Slow-release is a strategy in material science in which a chemical compound

Chemical compound

A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...

 is introduced into a system at a reduced speed. Slow-release is applied in fertilizer

Fertilizer

Fertilizer is any organic or inorganic material of natural or synthetic origin that is added to a soil to supply one or more plant nutrients essential to the growth of plants. A recent assessment found that about 40 to 60% of crop yields are attributable to commercial fertilizer use...

s, pesticide

Pesticide

Pesticides are substances or mixture of substances intended for preventing, destroying, repelling or mitigating any pest.A pesticide may be a chemical unicycle, biological agent , antimicrobial, disinfectant or device used against any pest...

s and drugs

Medication

A pharmaceutical drug, also referred to as medicine, medication or medicament, can be loosely defined as any chemical substance intended for use in the medical diagnosis, cure, treatment, or prevention of disease.- Classification :...

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Getting a chemical at a certain spot whether it is on a plant or inside the human body comes at a cost because of the spraying effort and pill consumption. If the desired effect is to last, administering the chemical has to be repeated over and over again. Supplying a large single dose reduces that frequency but is not always an option because the large dose is toxic or has adverse side effects compared to a small dose. Slow-release combines the beneficial effects of applying a single large dose distributed over a long time in small quantities. Slow release systems work by reducing the diffusion

Diffusion

Molecular diffusion, often called simply diffusion, is the thermal motion of all particles at temperatures above absolute zero. The rate of this movement is a function of temperature, viscosity of the fluid and the size of the particles...

 of a chemical into the system. The practical technology behind slow-release can be found in Micro-encapsulation

Micro-encapsulation

Micro-encapsulation is a process in which tiny particles or droplets are surrounded by a coating to give small capsules many useful properties. In a relatively simplistic form, a microcapsule is a small sphere with a uniform wall around it...

 or inclusion compound

Inclusion compound

In host-guest chemistry an inclusion compound is a complex in which one chemical compound forms a cavity in which molecules of a second "guest" compound are located. The definition of inclusion compounds is very broad, extending to channels formed between molecules in a crystal lattice in which...

s.

Slow release tablet systems are presently used to maintain steady levels of drugs in the blood.