A media dispenser or a culture media dispenser is a device for repeatedly delivering small fixed volumes (typically between 1 ml and 50 ml) of liquid such as a laboratory growth medium like molten agar or caustic or volatile solvents like toluene into a series of receptacles (Petri dishes, test tubes, Fernbach flasks, etc.). It is often important that such dispensers operate without biological or chemical contamination, and so must be internally sealed from the environment and designed for easy cleaning and sterilization before use. At a minimum, a media dispenser consists of some kind of pump connected to a length of discharge tubing or a spout. Dispensers used in laboratories are also frequently connected to microcontrollers to regulate the speed and volume of the medium as it leaves the pump.
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Laboratory media dispensers may include the following, among others: floating piston designs, syringe pumps, peristaltic pumps, pipettes or pipettors, and pressure injection cells. Rotodynamic pumps are generally unsuitable for dispensing laboratory media.
The floating piston type includes electrically and manually operated subtypes. Both include a check valve at either end of the device to ensure the flow of fluids in only one direction.
The electrical floating piston type of media dispenser is based on the principle of an inductive pump. This design uses a floating piston housed inside of a cylinder (typically high-grade ferromagnetic stainless steel) and vibrated according to a magnetic pulse generated by a copper coil inside the cylinder and surrounding the piston. Oscillation of the piston back and forth in the cylinder causes aspiration of fluid into the cylinder at one end followed by ejection from the other end.[1]
A bottle top media dispensers is an inexpensive alternative to the motor-driven inductive pump. This type involves a piston on a plunger which is pushed down against a spring: as the spring pushes the piston back into its original position, it draws the medium up from a reservoir underneath. When pushed down again, plunger infuses the medium out the dispenser tip. Like the electrical model mentioned above, the bottle top dispenser has no gaskets or seals. Unlike the previous model, this one requires no electricity. However, it is limited in the total amount of medium it can dispense before the source bottle requires a refill, making it convenient for small applications but less so for larger. They are also more difficult to calibrate than the pipettes.[2]
A dispenser that is capable of dispensing solids such as powders, resins, microbeads, beads etc. It uses a metal plate containing holes to hold a specific amount of solid material to be dispensed. After the holes are filled with 'powder', a slider is pulled that opens the holes also called the 'dropdown method', letting the powder drop into a tube, well or microtiterplate. As this device is very accurate, it is widely used in laboratories and in the pharmaceutical industry.
A syringe pump consists of one or more syringes which have been pre-filled and loaded into a mechanized device containing a motor-driven lead screw which will push the reciprocating plunger of the syringe(s) for specified distances at specified intervals. These devices are capable of extremely high accuracy and are pulse-free (i.e., the fluid is dispensed in a continuous stream rather than with the pulsations of the peristaltic or inductive pumps) but are limited in volume to the total volume of the attached syringe(s), and, once the emptied, the syringe(s) will require refilling before being used again making them of even more limited use than the bottle top dispensers. They are also among the most expensive types of media dispensers currently on the market. Common syringe pump media are acids, chemicals, coolants, combustible fluids, corrosive agents, gasoline or diesel fuel, non-liquid gas or air, ground water, hazardous materials, high viscosity fluids, liquid metal, oils, potable water, salt water, adhesives, and high temperature media.
Types of pressure syringe pump can vary depending on the company:
Despite their drawbacks, peristaltic pumps have so far been the industry standard for dispensing large volumes of laboratory media: they are capable of dispensing fluid continuously from a reservoir into any number of receptacles, can be used for coarse, thick, or gritty fluids as well as free-flowing thin ones, and unlike many of the other dispenser types, the only contact the pumped fluid has during delivery is with the tubing in which it is being transported: there is never any contact with an internal piston, plunger, or diaphragm, which ensures the highest degrees of sterility and precludes virtually any chemical cross contamination. However, their functionality is limited to the flexible lifetime of this tubing which must be able to withstand hundreds of thousands of compressions without losing integrity; their fluid delivery is pulsed; variation in the flexibility of the tubing means they are among the least precise forms of dispenser; the tubing in a peristaltic pump may rupture unexpectedly— many pumps include shielding to help contain the ruptured fluids, but a rupture can ruin a carefully timed lab procedure and/ or damage the inner workings of the pump itself; few other pump types are more dependent on a microprocessor or more useless in the event of mechanical failure; they along with syringe pumps constitute the most expensive dispensers on the market.[4]
A pipette consists of a long thin tubular tip connected to a hollow cylinder containing a plunger. Pipettes are the simplest, smallest, and in their basic forms, the least expensive type of media dispenser, and are also pulse-free. However, they can only effectively transport one or two fills at a time, and, unless filled from the rear, the tube tip must constantly be reinserted into the source vessel in order to be refilled which creates a repeated opportunity for contamination. They also require the user to do more work than any other type of dispenser both in terms of time to fill a receptacle and energy necessary to make sure each fill is precise and accurate (digital pipette models may work faster and require less work per fill from the user than manual ones, though these are then subject to the availability of electricity and the possibility of mechanical failure). On the plus side, the simple pipette has few moving parts, rarely or never breaks down, and is capable of moving thick or thin media including those containing abrasives with relative ease.
A pressure injection cell dispenser is capable of administering only the very smallest amounts of extremely pure non-viscous media, though it does so with the absolutely highest degree of precision. The cells in this dispenser, which are usually between 0.5 ml and 2 ml in capacity, must be individually filled using a centrifuge before being inserted into the dispenser. Once loaded, the amount of fluid dispensed will depend on the pressure of an inert gas such as helium or nitrogen released from a tank and pushed against the cells at pressures of up to 8,500 pounds per square inch (59 MPa). The pressure injection cell is considered a 'dynamic' pump type rather than a 'displacement' type because it achieves movement of liquids by exerting force on them directly with no moving parts.
Agar (pronounced , sometimes ) or agar-agar is a jelly-like substance, obtained from red algae.Agar is a mixture of two components: the linear polysaccharide agarose, and a heterogeneous mixture of smaller molecules called agaropectin. It forms the supporting structure in the cell walls of certain species of algae, and is released on boiling. These algae are known as agarophytes, and belong to the Rhodophyta (red algae) phylum.Agar has been used as an ingredient in desserts throughout Asia, and also as a solid substrate to contain culture media for microbiological work. Agar can be used as a laxative, an appetite suppressant, a vegetarian substitute for gelatin, a thickener for soups, in fruit preserves, ice cream, and other desserts, as a clarifying agent in brewing, and for sizing paper and fabrics.The gelling agent in agar is an unbranched polysaccharide obtained from the cell walls of some species of red algae, primarily from tengusa (Gelidiaceae) and ogonori (Gracilaria). For commercial purposes, it is derived primarily from ogonori. In chemical terms, agar is a polymer made up of subunits of the sugar galactose.
Diebold 10xxThe Diebold 10xx (or Modular Delivery System, MDS) series is a third and fourth generation family of automated teller machines manufactured by Diebold.
Growth mediumA growth medium or culture medium is a solid, liquid or semi-solid designed to support the growth of microorganisms or cells, or small plants like the moss Physcomitrella patens.
Different types of media are used for growing different types of cells.The two major types of growth media are those used for cell culture, which use specific cell types derived from plants or animals, and microbiological culture, which are used for growing microorganisms, such as bacteria or fungi. The most common growth media for microorganisms are nutrient broths and agar plates; specialized media are sometimes required for microorganism and cell culture growth. Some organisms, termed fastidious organisms, require specialized environments due to complex nutritional requirements. Viruses, for example, are obligate intracellular parasites and require a growth medium containing living cells.
PipetteA pipette (sometimes spelled pipet) is a laboratory tool commonly used in chemistry, biology and medicine to transport a measured volume of liquid, often as a media dispenser. Pipettes come in several designs for various purposes with differing levels of accuracy and precision, from single piece glass pipettes to more complex adjustable or electronic pipettes. Many pipette types work by creating a partial vacuum above the liquid-holding chamber and selectively releasing this vacuum to draw up and dispense liquid. Measurement accuracy varies greatly depending on the style.
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Key Characteristics
In a busy laboratory, preparing and dispensing plated media or broths in tubes and bottles can be a time consuming process particularly when large sample numbers need to be processed.
Although reducing labour costs can provide a significant reason to implement an automated media preparation process, there are additional factors that need to be included: the cost of storage space and facilities if ready-to-use [RTU] media are considered [plus of course the purchase price]; manual media preparation can suffer from contamination problems.
An in-house automated media preparation system can also provide a virtual on-demand supply of media for those occassions when changes in normal laboratory workflow occur.
At the most basic level, automation of media preparation might involve the reproducible transfer of liquid agar or broth to plates and tubes or bottles. There are semi-automated filling sytems that can achieve this for the smaller laboratory.
When large numbers of plates, tubes, vials, bottles etc. need to be produced then the whole process can be fully automated.
There are now high capacity fully automated media sterilisers and plate pourers, fillers and dispensers. Just put in dehydrated media; select the correct process procedure and wait for the pre-poured plates or tubes etc. to be produced. Or rather, you can go off and do something else as such systems are truly walk-away.
These fully automated systems are microprocessor controlled and can allow full control over the process parameters such as: sterlization temperature and time; pouring temperature etc.. Some systems are able to add thermolabile materials such as blood or selective agents at particular points in the process.
With some systems the whole operation can be monitored by computer - providing complete traceability for each batch: and plates etc. can be automatically bar coded with the relevent batch or lot number etc.
Not all laboratories require complete automation of the media preparation process. Almost all microbiology laboratories will have access to or already have an autoclave or sterilizer, if that is in place then all that many laboratories would require is an automatic dish stacker/pourer or a bottle/vial dispenser. In common with fully automated systems some of these can offer optional printers for plate identification etc. Other features might include accessories that can pour bi-plates.
There are occassions when non-standard plate design or completely different formats such as microtitre plates might need to be filled with agar, broths or other liquid. The solution for these applications can usually be solved with a robotic system which again can offer true 'walk away' operation. Depending upon the accessories and the sample/assay in question available these can even automate the complete sample assay. This type of sytem is commonly found in clinical applications and is usually an integrated sample assay instrument and not referred to as a robot.
How to Choose a Media Preparator/Filler for Your Microbiology Lab - find out what questions to ask a vendor.
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