Integrated Electrochemical Analysis System with Microfluidic and Sensing Functions

An integrated device that carries out the timely transport of solutions and conducts electroanalysis was constructed. The transport of solutions was based on capillary action in overall hydrophilic flow channels and control by valves that operate on the basis of electrowetting. Electrochemical sensors including glucose, lactate, glutamic oxaloacetic transaminase (GOT), glutamic pyruvic transaminase (GPT), pH, ammonia, urea, and creatinine were integrated. An air gap structure was used for the ammonia, urea, and creatinine sensors to realize a rapid response. To enhance the transport of ammonia that existed or was produced by the enzymatic reactions, the pH of the solution was elevated by mixing it with a NaOH solution using a valve based on electrowetting. The sensors for GOT and GPT used a freeze-dried substrate matrix to realize rapid mixing. The sample solution was transported to required sensing sites at desired times. The integrated sensors showed distinct responses when a sample solution reached the respective sensing sites. Linear relationships were observed between the output signals and the concentration or the logarithm of the concentration of the analytes. An interferent, L-ascorbic acid, could be eliminated electrochemically in the sample injection port.