Responsive hydrogel membranes

J. P. Baker and R. A. Siegel, Hysteresis in the glucose permeability versus pH characteristic for a responsive hydrogel membrane, Macromol Rapid Commun., 17,409 15 (1996). 

Membrane structures stimuli-responsive hydrogel membrane (a), membrane with stimuli-responsive grafted brushes (b), stimuli-responsive membrane with porous substrate (c) and responsive gates (d). Source Reproduced from Chu, Xie and Ju (2011). Stimuli-responsive membranes Smart tools for controllable mass-transfer and separation processes. Chinese Journal of Chemical Engineering, 19,891-903. Copyright (2012), with permission from Elsevier.) (Chu eta ., 2011). 

Tokarev I, Gopishetty V, Zhou J, Pita M, Motomov M, Katz E, Minko S. Stimuli-responsive hydrogel membranes coupled with biocatalytic processes. ACS Appl Mater Interfaces 2009 1 532 536. 

Figure 3.15 Illustration of the use of a responsive hydrogel to control the passage of small molecules through a membrane. From reference 1.

The thin hydrogel membranes exhibit a fast response time of 25 sec to 98% equilibrated signal and a fast hydration time of several minutes. The sensor chips can be stored dry for at least one year at 4 °C without changes in performance. 

The same transducers covered with the polyHEMA membranes can serve as a basis for several other amperometric sensors. The optimum trade-off between rapid response (thin membrane) and stirring independency (thicker membranes) should be found for each particular application (77). In many cases, the hydrogel membrane... 

Reactive or catalytic systems are based on pH-responsive hydrogels where the chosen reaction generates a pH shift, which in mm leads to a swelling change in the hydrogel. This response can either be used to increase the internal mesh size to increase solute diffusivity in the gel phase for a diffusive membrane [44] or alternatively the gel can be used as a mechanical valve within the pores of a microporous membrane such that a convective flux may be mmed on or off in response to analyte... 

FIGURE 16.8 Stmcture of a pore-filled membrane. A responsive hydrogel is incorporated into the pores of the substrate membrane to form a stable composite membrane. 

Fig. 27 Cross-sectional view of a bioresponsive insulin delivery system, a feedback-regulated drug delivery system, showing the glucose oxidase-entrapped hydrogel membrane constructed from amine-containing hydrophilic pol5mier. The mechanism of insulin release, in response to the influx of glucose, is also illustrated. (From Ref. l)...

Eddington DT, Beebe DJ (2004b) A valved responsive hydrogel microdispensing device with integrated pressure source. J Microelectoromech Sys 13 586-593 Feil H, Bae Y, Feijen J, Kim S (1991) Molecuar separation by thermosensitive hydrogel membranes. J Membr Sci 64 283-294... 

Huang R, Kostanski LK, Filipe CDM, Ghosh R. Environment-responsive hydrogel-based ultrafiltration membranes for protein bioseparation. Journal of Membrane Science. 2009 336(l-2) 42-49. 

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