Abstract:
An electrosprayer for insect and arthropod tagging having a nozzle cartridge comprising a liquid reservoir, a high voltage connector, and at least one nozzle; a spray chamber where each nozzle is directed into the spray chamber; and a high voltage power supply, where the power supply applies voltage through the high voltage connector. Also disclosed is the related method for tagging insects and arthropods.

Description:
PRIORITY CLAIM 
       [0001]    The present application is a non-provisional application claiming the benefit of U.S. Provisional Application No. 61/786,770, filed on Mar. 15, 2013 by Horn Bon Lin et al., entitled “ELECTROSPRAYER FOR ARTHROPOD TAGGING,” the entire contents of which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates generally to insect and arthropod tagging and, more specifically, to tagging using an electrosprayer. 
         [0004]    2. Description of the Prior Art 
         [0005]    A reliable method for tagging insects (and other potential appropriate arthropods, such as scorpions, spiders, etc., hereinafter simply referred to as “insects”) is a key component in studies of their biology, ethology, and demography. Reliable and effective methods depend on a device that can consistently deliver the tagging material onto the target insects efficiently. Devices are needed to tag insects with marking agents that include: fluorescent dyes, quantum dots, molecular beacons or aptamers and proteins, and magnetic particles. Moreover, the devices need to tag insects in a short period of time, i.e., within a few seconds to a minute to avoid over-stressing the organism. 
         [0006]    Current insect tagging devices utilize nebulization to create and apply liquid droplets for coating. This method is relatively ineffective because the bodies of insects are typically covered with hairs or bristles (setae) that are dense enough to prevent droplets larger than about 50 microns from reaching the exoskeleton below. In this fashion, the bristles on the insect&#39;s body act as a hydrophobic barrier for protection, shielding the subject from foreign materials such as rain, mist, and small debris. Nebulization methods of droplet creation typically produce droplets too large to penetrate this protective barrier. When using these methods, excessive wetting of the insects usually results from efforts to compensate for the lack of penetration of the droplets. This is not only wasteful of potentially expensive reagent solutions, but can leave such high amounts of fluid on the insects so as to incapacitate and/or harm them, while still failing to provide a satisfactory coating. 
       BRIEF SUMMARY OF THE INVENTION 
       [0007]    The aforementioned problems are overcome in the present invention which provides an electrosprayer for insect and arthropod tagging having a nozzle cartridge comprising a liquid reservoir, a high voltage connector, and at least one nozzle; a spray chamber where each nozzle is directed into the spray chamber; and a high voltage power supply, where the power supply applies voltage through the high voltage connector. Also disclosed is the related method for tagging insects and arthropods. 
         [0008]    The present invention pertains generally to the use of an electrospray, chamber device used for the labeling of arthropods (insects) with specific tagging agents including fluorescence dyes, quantum dots, magnetic metallic particles, molecular proteins, and biological binding materials. The invention relates to an apparatus that is capable of generating charged droplets that are sub-micrometer or even nanometer in size for efficient topical coating (tagging) of insects. The ability to spray-coat (tag) insects in a consistent manner using these materials is useful over a broad spectrum of sciences. Behavior monitoring and forensic studies are two examples of areas that benefit from the tagging of insects. 
         [0009]    The electrospray device of the present invention produces droplets that can range in size from nanometers up to a few micrometers. This size range of droplets more easily penetrates between the body bristles to the exoskeleton underneath. Additionally, the electrospray process places a substantial amount of static charge onto the surface of the droplets. This charge is beneficial since it attracts the droplets to the insect body for better adhesion. Additionally, once the droplets are placed onto the subjects&#39; body beneath the bristles, they are protected from washing or being bumped off; thus creating a more permanent method of tagging. Electrosprays operate at low mass flow rates that will not be mechanically violent to smaller subjects such as gnats, mosquitoes, etc. Flow rates typically are less than 5 μl/min (compared to about 1 ml/min [200 times greater] for typical nebulizers). This has the additional advantage that a quantity of about 5 ml of tagging solution could be continuously sprayed for more than 16 hours. Due to the higher efficiency of the smaller droplets from an electrospray, both the amount of material needed and the exposure time (less than 5 seconds in typical cases) can be considerably reduced. 
         [0010]    These and other features and advantages of the invention, as well as the invention itself, will become better understood by reference to the following detailed description, appended claims, and accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a schematic of an electrospray nozzle cartridge assembly. 
           [0012]      FIG. 2  shows (a) the basic component of an electrospray cartridge and (b) a single nozzle cartridge seen from below. 
           [0013]      FIG. 3  is a schematic of an insect electrospraying device. 
           [0014]      FIG. 4  is a microscope photo of an area on a fly wing after being electrosprayed with rhodamine 6G (orange) dye (left and lower). The image shows individual dye droplets much smaller than the setae and spaces between the setae (individual seta are approx. 100 microns in length). 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0015]    In view of the foregoing, it is therefore an object of the present invention to provide an effective sprayer device particularly useful for efficiently and effectively tagging insect subjects. It is a further object of the invention to provide a spraying apparatus that is capable of generating a charged solution into the chamber to coat insects with low concentrations and quantities of aerosol droplets. The solution comprises tagging agents or a mixture of tagging agents, such as fluorescent dyes, quantum dots, molecular beacons, aptamers, proteins, and aqueously suspended metallic particles. These and other objects of the invention are achieved via a liquid spraying device. The device components include: an electrospray nozzle cartridge, a high voltage power supply, a spraying chamber, and a laser for visually monitoring the electrospray operation. 
       ELECTROSPRAY NOZZLE CARTRIDGE ASSEMBLY 
       [0016]    The nozzle cartridge is shown in  FIG. 1 . In a preferred embodiment, it comprises a 1-inch diameter cylinder made of polypropylene plastic that forms a central liquid reservoir. This central liquid reservoir supplies the (liquid) tagging solution to the electrospray nozzle(s) located at the bottom of the nozzle cartridge. The cartridge holds the electrospray nozzle(s) in place and accommodates an electric connector wire to be attached to the high voltage source for the electrospraying operation. The volume for the reservoir is typically 1-5 ml. The number of electrospray nozzles mounted at the bottom of each cartridge provides control over the rate of application of tagging material. The design shown in  FIG. 1  has been kept simple to reduce fabrication cost. Cartridges with varying number of nozzles and array configurations can be constructed while maintaining the overall dimensions of the piece. This establishes an interchangeable standardized part, permitting easy replacement in case of clogging or desired nozzle re-configurations (e.g., for application rate changes).  FIG. 2  shows two photos showing (a) a vertical view and (b) a bottom-end orientation showing a single electrospray nozzle. 
         [0017]    In a preferred embodiment, the electrospray nozzles are created from a ¾″ length section of silica capillary tubing. The outside diameter (O.D.) of this tubing is 360 micrometers, and can have various inside diameters (I.D.) ranging from 25 to 150 micrometers. To mount an electrospray nozzle, a hole matching the O.D. is bored into the bottom of a cartridge. An electro spray nozzle is inserted into the hole, so that the capillary tubing protrudes slightly above the inside bottom of the reservoir, and is fixed with adhesive applied to the outside surface. The central section of the cartridge will have been counter-bored, or inset, so that the nozzles do not protrude below the end of the cartridge body. This serves to protect the nozzle tips while allowing the cartridge to be placed upright on a flat surface. 
         [0018]    A common syringe connector (e.g. Luer Lock) can be built into the top end of the cartridge so that a syringe can be used to inject liquid solution into the reservoir and to provide a pressure to prime the nozzle(s) at the beginning of operation, just prior to the application of the high voltage (HV) to begin the electrospray. A direct current (DC) HV (typically in the range of 2.5-10 kilovolts) is applied through the embedded HV connector that is tapped into the side-wall of the cartridge. A very fine spray of submicron droplets will result from the nozzle(s) at the bottom of the cartridge when these conditions are met. 
         [0019]    These standardized interchangeable cartridges can be easily inserted into the top section of the Head Assembly as described in the following paragraphs. 
       HEAD ASSEMBLY 
       [0020]    The head assembly comprises a top section and the nozzle cartridge assembly (described above) as shown in  FIG. 3 . In a preferred embodiment, a standardized, commercially available high voltage connector is built into the top section. When the nozzle cartridge is inserted into the top section, the high voltage connector built into the top section makes electrical contact with the customized high voltage connector on the nozzle cartridge to complete the circuit for electrospray operation. 
       SPRAY CHAMBER 
       [0021]    The spray chamber provides a confinement space for tagging the insect subjects. A bottom portion of the head assembly fits into a top portion of the spray chamber. The floor of the spray chamber is an electrically grounded conducting plate required for electrospray operation. In a preferred embodiment, the spray chamber is cylindrical in shape and made of transparent plastic such as Lucite with optical windows built into the sides. Two of these windows should be diametrically opposed to permit the laser beam to propagate through the center of the chamber and illuminate the electrospray plume when in operation. A third window can be used for viewing the laser light scattered by the spray droplets. 
       CHAMBER BODY 
       [0022]      FIG. 3  shows the chamber body as a transparent, cylindrical tube of Lucite. While  FIG. 3  is not to scale, typical dimensions are 2 inches (diameter)×⅛ inches (thickness)×2 inches (height). There are three openings cut to accommodate three optical windows. The diametrically opposed pair of windows is centered top to bottom and is about 1 inch long. A third, viewing window may be placed at an arbitrary angle. 
       BOTTOM PLATE 
       [0023]    The bottom plate comprises a Lucite plate imbedded with a metal grounding plate. The circular metal (aluminum or copper) grounding plate is ¼-inch thick, and serves as an electrical ground for the electrospray. The grounding plate diameter matches the chamber body inside diameter. The upper part of the Lucite bottom plate is bored out to match the metal ground plate diameter. Its function is to isolate the grounding plate from any contact with the surroundings for safety reasons. The grounding plate is accessed for connection to the ground connector through a hole drilled through the side of the Lucite plate. This permits a metal rod to connect the grounding plate to an outside high voltage connector. A standardized commercial high voltage connector of the opposite polarity to the top section is then connected to this metal rod and attached to the bottom plate. 
       HIGH VOLTAGE DC POWER SUPPLY 
       [0024]    A commercial power supply capable of providing up to 10 kilovolts of DC voltage is required. During operation, the current from a typical electrospray has been found to be less than 100 nanoamperes, so a low current power supply is adequate, and recommended for safety considerations. 
       TYPICAL OPERATION 
     Electrospray 
       [0025]    For operating the electrospray, there are several steps to follow. With a filled cartridge in place, connect the high voltage source to the HV connector on the top section. Using the laser to illuminate the area just below the nozzle cartridge gradually dial the voltage up until the spray action is observed. If the voltage has reached the maximum voltage that the power supply can provide and no spray action is observed, turn the voltage down to zero and wait for a minute to allow discharge of any residual voltages. Then place an air-filled syringe onto the syringe adapter on the top of cartridge and push the syringe to squeeze some liquid out of the nozzle tip(s) to ensure a capillary is not clogged. Turn on the voltage and repeat again until the spraying occurs. 
       Insect Spraying 
       [0026]    With the high voltage source turned off and disconnected from the device, pull out the head assembly from the sprayer chamber and drop the insect(s) for tagging through the opening from the top into the chamber. Replace the assembly top. After connecting the HV wire gradually increase the HV power source and watch the spray action through the viewing window until the spray is going steadily as described above. Typical spraying times are a few seconds, but may need to be adjusted depending on the type and number of insects being tagged. After spraying, turn the voltage and the laser off, and wait for at least one minute to allow any residual static charges to dissipate. Pull off the head assembly to retrieve the sprayed insect(s). 
         [0027]    As an illustration of the technique,  FIG. 4  is a microscopic image of a blow fly wing in which the left lower diagonal area has been electro sprayed with a dye. This area shows a nearly uniform coating, compared to the normal uncoated wing area in the upper right. In this particular case, the dye used was an aqueous solution of rhodamine 6G. 
         [0028]    In the description of this invention specific dimensions have been listed. These specific dimensions are not required to produce the desired effect of properly tagging insects. Constraints on the volume of the chamber are only such that the insects are not further than approximately 2 inches from the spray nozzles. The one inch diameter of the spray cartridges has been used in the development due to convenience, since various off-the-shelf supports use this dimension. The specific material the apparatus is created from is not needed to be the same as listed here, but does need to be electrically nonconductive. 
         [0029]    The above descriptions are those of the preferred embodiments of the invention. Various modifications and variations are possible in light of the above teachings without departing from the spirit and broader aspects of the invention. It is therefore to be understood that the claimed invention may be practiced otherwise than as specifically described. Any references to claim elements in the singular, for example, using the articles “a,” “an,” “the,” or “said,” is not to be construed as limiting the element to the singular.