Automatic spin coating system

An automatic spin coating system includes a dispensing assembly and a base assembly. The dispensing assembly comprises a dispensing device that contains a coating material, a pulley assembly, a drive gear, and a smooth wheel. The base assembly includes a coating plate for receiving the coating material, a chuck plate for securing the coating plate, a stepper pin capable of engaging the drive gear of the dispensing assembly, and an electric motor for spinning the chuck plate. The dispensing device further comprises a vessel assembly to provide immobilization of the dispensing device, and a tubing assembly to control the flow of the coating material. The dispensing device is connected to the pulley assembly, which in turn is connected to the drive gear and the smooth wheel. When the chuck plate spins, the stepper pin revolves and touches the drive gear so as to rotate the pulley assembly, and meanwhile, the coating material is dispensed and coated on the coating plate in different circles without overlap between circles. In one embodiment, the stepper pin has a gear with different sizes of teeth that allow different degrees of movements of the dispensing device. The coating material is then dispensed from a first circle to a second circle.

FIELD OF THE INVENTION

The present invention relates to a spin coating device, and in particular, a device for automatically developing blood films.

DESCRIPTION OF RELATED ART

Analysis of blood film is an important laboratory test for clinical examination and diagnosis of various diseases. Blood smear is one type of blood film and has been widely used to examine the health and relative counts of blood cells. Blood smear is often prescribed to identify immature, abnormal, or diseased blood cells, and also monitor patients' undergoing treatments. Many diseases and disorders (including but not limited to cancers, anemia, bone marrow disorders, malaria, lymphoproliferative disease, liver failure, renal diseases, sepsis and etc.) can affect the status of blood cells in terms of their number, function, and lifespan. Additionally, symptoms of fatigue, unexpected or severe infection, bone pain, unexplained jaundice, sudden weight loss, skin rash and etc. can be diagnosed by blood smear.

Blood smears are typically prepared by placing a drop of blood over a microscope slide, and then a spreader slide is used to disperse the blood over the microscope slide. This technique develops the monolayered blood film with feathered edge for where blood cells are spread apart so that they can be differentiated and examined individually. With manual techniques, preparation of the blood smear can easily fail, causing irregular spread of blood with waves, holes, ridges, jagged tail, and damaged cells. Common causes of poor manual blood smear include the size of the blood drop being too large or too small, failure to keep constant contact between slides, failure to keep right angle between slides, failure to use uniform force across slides, and so on. Therefore, manual blood smear requires technical training and clinical experience and hardly prevents human errors during preparation.

Automated blood smearing can minimize human errors and be achieved by traditional spin coating, where at high spin speed (1,000-5,000 revolutions per minute; RPM), the coating material spreads over the substrate, spins off the edge, and forms a thin film on surface. Volatile organic solvent is typically used to dissolve the coating materials for low surface tension and high evaporation rate. The coating process is highly dynamic and out-of-equilibrium, causing topographic result of coated film not finely tunable. Coating defects like bubbles, comets, streaks, flares, swirl pattern, incomplete coating and pinholes are frequently observed. The powerful centrifugal force can also alter the morphology and affect the integrity of the coating materials. In addition, spin-off of excess coating materials from surface in the form of aerosol can be hazardous.

The object of the present invention is to improve traditional spin coating technology by overcoming its intrinsic defects and resolving its operational variations. This invention provides coating of uniform films with high reproducibility, preserves the intactness of coating materials, eliminates human errors, external contamination, and spin-off of excess coating materials, and facilitates computer aided target recognition and data interpretation. The present invention overcomes the aforementioned problems by employing an automatic spin coating system having a low spinning speed, a dispensing system mimicking the spreader slide, a translational mechanical system combining both angular and linear movements, and active bio-friendly temperature control for preservation of coating materials. Specifically, the design of the nozzle of the present invention will not only prevent common contaminations that often occur in manual blood smears, but also preserve the blood sample by only delivering the exact amount needed for the automatic coating process.

SUMMARY OF THE INVENTION

The present invention is a spin coating system that automatically dispenses a coating material on a coating plate. The spin coating system comprises a dispensing assembly and a base assembly. The dispensing assembly includes a dispensing device having a vessel (such as a tube) containing the coating material to be dispensed and a tubing assembly to deliver the coating material and control the flow. The dispensing device is connected to a pulley assembly, which in turn is connected to a drive gear and a smooth wheel. Before the drive gear is actuated, the dispensing device dispenses the coating material in a circle. When the drive gear is actuated, it drives the pulley assembly so as to move the dispensing device from a first position to a second position. In this way, the dispensing device can be moved to dispense the coating material in different circles.

The base assembly, located below the dispensing assembly, has a coating plate for receiving the coating material dispensed by the dispensing assembly. The coating plate is secured in a chuck plate that is capable of spinning and rotated by a motor. The chuck plate has a stepper pin located in a position to engage the drive gear of the dispensing assembly. When the chuck plate spins, the stepper pin revolves around the spin axis. As the stepper pin makes a complete revolution, it engages the drive gear of the dispensing assembly. This causes the pulley assembly to move the dispensing device such that the coating material is dispensed in different circles on the spinning coating plate.

The dispensing of the coating material at different circles on the coating plate can be controlled by a gear head on the stepper pin. In a preferred embodiment of the invention, the gear head on the stepper pin has different sizes, such that each size translates into a different degree of movement of the dispensing device when the stepper pin makes contact with the drive gear.

In one embodiment of the automatic spin coating system, there is provided a spin coating method. The chuck plate rotates by a motor. The dispensing devices moves from the first position to the second position by the pulley assembly, while discharging the coating material from the dispensing device toward the coating plate in different circles. The dispensing device moves when the drive gear is rotated by the stepper pin, which causes the different movement of the dispensing device. The coating plate spins with the chuck plate such that the coating material is dispensed on different circles of the coating plate.

These and other objects, advantages, and features of the invention will be more fully understood and appreciated by reference to the detailed description of the current embodiments and the drawings.

DETAILED DESCRIPTION OF EMBODIMENTS

An automatic spin coating system, shown inFIGS. 1A and 1B, is comprised of a top housing100and a bottom housing110.FIG. 2Aillustrates a dispensing assembly20inside of the top housing100. The dispensing assembly20is capable of dispensing a coating material202to a coating plate222located in the bottom housing110.

The automatic spin coating system10can be used for coating a variety of coating materials202, including but not limited to biospecimens (including human specimens and body fluids, such as whole blood, blood plasma, blood serum, saliva, urine, bone marrow, cerebrospinal fluid, pericardial fluid, pleural fluid, umbilical cord blood, milk, and etc., whether raw or diluted, original or derived products for clinical research, examination, detection and diagnosis; and cell cultures, culture media, biologic production media, lysate, eluate, extraction, fermentation media, brewing media, and etc. for laboratory examination of activity, viability, secretion, excretion, expression, and morphology involving, relating to, or derived from living organisms) and biological and non-biological, organic, inorganic and polymeric, fluids, solutions, dilutions, sols, gels, emulsions, solvents, mixtures, suspensions, colloids, and etc.

FIGS. 1A and 1Billustrates an automatic spin coating system10comprising a top housing100and a bottom housing110. The top housing100and a bottom housing110are enclosed together. Referring toFIGS. 1C and 1E, the top housing100has two transparent windows102,104for inspection of the coating process. Window102is on top of the top housing, and window104is on side of the top housing. The top of the top housing100, as shown inFIG. 1D, further has a LED display108and a control panel106. In one embodiment, the control panel108has three parameters that allows users to manually control the coating process, including spin speed, substrate surface temperature and coating time.

Referring toFIGS. 2A and 2B, the automatic spin coating system10has the dispensing assembly20inside the top housing100. The dispensing assembly20is comprised of a dispensing device26, a pulley assembly24, a drive gear214and a smooth wheel220. The dispensing device26is connected to the pulley assembly24, which in turn is connected to the drive gear214and a smooth wheel220. In one embodiment, the dispensing device26has a vessel204, held by a vessel holder206connected to an adaptor208that contains one or more sliding housings211. The vessel204contains the coating material202to be dispensed from the dispensing device26from a first position to a second position. The vessel204can be a tube or a container. Also, referring toFIGS. 2A and 2B, the base assembly22is housed inside the bottom housing110. The base assembly22is comprised of a coating plate222for receiving the coating material202, a chuck plate224for securing the coating plate222, and a stepper pin216. The coating plate222can be a round substrate, for example, a glass disc. Referring toFIGS. 2C and 2F, the stepper pin216is mounted on the chuck plate224that is capable of engaging the drive gear214of the dispensing assembly20. The drive gear214is touched and rotated by the stepper pin216that causes the linear movement of the dispensing device26. At the same time, the coating plate222spins with the chuck plate224such that the coating material202is coated from a first circle to a second circle without overlap between circles on the coating plate222when the dispensing device26is moved from the first position to the second position by the pulley assembly24.

In one embodiment, the pulley assembly24includes a pulley belt210and two pulley wheels212connected to the pulley belt210. A pair of two rods201go through the two pulley wheels212and is mounted on the cross beam200at one end through the sliding housing211. As shown inFIG. 2B, the vessel204, the vessel holder206and the adaptor208are immobilized on the pulley belt210that move simultaneously with the pulley belt210. The pulley belt210is driven by the two pulley wheels212, which is rotated by the drive gear214that is touched and rotated by the stepper pin216, as shown inFIG. 2C. The utilization of the pulley assembly24is to translate the angular rotation of the drive gear214to linear movement on rails213in radial direction.

In one embodiment, the stepper pin216has a gear218with teeth at different sizes, including 0.5, 1.0, 1.5 and 2.0 mm, as shown inFIGS. 2C and 2E. Differently sized teeth of the gear218allow different degrees of the movements of the dispensing device26on rails213. The gear218of the stepper pin216can be adjusted manually. More sophisticated stepper pin216could be incorporated for continuously variable electronic control of gears or replaced by an electro-mechanical optical rotary encoder to trigger linear stepper movement.

In one embodiment, as shown inFIG. 2F, the dispensing assembly20includes a smooth wheel220that spins with the spinning coating plate222while keeping the dispensing assembly20in the stationary position. The function of the smooth wheel220is to support the weight of the dispensing assembly20and to maintain constant space between the coating plate222and the dispensing assembly20. The smooth wheel220is capable of detecting the surface flatness variation of the coating plate222by touching the edge of the coating plate222, so that the dispensing assembly20can adjust the height relative to the base assembly22through the sliding housing211inside the cross beam200to maintain constant space between the coating plate222and the dispensing assembly20, especially the dispense nozzle234when the surface flatness of substrate is variable.

In one embodiment, as shown inFIG. 2G, the dispensing device26further has a tubing assembly28, including a first tubing226and a second tubing228. The tubing assembly28is mounted to the vessel holder206and inserted to the vessel204. As shown inFIGS. 2G and 2H, the first tubing226includes a check valve230and an air venting valve232. The check valve230provides one-direction flow in the first tubing226. The air venting valve232releases vacuum inside the vessel204and accurately controls the flow of the coating material202. The second tubing228has a dispense nozzle234with bevel tip235for automatic delivery of the coating material202to the coating plate222as shown inFIGS. 2I and 2J. The bevel-tip nozzle234,235, as shown inFIG. 2J, supplies the coating material202only when the coating material202is consumed on the coating plate222. The nozzle234reliably provides even flow to prevent overflow, inconsistent flow, and other irregular flow patterns. The bevel tip235is shaped similar to the spreader slide which spreads the coating material202with a constant angle on the microscope slide. The bevel tip235of the nozzle234is not necessarily in contact with the coating plate222. The contact angle of 10˜45° for the bevel tip235has been tested optimally for spin coating. If the contact angle is greater, the coated film would be thicker, provided that the nozzle size is fixed and other dispense factors are constant.

To allow the coating material202to be dispensed from the first position to the second position, the dispensing device26moves by the rotating pulley assembly24connected to the drive gear214, in which the drive gear214is touched by the stepper pin216that revolves when the chuck plate224spins. Due to the spinning of the chuck plate224, the coating material202is coated in monolayered circles on the coating plate222from the first circle to the second circle when the coating material202is dispensed from the dispensing device26from the first position to the second position.

In one embodiments,FIGS. 3A and 3Billustrates the structure of the base assembly22inside the bottom housing110, including a control board304, an electric motor302, a mounted plate300, spacers308, and rubber cushion feet310. The motor302and the control board304are immobilized on the mounted plate300. The mounted plate300is fixed to the bottom of the bottom housing110by the spacers308. The rubber cushion feet310are fastened to the bottom holes114of the bottom housing110, as shown inFIG. 1F. As shown inFIG. 3E, the chuck plate224is connected to the motor through a shaft306. The control board304is a printed circuit board with electronic components for controlling all elements in the automatic spin coating system10, including motor control and temperature control.

In one embodiment, the chuck plate224is utilized to hold the coating plate222in place by two immobile pins238and one mobile pin236, as shown inFIG. 3D. The coating plate222can be a glass disc or any round substrate, and is for receiving the coating material202. The cooling and heating elements are enclosed in the chuck plate224. The stepper pin216is mounted on the chuck plate224at predetermined radius.

In one embodiment, the method of the automatic spin coating system10comprises rotating the chuck plate224continuously by the motor302, and moving the dispensing device26once every complete revolution from the first position to the second position by the pulley assembly24. The coating material202loaded in the vessel204is discharged from the dispensing device26toward the rotating coating plate222secured on the chuck plate224. The coating parameters are controlled by the control panel106on the top housing100. In one embodiment, the temperature of coating plate222can be accurately controlled to preserve viability and morphology of the coating materials202.

In one embodiment, the moving step of the automatic spin coating system10is accomplished by rotating the drive gear214connected to the pulley assembly24. The drive gear214is rotated by the stepper pin216so as to cause the movement of the dispensing device26. The dispensing device26has one or more sliding housings211inside the adaptor208, which stabilize and smooth the movement of the dispensing device26on rails213.

In one preferred embodiment, the smooth wheel220is rolling and remains stationary on the spinning chuck plate224. The stepper pin216is rotated by the chuck plate224that engages the drive gear214of the dispensing assembly20. The stepper pin216, the drive gear214and the pulley assembly24translate the angular rotation of the coating place222to the linear movement of the dispensing device26on rails213in the radial direction. The stationary rolling step of the smooth wheel220is to maintain the constant space between the coating plate222and the dispensing device26.

Example Result 1

As an example 1, an experiment of the automatic spin coating system10is carried out for making a thin monolayer blood coating. As shown inFIG. 4, fresh peripheral whole blood was spin-coated on a 100 mm-diameter glass disc at spin speed of 60 RPM, bevel-tip contact angle of 10°, tip-substrate space of 0.1 mm, nozzle size of 23 gauge, stepper pin's scale of 0.5 mm, and substrate temperature of 22° C. The blood was directly dispensed from a 4 mL BD Vacutainer K2-EDTA lavender tube with conventional closure. The resulted monolayer blood film had a single layer of dispersed blood cells with intact morphology across the entire glass disc.

Example Result 2

As an example 2, an experiment of the automatic spin coating system10is carried out for making a thick monolayer blood coating. As shown inFIG. 5, approximately 1 mL of peripheral whole blood from a cancer patient has been spin-coated and fully dried on a 100 mm-diameter glass disc at spin speed of 30 RPM, bevel-tip contact angle of 45°, tip-substrate space of 0.3 mm, nozzle size of 23 gauge, stepper pin's scale of 1 mm, and substrate temperature of 37° C. The blood was directly dispensed from a 10 mL CellSave preservative evacuated tube. The thick blood film, as shown inFIG. 5, has been used for identification, enumeration, and examination of rare tumor cells in the peripheral blood.

The above descriptions are those of current embodiments of the invention. Various alterations and changes can be made without departing from the spirit and broader aspects of the invention, which are to be interpreted in accordance with the principles of patent law including the Doctrine of Equivalents.