch.

Cutting method no. Pulsation parameters Max. Velocity Average Tp / ms Te / ms T / ms f / Hz% lm / s power / W l 0.1 0.4 0.5 2000 0.5-0.6 15.5 2 0.1 0 .7 0.8 1250 0.4-0.5 10.5 3 0.1 1.0 1.1 909 0.2 8.5 5 1.0 1.0 2.0 500 2.0 33 6 1 .0 10 11 91 0.2 12 7 10 10 20 50 0.6 32 8 continuous power 2.4 61 The laser-cut grafts were well reproduced. The reproduction of birches cut in different ways after 4 and 6 weeks of cultivation is shown in Figure 1.

The pulse length (Tp) was maintained at 0.1 ms in sections 1-3, but the return phase (Te) varied. When cutting with method no. 1, the resting stage between the pulses was 0.4 ms and with method no. 2 it was 0.7 ms.

The average speed could be kept almost equal in each. The longer 469 206 return phase appears to improve the viability of the cell tissue, which was marked as an increased coefficient of reproduction. The reproduction seemed more efficient with the cutting methods 5, 6 and 7. For the fifth test subject, the long pulse (1.0 ms) and the fairly long pause (1.0 ms) gave a good result in fast operation (2% / ms). An extension of the pause to 10 ms at the expense of the operating speed gave the same reproduction result in sample no. 6. Provindivid no. 7 surprisingly gave the best growth result: there the very long pulse (10 ms) and very long pulse intervals (10 ms) were combined at a reasonable operating speed (0.6% / ms-).

With continuous power, 61 W (individual no. 8), the cut cell tissue appeared to be reproduced on average worse than a cell tissue cut with a pulsed beam.

On the basis of the sample, it can be considered that laser is well suited for cutting birch. Reproduction was at least as effective as with a knife incision. The birches normally took root after reproduction after laser cutting. The best reproduction was achieved with the pulsation in sample no. 7, where it is assumed that the long return time prevented the cell tissue from heating and burning too much. On the basis of the sample, it can be concluded that a laser that vibrates with a small frequency damages the plants the least (method 7).

Claims (5)

f'469 206 Patentlmav Method for cutting plant material for micro-oiling of plants, characterized in that the learning is not carried out by heating the pulsed laser beam. 2. Procedure claim 1, characterized in that the Cbz laser is used. 3. Procedurexl. claims or 2, characterized in that during pulsation the average power varies between 5 and 40 W. 4. Procedure according to any of the preceding claims, characterized in that lming objects to be cut are used as a shielding gas. 5. Procedurel. claim 4, characterized in that an inert gas, preferably nitrogen or carbon dioxide, is used.