biology

Media dispenser

Media dispenser is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Media dispenser rather than just read about it. In short: 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 contaminat…

Key takeaways

Media dispenser belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Media dispenser to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Media dispenser from memory before moving on to harder problems.

Reference excerpt

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. 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.

List of media dispensers

Floating Piston 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.

Inductive pump

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.

Bottle top 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.

Solid Media Dispenser 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.

Syringe pump

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:

Low Pressure (290N): This syringe pump suitable for high precise dosage of small volumes (nanolitres). Mid Pressure (1000N): This syringe pumps are made for the precise injection of fluids into systems under higher pressures (200 bar) High Pressure (2600N): This work the same as mid pressure bar, but dosing technology pressure can be ranges up to 510 bar. Ultra High Pressure (7000N): This Ultra high pressure is suitable for extreme conditions in terms of high pressures (up to 13,000 psi)

Peristaltic pump

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.

Pipette

… excerpt ends here. Continue reading the full article.

Illustrations

Media dispenser: A peristaltic pump — A peristaltic pump

Worked examples

Example 1 — a first encounter with Media dispenser

Start with the simplest possible case. Write down what Media dispenser claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Media dispenser before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Media dispenser ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Media dispenser

In research: Media dispenser appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Media dispenser in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Media dispenser is common in secondary-school and first-year university syllabi. It links to neighbouring topics Dispensers, Microbiology equipment, so understanding it makes those chapters shorter.
In everyday life: Look for Media dispenser outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Media dispenser in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Media dispenser means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Media dispenser out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Media dispenser in simple terms?

Why does Media dispenser matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Media dispenser?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Media dispenser.