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In order to provide the driving force for the collection and transport of the micro liquid in a microfluidic chip developed by our research group in earlier research,this paper presents a micro positive pressure generator based on the released gas by thermal decomposition of azobisisobutyronitrile(AIBN).The AIBN is fixed to a micro-heater and heated to 70 ℃ to produce a certain amount of positive pressure.Experimental measurements show that this micro positive pressure generator can obtain 182 kPa pressure with heating 8.7 mg of AIBN by a heating current of 900 mA.The designed micro positive pressure generator is a smaller size,pressure controllable and easy to produce,and obtained pressure can satisfy the requirements of transdermal interstitial fluid(ISF) extraction.

A microfluidic based Interstitial Fluid(ISF) transdermal extraction tool made from polydimethylsiloxane(PDMS) was designed to the application of continuous glucose monitoring.Four layers of PDMS fabricated by replica molding process were bonded together using oxygen plasma to construct the device,including a Venturi tube for vacuum generation,chambers for the introduction of ISF and normal saline solution,pneumatic valves for fluid control,and interconnected microchannels.Then,the output vacuum of Venturi tube and the close pressure of pneumatic valve were measured.Finally,the ISF extraction and collection function was tested.Results show that the vacuum pressure is used for fluid manipulation and a 92 kPa(absolute pressure) vacuum is achieved,when 220 kPa(absolute pressure) external pressure is applied to the Venturi tube.Moreover,the normally open pneumatic valves can be closed under the operating pressure less than 65 kPa(relative pressure).Under the control of pneumatic valves,the normal saline injection,ISF extraction and collection function of the tool are implemented by using the vacuum generated from the Venturi tube.