Dispensing apparatus having improved dynamic range

Abstract

A method and apparatus for dispensing precise quantities of reagents is disclosed including a positive displacement syringe pump in series with a dispenser, such as an aerosol dispenser or solenoid valve dispenser. The pump is controlled by a stepper motor or the like to provide an incremental quantity or continuous flow of reagent to the dispenser. The pump and dispenser are operated in cooperation with one another such that the quantity and / or flow rate of liquid dispensed by the dispenser can be precisely metered substantially independently of the particular operating parameters of said dispenser to attain a desired flow rate, droplet size or mist quality, droplet frequency and / or droplet velocity.

Description

BACKGROUND OF THE INVENTION1. Field of the InventionThe present invention relates generally to an improved method and apparatus for dispensing chemical reagents and other liquids onto a substrate and, in particular, to various methods and apparati particularly adapted for dispensing precise quantities of chemical reagents onto a receptive membrane, such as to form a diagnostic test strip, having improved dynamic range of operation.2. Description of the Prior ArtClinical 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...

AI Technical Summary

Benefits of technology

The reagent dispensing method and apparatus in accordance with the present invention can dispense desired quantities of chemical reagents or other liquids onto a substrate, such as a receptive membrane, while advantageously providing the ability to independently and precisely adjust droplet size or mist quality, droplet velocity and reagent flow rates, both in terms of per unit time or per unit distance. Thus, the present invention provides new devices and methods of dispensing precise quantities of liquids having improved performance and dynamic range of operation.

In accordance with another preferred embodiment the present invention comprises a method or apparatus for dispensing a reagent onto a substrate. A positive displacement syringe pump is provided in series with a reagent dispenser. The pump is controlled via a stepper motor or the like to provide precision incremental or continuous flow of reagent to the dispenser. The dispenser is selectively operated to form droplets or a mist of droplets of a predetermined droplet size and / or quality which are then deposited onto the target substrate. Advantageously, the droplet size, mist quality, droplet velocity and / or flow rate of the reagent can be precisely controlled independently of the particular system operating parameters of the dispenser.

In accordance with another preferred embodiment the present invention comprises an apparatus for dispensing a liquid onto a substrate, comprising a dispenser having an inlet and an outlet and a valve adapted to be opened and closed at a predetermined frequency and duty cycle to form droplets which are deposited onto the substrate. A positive displacement pump, such as a stepper-motor-operated syringe pump, is hydraulically arranged in series with the inlet of the dispenser for metering predetermined quantities of liquid to the dispenser. The pump and dispenser are operated in cooperation with one another such that the quantity and / or flow rate of liquid dispensed by the dispenser can be precisely metered substantially independently of the particular operating parameters of said dispenser. In this manner, the size, frequency, and velocity of droplets dispensed by said dispenser can each be adjusted substantially independently of the quantity and / or flow rate of liquid being dispensed.

Problems solved by technology

Application of one or more reagents to a test strip substrate is a highly difficult task.

It is often difficult, however, to form sharp lines or other geometric shapes having uniform concentrations of reagent.

Currently available dispensing methods, however, are limited in the flexibility they have to independently adjust and regulate the output of the dispenser in terms of droplet size or mist quality, droplet velocity and flow rates of dispensed reagent.

This can cause undesirable lot to lot variances of reagent coating concentrations or coating patterns.

Often, however, a desired droplet size or mist quality is simply not attainable for a desired production flow rate.

This can increases the cost of production significantly.

Certain dispensers, such as solenoid valves, are also susceptible to clogging by small air or gas bubbles forming in the valve itself or in the lines or conduits which supply reagent or other liquids to the dispenser.

This is a major reliability problem with many conventional solenoid valve dispensers.

While some of these problems can be controlled or mitigated by adding surfactants or various other chemical additives to modify the surface tension or other flow characteristics of the droplets, compatible chemistry is not available for all reagents.

Also the use of surfactants and other chemicals can often lead to other problems either in the test strip itself or in the dispensing apparatus or production processes.

Images