Chemical apparatus and process disinfecting – deodorizing – preser – Control element responsive to a sensed operating condition
Reexamination Certificate
1999-01-28
2003-03-25
Warden, Jill (Department: 1743)
Chemical apparatus and process disinfecting, deodorizing, preser
Control element responsive to a sensed operating condition
C422S105000, C222S504000, C222S559000, C251S129170, C251S129180, C073S863320, C073S864000, C073S864130, C073S864160, C073S864140
Reexamination Certificate
active
06537505
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to an improved valve apparatus for dispensing chemical reagents and other liquids and, specifically, to a reagent dispensing valve that is particularly adapted for dispensing precise microfluidic quantities of chemical reagents.
2. Background of the Related Art
Clinical testing of various bodily fluids conducted by medical personnel are well established tools for medical diagnosis and treatment of various diseases and medical conditions. Such tests have become increasingly sophisticated, as medical advancements have led to many new ways of diagnosing and treating diseases.
The routine use of clinical testing for early screening and diagnosis of diseases or medical conditions has given rise to a heightened interest in simplified procedures for such clinical testing that do not require a high degree of skill or which persons may conduct on themselves for the purpose of acquiring information on a physiological relevant condition. Such tests may be carried out with or without consultation with a health care professional. Contemporary procedures of this type include blood glucose tests, ovulation tests, blood cholesterol tests and tests for the presence of human chorionic gonadotropin in urine, the basis of modem home pregnancy tests.
One of the most frequently used devices in clinical chemistry is the test strip or dip stick. These devices are characterized by their low cost and simplicity of use. Essentially, the test strip is placed in contact with a sample of the body fluid to be tested. Various reagents incorporated on the test strip react with one or more analytes present in the sample to provide a detectable signal.
Most test strips are chromogenic whereby a predetermined soluble constituent of the sample interacts with a particular reagent either to form a uniquely colored compound, as a qualitative indication of the presence or absence of the constituent, or to form a colored compound of variable color intensity, as a quantitative indication of the amount of the constituent present. These signals may be measured or detected either visually or via a specially calibrated machine.
For example, test strips for determining the presence or concentration of leukocyte cells, esterase or protease in a urine sample utilize chromogenetic esters which produce an alcohol product as a result of hydrolysis by esterase or protease. The intact chromogenetic ester has a color different from the alcohol hydrolysis product. The color change generated by hydrolysis of the chromogenetic ester, therefore provides a method of detecting the presence or concentration of esterase or protease, which in turn, is correlated to the presence or concentration of leukocyte cells. The degree and intensity of the color transition is proportional to the amount of leukocyte esterase or HLE detected in the urine. See U.S. Pat. No. 5,464,739.
The emergence and acceptance of such diagnostic test strips as a component of clinical testing and health care in general has led to the development of a number of quality diagnostic test strip products. Moreover, the range and availability of such products is likely to increase substantially in the future.
Because test strips are used to provide both quantitative and qualitative measurements, it is extremely important to provide uniformity in distribution of the reagents on the test strip substrate. The chemistry is often quite sensitive and medical practice requires that the testing system be extremely accurate. When automated systems are used, it is particularly important to ensure that the test strips are reliable and that the measurements taken are quantitatively accurate.
Application of one or more reagents to a test strip substrate is a highly difficult task. The viscosities and other flow properties of the reagents, their reactiveness with the substrate or other reagents vary from reagent to reagent, and even from lot to lot of the same reagent. It is also sometimes necessary or desirable to provide precise patterns of reagent on the test strip having predetermined reagent concentrations. For example, some test strips provide multiple test areas that are serially arranged so that multiple tests may be performed using a single test strip. U.S. Pat. No. 5,183,742, for instance, discloses a test strip having multiple side-by-side detection regions or zones for simultaneously performing various tests upon a sample of body fluid. Such a test strip may be used to determine, for example, levels of glucose, protein, and the pH of a single blood sample.
Typically, a micro-droplet dispensing apparatus is utilized in the preparation and/or analysis of test strips. Of course, micro-droplet dispensing is not limited in application to test strip fabrication and analysis, but it also has a wide variety of other research and non-research related applications in the biodiagnostics, pharmaceutical, agrochemical and material sciences markets. For example, dispensing technology is used in genomic research and analysis, drug screening, live cell dispensing and ink jet printing among others.
Moreover, in addition to dispensing, some applications may also involve aspiration of a chemical reagent or other liquid, wherein a quantity of fluid is aspirated (“sucked”) from a source and then dispensed (“spat”) into or onto a target for further testing and/or processing. For example, a typical application would include a source composed of a 96-microwell plate with a transfer of reagent to a glass slide, microwell plate or membrane.
For several years the industry has been developing dispensing methods based on the use of solenoid valve dispensers. Solenoid valve dispensers generally comprise a small solenoid activated valve which can be opened and closed electronically at high speeds. Solenoid valves of this type are commercially available from sources such as The Lee Company of Westbrook, Conn. The solenoid valve is typically connected to a pressurized vessel or reservoir containing the fluid to be dispensed. In operation, the solenoid is energized by a pulse of electrical current, which opens the valve for a pre-determined duty-cycle or open time. This allows a small volume of liquid to be forced through the nozzle forming a droplet which is then ejected from the valve onto the target. The size and frequency of the droplets and the amount of reagent flow onto the target is typically controlled by adjusting the frequency and pulse-width of energizing current provided to the solenoid valve and/or by adjusting the pressure of the reservoir.
There are several major limitations associated with using a conventional solenoid valve, such as the Lee valve, as a drop-on-demand valve in a reagent dispensing system. The Lee valve generally comprises a solenoid actuator element and a valve element with these two elements being integrated to form a unitary component. The various components of the valve element present a tortuous path for the fluid to flow through. Such a tortuous fluid path results in significant disadvantages, such as localized pressure drops which undesirably lead to bubble precipitation of air or gas in solution. The entrapment of these bubbles in the fluid path can not only degrade the quality of the reagent or liquid dispensed but can also render the dispenser susceptible to clogging. Thus conventional dispensing valves require frequent purges of the fluid into a waste receptacle, thereby, disadvantageously, reducing process efficiency and increasing wasteful consumption of reagent. Moreover, the air or gas bubbles affect the compressibility of the fluid which can complicate the operational dynamics of the dispense and aspirate/dispense functions.
While some of these bubble generation problems can be controlled or mitigated by adding surfactants or various other chemical additives to modify the surface tension and/or other fluid and flow characteristics of the reagent, compatible chemistry is not available for all reagents. Also the use of surfactants and other chemicals can often lead to oth
LaBudde Edward V.
Wilson Anthony D.
BIO DOT, Inc.
Gordon Brian R.
Knobbbe, Martens, Olson & Bear LLP
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