Valve chemostat

The principle discussed above has been used to develop an electronically adjustable miao chemostat valve allowing feedback control to keep constant concentration of certain species in solution. " The chemostat consists of silicon-based upper and bottom plates as well as a circuit card for the elertric connection to the PC-controlled power supply. The upper plate carries a platinum temperature sensor and contains a hydrogel chamber ((600 x 600 x SSOjpm ), which is covered by a perforated membrane. The bottom plate has similar con-stmction with an integrated platinrrm heating element (Figure 36(a)). ... 

Figure 36 The principal design of the micro chemostat valve (a) SEM image of the microgel particles used as actuators (b) the flow rate as a function of temperature for different 1-propanol concentrations (c). Reprinted with permission from Richter, A. Turke, A. Rich, A. Adv. Mater. 2007, 19,1109-1112.3 Copyright 2007 Wiley-VCH Verlag GmbH.

Fig. 1. Kubitschek style chemostat. A, Air pump B, hosecock clamps (closed during autoclaving) C, growing culture D, air exit port E, ground glass joints F, syringe filter, G, gang valve H, bottle containing water I, input area K, heating tape M, fresh medium O, siphon P, peristaltic pump R, rubber stopper with holes S, splash shield T, silicone rubber tubing W, waste Y, waste collection tube. Circles in the liquids represent bubbles. Stippling indicates media with cells.

In presence of certain substances, the phase transition temperature of thermo-sensitive hydrogels is altered. This phenomenon is used to design electrothermi-cally adjustable hydrodynamic microtransistors, which are also called chemostat microvalves (Richter et al. 2007a). The valve seat of the device (Fig. 14a) is tempered by a heater and an integrated temperature sensor is used for a closed-loop control. The volume phase transition temperature of PNIPAAm decreases with increasing alcohol content in water (Fig. 14b, solid symbols). Therefore, each critical alcohol concentration or volume phase transition correlates with one characteristic isotherm. Tempered at a particular isotherm the valve switches at a certain concentration (Fig. 14b, open symbols). 

Fig. 6. Chemostat for continuous cultivation of Hydrogenomonas. 1 medium reservoir 2 pump 3 constant-level vessel 4 timer 5 valve 6 thermal trap 7 collecting vessel 8 flow meters 9 Waldhof cylinder...

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