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Micro Droplet technology

Micro Droplet technology

Micro Droplet Platform Technology

In recent years, microdroplet generation technology has been widely used in chemistry, medicine, pharmaceuticals, and electronic engineering. For several decades, the microdroplet generation technology based on the twin-fluid spray and the droplet-on-demand (DOD) technique has been applied for applications such as inkjet printing, spray coating, and metering injection.  However, existing microdroplet generation technologies have a few disadvantages from the viewpoint of variation in droplet size and speed. In the case of twin-fluid sprays, the diameter and speed of the droplets ejected from the nozzle have a high standard deviation of approximately 20%. The droplet diameter ranges between a few micrometers and a few hundred micrometers. The variation in the droplet speed is also similarly large. Generally, the twin-fluid spray nozzle ejects numerous high-speed droplets but with large variation in size. Meanwhile, droplets released from the DOD-type nozzle have low diameter and speed variations, but very low speed. Comparing with existing methods, the strength of our technology is that precise and massive  microdroplets for a very short time can be produced with extremely low variation in diameter and speed. As shown in Fig. 1, the standard deviation of the droplet diameter and speed can be controlled within 2%. This is a dramatic and innovative result that has not been achieved thus far through conventional technology. Fig. 1 shows the images of the dispensed microdroplets and the characteristics of the droplets as captured by a high-speed camera.

The discontinuous droplet series appear to be similar to a continuous stream of liquid, as shown in Fig. 1(a). A zoomed image of an individual liquid stream captured by the high-speed camera shows the microdropl et behavior in detail Fig. 1(b).

Micro Droplet Generation System

This innovative microdroplet generation system consists of a liquid supply system and control software, and especially, a nozzle body manufactured by micromachining technology. As shown in Fig. 3, the liquid supply system is composed of a high-pressure metering pump, valves, a pressure gauge, and a flow meter. The entire system is operated by a pumping motor and sequence control software. In addition, a high-speed vision system using image processing that is optimally designed to capture microdroplets measures the diameter and speed of the droplets.

We can provide customers with a complete package of the microdroplet generation system, including the sub-systems, i.e., the chemical supply, droplet ejection nozzle, and droplet measurement system. Fig. 4 shows our typical models of micro-droplet generation system, The desk-top models is made for the purpose of research use in the academy or in the institution. The stand-alone model is the back-bone for mass production in the company. According to the request of the customer, we adds several option like as the spin chuck, the heating plate, the bowl type collector, and so on.

The nozzle system consists of a nozzle body, a piezo-actuator, and an ultrasonic generator, as shown in Fig. 5. A few hundred microholes of size ranging 5mm to 50mm can be accurately drilled on the nozzle body using a micromachining technology with a nanosecond laser source. The nozzle body can be made of ceramics (e.g., quartz or sapphire), engineering plastics (e.g., PEEK, PPS, PTFE, or PFA), or metal (e.g., steel or aluminum). The nozzle thus prepared can discharge a few millions of droplets per second because of the high-frequency vibration of the piezo-actuator. The specially designed ultrasonic generator sends voltage signals of more than 1MHz to the actuator. Fig. 6 show the assembly of micro-hole nozzle and ultrasonic generation system.


Semiconductor Wafer Cleaning

Since 2014, our microdroplet generation system has been installed above 200set inside the semiconductor single wafer cleaning equipment used in the SAMSUNG SYS.LSI Fab for 14nm FinFET process. The basic physics of wafer cleaning is that microwaves originating from the impact of the microdroplets with the liquid thin film on a wafer remove contamination particles, as shown in Fig. 7.


Precision Dispensing Coating

Since 2014, our microdroplet generation system has been installed above 200set inside the semiconductor single wafer cleaning equipment used in the SAMSUNG SYS.LSI Fab for 14nm FinFET process. The basic physics of wafer cleaning is that microwaves originating from the impact of the microdroplets with the liquid thin film on a wafer remove contamination particles, as shown in Fig. 8.

Emulsion

Emulsion is widely used technology in the pharmaceutical, cosmetic, and food industry. Conventionally, emulsion is generally produced by homogenizing after mixing aqueous and oil solution including pharmaceutical and functional materials. Emulsion is divided into the nano-emulsion and macro-emulsion. The nano-emulsion have the size ranging from 500nm to 10mm and The size of macro-emulsion has the range from 10mm to 5mm. The macro-emulsion can conserve in long-term the functional constituents that easy to oxidize because the bigger the size of emulsion, the more functional constituents can be confined. The conventional method based on the homogenizing chemicals needs much surface active agents for stabilizing the emulsion. On the other hand, our micro-droplet platform technology as shown in Fig. 9 can make forcibly initial emulsion with the size of tens of micrometer by dispensing oil droplets into aqueous solution. Therefore, we can reduce the use of the surface active agents necessary to the stable formation of oil drop. Generally, the surface active agents has a negative effect on the human skin and tissue. The micro droplet solution with minimizing the surface active agents is expected to a potential application in the pharmaceutical, cosmetic, and food industry.

Spraying Suspension Polymerization Process

(Magnetic Bead Production)

Magnetic polymer microspheres have been widely used in the fields of biomedical diagnostics and bioengineering such as in cell isolation,, protein separation and purification. Especially, suspension polymerization is the most suitable for mass production of magnetic polymer microspheres. Conventionally, the droplets of prepared oil phase were dispersed by the mechanical stirring method. The magnetic microspheres obtained, however, are not suitable for the biological application because of the inhomogeneity in size and magnetite content. Ugelstad developed in situ formation of iron oxide inside the preformed porous mono-disperse polymer particles produced by the activated swelling method, but the multistep process is very tedious with preparation of mono-disperse seed particles in the first step. As a result, the magnetic microspheres prepared by this method are rather expensive. Based on the micro-droplet generation platform, spraying suspension polymerization (SSP) process was proposed. Magnetic polystyrene microspheres with a narrow size distribution were prepared by the spraying suspension polymerization of styrene in the presence of Fe3O4 nanoparticles.