Laser method for processing microcapsules or particles

Abstract: A radiating processing pulse laser together with a trapping laser is used to perform the modification and processing of particles and microcapsules. By using such methods, a reaction group, enclosed in a microcapsule, is caused to be released by imploding the micro capsule permitting specified reaction and processing. A miscroscope system is described.

Description: The present invention relates to laser microprocessing. More particularly, it relates to laser microprocessing which permits easy and accurate chemical modification and processing of the surface of a microparticle or a microcapsule through the radiation of laser beams, and further to a fine processing using these microparticles and microcapsules and the application thereof in the field of electronics, chemical engineering or medicine, etc. During recent years, attention has been focused on the development of fine modification and microprocessing technology thereof of chemical materials, such as high-molecule materials and inorganic substances, on a particle level. Aggressive research and development work has been in progress on this subject in the hope that such technology will be able to manipulate the elementary process of conversion process. Also in living cells, microprocessing designed to perform the transplantation, migration, fusion and other fine manipulation thereof has become very important. Conventionally, various methods by chemical manipulations have been proposed for such microparticles. But with chemical methods, it was exceedingly difficult to control the reaction between particles to be processed and the reaction processing agent, and there was a limit in precision to performing manipulations of particles one by one. On the other hand, in the field of manipulation of living cells, it has been possible to perform a migration process by manual methods, such as a fine injection process, and hence it has become possible to improve the manifestation efficiency to approximately 10 2 . However, by this method, the manipulator performs the processing by bringing a micropipette in direct contact with individual cells under a microscope. Hence, it becomes indispensable for such processing to be made within a clean bench, and such processing cannot be made automatic. For this reason, processing efficiency and processing amount depend on the skill and labor of the manipulator, and it is difficult to perform accurate processing in a short duration of time. Against the conventional method as described above, a processing method using laser beams to perform micromanipulation of particles has been proposed. Laser Focus, Vol. 18, No. 8, Aug. 1982, pages 22-26 discloses the trapping of particles using laser irradiation. Applied Physics Letters, Vol. 24, No. 12, 15 June 1974, pages 586-588 discloses the trapping of particles with laser radiation and the use of such a technique in holding particle targets in laser fusion in air or vacuum. Laser light is excellent in homogeneousness, directivity, luminance and controllability. And hence light energy can be concentrated and radiated on the fine regions of particles, and it becomes possible to perform non-contact accurate localized microprocessing which has been impossible by the conventional method. For instance, as a cell processing method using laser beams, a method has been proposed for collecting Ar laser beams with a system of lenses, adjusting the portion of particles to be radiated with the locating device of the microscope stage and radiating the same. The effect on cells and other particles can be varied by varying the wavelength of laser beams to be radiated, and hence attempts are being made to use laser beams. As a fine processing method using laser beams, a pattern-transfer in which laser beams are radiated, on a substrate through a photomask is known as an important process in semi-conductor fields. However, in the conventional methods, there have been limitations to the selection of radiation conditions, including the wavelength of laser beams, spot size diameter, pulse width and number of shots and a resolution as poor as the order of micron can be expected. It was impossible, for this reason, to improve the precision of fine and micro processings with laser beams. By the conventional method, not much has been known about the radiation of laser beams and the behaviour control of particles. For example, the technology for chemical modification and processing at particles has not been established, and the particle-locating precision has been poor and far from practical. EP-A-0 137 504 discloses the use of a pulsed laser to temporarily modify living biological cells in a liquid medium so that they may be implanted with a foreign substance. EP-A-0 307 940 describes the non-destructive trapping of biological particles suspended in a liquid medium such as water, using an infra-red trapping laser. Applied Physics B. Photophysics and Chemistry, vol.B46. no.3, July1988, Heidelberg DE, p.221-236: J.Wolfrum discloses the use of a pulsed UV laser to manipulate biological particles. The present invention has been made considering the foregoing circumstances, and has an objective of providing a new device and process which radiates laser beams onto particle sample as precisely as the order of micron, and the modification and processing of particles can be performed to a high precision. To solve the above problems, this invention provides a process for the microprocessing or micro-modification of microparticles characterised by trapping said microparticles, which microparticles are dispersed in a water or organic compound dispersion medium, by laser irradiation from a first source and processing or modifying the trapped particles by pulsed laser irradiation from a second source. Using the invention one may shift a microcapsule trapped by the radiation of laser beams and radiating processing laser beams for implosion, and perform chemical modification and processing at a required location with the reaction substrate released by said implosion. In this invention one may use a microscopic microspectroscope which is characterized by being equipped with an excitation pulse laser as well as a trap laser to determine the reaction characteristics of the phenomena that provide the basis for these microprocessings. In the accompanying drawings: FIG. 1 is a block diagram of one example of the small-sized device for microprocessing according to the present invention. FIGS. 2 (a), (b) and (c) are drawings illustrating the states of particles through the radiation of laser beams which indicate embodiments of the invention. FIGs. 3 (a), (b) and (c) are drawings illustrating the states of implosion of a micro capsule as embodiments of the invention. FIG. 4 is a measurement spectrum drawing by microscopic spectroscopy of this invention. What we call phototrapping, one of the features of microprocessing of this invention attracts attention as one of the manipulations on particles, and uses outstanding coherent characteristics possessed by laser beams to transfer the momentum which light has as a dynamic momentum that exerts upon a body and applies force to particles to trap or shift the body. By this phototrapping manipulation, only the force brought by laser beams acts upon an object, making possible a fully non-contact and non-destructive manipulation. In addition to such a trapping laser, the present invention uses a processing pulse laser. This laser processing is designed to perform modification, processing and other manipulations to the trapped particles under the required conditions. The most typical and important manipulations in the invention include the decomposition, division, local conversion, and chemical modification of particles, the connection and fusion between particles, and crosslinking with functional reaction groups. Great expectations are placed on this phototrapping technology as operations on microparticles. Here is a description of the principle of phototrapping. A laser beam enters particles through a lens, and is reflected and refracted, and the momentum possessed by the laser is delivered to the particle. Since the reflection rate is normally low, the momentum delivered by refraction becomes prevailing, and the force exerted thereby is transmitted to the particle. The particle is brought into being trapped by the laser. Accordingly, when the laser beam is caused to move, the particle follows the movement. As is evident from this principle, the manipulations such as non-contact and non-destructive trapping and shifting of particles become possible, and if the particle, for instance, polymer particles, on living cells and bacteria are subjected to modification and processing, this phototrapping becomes a very useful means in the reaction manipulation of microparticles. One of the characteristic forms of the present invention adopts the foregoing laser beams trapping means. FIG. 1 is a block diagram illustrating an example of a small-sized device for microprocessing according to the present invention. As is shown in this figure, the device of the invention possesses laser devices (A 1 ) (A 2 ), fine positioning device of laser radiation portion (B) and an image processing device (C). The laser device (A 1 ) constitutes a device for a very compact phototrapping device as microscopic system. This device makes it possible to manipulate microparticles easily and smoothly. The laser devices (A 1 ) (A 2 ) permit the selection of a laser source and the optical system thereof according to the type and size of particles involved and the purpose of necessary modification and /or processing. The laser device (A 2 ) radiates pulse laser beam which is used to provide modification and/or processing with the microcapsule trapped. The processing laser implodes the trapped micro capsules, permitting the modification and processing under specified conditions. By using such a method of implosion, the reaction group is caused to be released by imploding the micro capsule with the reactive group enclosed to implosion, permitting specified reaction and processing. It becomes possible, for example, to cause these reactions at the fine regions of a surface substrate. This invention is applicable to various particles, including organic polymer, the latex thereof, inorganic particles, metallic particles, or micro capsules. When particles are allowed to disperse in a dispersion medium, the dispersion medium may be water, alcohol, ether, and other various organic compounds. Some embodiments will be shown to further describe microprocessing and the device therefor. Embodiment 1 In a construction of the device as indicated in FIG. 1, polymethyl methacrylate (PMMA) latex particles are trapped and radiated by pulse laser for the reforming and local conversion of particles. The diameter of PMMA particles at this time was approximately 5 to 10µm. 1064nm (CW) and 355nm (pulse) laser beams from Nd:YAG laser as indicated in FIG. 1 were allowed to enter a microscope, and particles were trapped with the 1064nm (CW) laser beam, and PMMA particles were processed with the 355nm (pulse) laser beam. FIGs. 2 (a), (b) and (C) indicate the status of particles in a single, a two-time and multiple shots of pulse light. In the particle (1) trapped, a processed portion (2) is generated presumably due to the fact that PMMA crosslinking is severed, and the processed portion (2) is expanded by multiple shots. Ablation at 1Hz is shown. The result shows the possibilities of trapping, and the modification and processing of particles, with laser, and it is expected that the laser beam will find more applications when used with use of multiple kinds of particles. Embodiment 2 Table 1 shows the laser trapping made using the fundamental wave (1064nm) of cwNd 3 :YAG laser. It shows that the refractive index of polystyrene latex, PMMA latex, liquid paraffin droplets and other particles is larger than that of the surrounding medium thereof. They are trapped as is indicated by the principle. However, it could be observed that in the water droplets in liquid paraffin, the relationship of refractive index is inverted and water the droplet moves out from the focus of the laser. When the diameter of particles was larger than a laser spot (-1µm), they could be trapped three-dimensionally, but when their diameter was smaller than the laser spot, the force acting in the direction of laser light axis (Zaxis) became exceedingly small. In such a case, the particles could be manipulated two-dimensionally on a glass plate at the bottom of the sample cell. Though the particles of oxidated titan (titanium) were not spherical, they could be trapped two-dimensionally. Laser Trapping of Various Particles Medium(Refractive Index) Particle(Refractive Index) Trapping Water(1.33) PMMA Latex(1.49) Yes Polystyrene Latex(1.59) Yes Toluene Droplet(1.50) Yes Liquid Paraffin Droplet (1.46∼1.47) Yes Titanium dioxide Yes Salmonella Typhymurium Yes Ethylene glycol(1.43) PMMA Latex(1.49) Yes Polystyrene Latex(1.59) Yes Diethylene glycol(1.45) PMMA Latex(1.49) Yes Polystyrene Latex(1.59) Yes Liquid Paraffin(1.46∼1.47) Water Droplet(1.33) No Embodiment 3 After a non-spherical microcapsule with a diameter of 10µm was trapped by laser, a pulse laser (355nm, 7ns fwhm) was radiated to cause implosion. The results are shown in FIGs. 3. FIG. 3 (a) indicates the state where the microcapsule (3) was trapped with laser. The strength of laser light used for the trapping is 3.2W. It was confirmed that this microcapsule (3) was trapped three-dimensionally by shifting the stage of a photomicroscope. FIG. 3(b) indicates the state after 41.7J/cm 2 of pulse laser are radiated on the microcapsule (3) trapped in a single shot. Though no implosion of the capsule was observed, it can be confirmed that the capsule was transformed with the radiation of pulse lasers. In addition, when 1.37kJ/cm 2 was radiated in a single shot, an implosion of the capsule (3) occurred, and the toluene solution (4) in a pyrene of content solution was ejected into the outer water phase (FIG. 3-c). It was round that at that time, the toluene solution (4) ejected into the water phase is spherical and that this is trapped with laser. Using this technology, a microcapsule in which a reaction group in contained is transported to a given place of an electrode subjected to fine processing, and only a spacial region at and near the electrode as small as micron order can be chemically modified by the radiation of another excitation laser light. Embodiment 4 In a construction as indicated in FIG. 1, the latex used to dope the pyrene was trapped, and subjected to the radiation of pulse laser for the excitation of the particles. The diameter of the particles of PMMA at this time was approx. 5 to 10µm. 1064nm (CW) and 355nm (pulse) low-energy laser beams from the Nd:YAG laser were entered into a microscope, the particles were trapped with the 1064nm (CW) laser beam, and the particles were excited with the 355nm (pulse) laser beams. It becomes possible to trace the time-resolved spectrum and reaction species from the light emission due to this excitation. FIG. 4 indicates the spectra of the wavelength and strength of the emitted light. The result shows the possibilities of trapping and spectrochemical analysis with laser, and its application in particle analyses is expected to expand. Liquid paraffin solution (1X10 2 mol dm 9 ) as pyrene was allowed to disperse in water, and the fluorescent light of the micro droplet thereof was measured, The results obtained by subjecting the 3.6µm droplet to laser trapping and spectrochemical analysis were shown in FIGs. 5 and 6. The figures show that the fluorescent spectrum was found to indicate the vibrational structure peculiar to the pyrene in the vicinity of 370 and 400nm, and the band of excimer having its maximum wavelength in the vicinity of 470nm, and also that it was possible to identify trapped particles. Moreover, the damping and rise was able to be observed. Similar measurements could be observed in a polymer latex in which a pyrene, p-tarphenil , and other fluorescent pigments are doped.

Claims: A process for the microprocessing or micromodification of microparticles characterised by trapping said microparticles, which microparticles are dispersed in a water or organic compound dispersion medium, by laser irradiation from a first source and processing or modifying the trapped particles by pulsed laser irradiation from a second source. A process as claimed in claim 1 wherein the trapped microparticles are caused to move to a specified location and subjected to pulsed laser irradiation from said second source. A process as claimed in claim 1 or claim 2 wherein said microparticle is a microcapsule which is caused to implode by said pulsed laser irradiation from said second source. A process as claimed in claim 3 wherein said microcapsule encloses a reaction group, and said microcapsule is caused to implode by said pulsed laser irradiation from said second source so as to cause chemical modification of said reaction group. A process as claimed in claim 1 or claim 2 wherein the process comprises micromodification or microprocessing of a species by varying the energy of a single laser or controlling the energy of radiation of multiple wavelengths. A process as claimed in claim 1 or claim 2, wherein the trapped microparticles and a chemical species on the surface and/or inside thereof are excited to emit light for spectrometry.

Inventors: KITAMURA NOBORU, KOSHIOKA MASANORI, MASUHARA HIROSHI, MISAWA HIROAKI, SASAKI KEIJI, KITAMURA, NOBORU, KOSHIOKA, MASANORI, MASUHARA, HIROSHI, MISAWA,HIROAKI, SASAKI,KEIJI, SASAKI,KEIJI, 14-20-405, SHOAZA-TORIIMAE
Applicants: JAPAN SCIENCE & TECH CORP, JAPAN SCIENCE AND TECHNOLOGY CORPORATION
Application year: 1990
Main classification: H01S3
IPC codes: B01J19, G01N21, B01J13, B23K26