Schematic of pulsating drug delivery device

The rate at which a solid substance dissolves in its own solution is proportional to the difference between the concentration of that solution and the concentration of the saturated solution. 

Early studies in this field of research formulated two main models for the interpretation of the dissolution mechanism the diffusion layer model and the 

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Figure 4.17 Schematic of pulsating drug delivery device based on feedback inhibition of glucose transport to glucose oxidase through a hydrogel membrane. Changes in permeability to glucose are accompanied by modulation of drug permeability. Reprinted from [97] with permission from American Institute of Physics.

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