Chemical apparatus and process disinfecting – deodorizing – preser – Control element responsive to a sensed operating condition
Reexamination Certificate
1998-12-10
2001-10-02
Warden, Jill (Department: 1743)
Chemical apparatus and process disinfecting, deodorizing, preser
Control element responsive to a sensed operating condition
C436S180000, C073S863320, C073S864020, C347S068000, C347S071000, C310S326000, C310S328000
Reexamination Certificate
active
06296811
ABSTRACT:
TECHNICAL FIELD
The invention pertains to the controlled dispensing of small volumes of fluid. The invention has particularly advantageous application to automated and integrated systems and methods for rapidly identifying chemicals with biological activity in liquid samples, particularly automated screening of low volume samples for new medicines, agrochemicals, or cosmetics
INTRODUCTION
The dispensing of small volumes of fluids is an important aspect of several different technologies, from various printing techniques to chemical screening apparatus for drug discovery. Thus, systems and methods for controllably and accurately dispensing liquid, especially small liquid samples, can benefit a number of different fields. The agrochemical, pharmaceutical, and cosmetic fields all have applications where large numbers of liquid samples containing chemicals are processed. In some instances, the processing of liquid samples, such as in pharmaceutical arts, which usually demands complicated liquid processing for drug discovery, can obtain throughput rates of approximately 10,000 samples per day or greater.
A wide variety of designs for dispensers have been utilized. In some applications, a piezoelectric actuator is coupled to a fluid chamber that contains a nozzle for droplet ejection. When the piezoelectric material is actuated, a droplet of fluid is ejected through the nozzle. Such a system is illustrated in U.S. Pat. No. 4,877,745 to Hayes, et al., which is incorporated herein by reference in its entirety.
This method of droplet ejection includes several complications, however, such as the production of undesired fluid responses to actuation which interfere with efficient droplet ejection. One possible method of damping undesired fluid responses in a piezoelectrically compressed fluid chamber involves placing selected materials inside or around the rearward portion of the fluid chamber that cushion or passively dampen the pressure wave in the chamber. Some of these techniques are described, for example, in U.S. Pat. No. 3,832,579 to Arndt, U.S. Pat. No. 4,233,610 to Fischbeck et al., and U.S. Pat. No. 4,528,579 to Brescia. However, these passive systems are relatively expensive to implement, and may need significant alteration depending on the physical properties of the fluid being dispensed.
Another proposed solution to undesired fluid responses, illustrated in U.S. Pat. No. 4,418,354 to Perduijn (which is hereby incorporated into the present disclosure by reference), involves placing a fluid flow restriction in a portion of the fluid chamber rearward from the nozzle. A dispensing apparatus with a similar functional constriction is commercially available from Packard Instrument Company of Meridan, Conn. as an accessory to the MultiProbe 104. The presence of the restriction, however, produces additional difficulties, such as inhibiting removal of particulate matter that may become inadvertently introduced into the fluid chamber. Once a particle gets inside the fluid chamber, it may become trapped between the small diameter nozzle and small diameter restriction, thereby clogging the device and interfering with the proper operation of the dispenser.
A need therefore exists for efficient droplet dispensing devices which do not suffer from the above mentioned drawbacks.
SUMMARY OF THE INVENTION
The invention is directed to method and apparatus for fluid dispensing. In one embodiment a fluid dispensing apparatus includes a fluid chamber having an opening for droplet dispensing, a first actuator mechanically coupled to and configured to alter the volume of the fluid chamber, and a second actuator mechanically coupled to and configured to alter the volume the fluid chamber. The apparatus may also include a driver connected to actuate the first and second actuators so as to alter the volume of the fluid chamber, whereby a fluid response produced by the first actuator is damped by the second actuator. The actuators may comprise piezoelectric actuators which are actuated substantially simultaneously or sequentially.
Methods of droplet dispensing may comprise altering the volume of a fluid chamber with a first actuator and damping a fluid response to the volume alteration with a second actuator. In one specific embodiment, the altering comprises electrically actuating a first piece of piezoelectric material, and wherein the damping comprises electrically actuating a second piece of piezoelectric material.
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Aurora Biosciences Corporation
Bex Kathryn
Knobbe Martens & Olson Bear LLP.
Warden Jill
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