A Nanoliter droplet-based electrochemical sensor integrated with a microfluidic system for detecting dissolved oxygen was fabricated and demonstrated. The fabricated sensor consists of 2 main parts: three ?gold microelectrode which measure oxygen concentration level and PDMS microfluidic channel that is capable of generating a nanoliter scale droplet and encapsulating this droplet in trapping region.
Compared to other dissolved oxygen sensors, the structure of this sensor is simple and reduces experimental process time. Moreover, generating nanoliter droplet reduces the consumption of precious reagent substantially.
Deteceting oxygen level in the electrolyte (0.1M KCl) was performend through two step. Once the 0.1M KCl solution was flowed into the continuous phase of the microfluidic sensor chip, the droplet was generated and captured at the trapping region (450um), resulting in producing -0.875uA reduction currents at the full oxygen state. After that, 0.5M Na2SO3 solution as dispersed phase was injected into the microfluidic sensor chip and 0.1M KCl droplet was surrounded 0.5M Na2SO3 droplet to detect oxygen level in 0.1M KCl solution. The measured reduction current showed -0.458uA at the zero oxygen state. The repeatability test of the proposed sensor was also carried out by removing 0.5M Na2SO3 solution in the channle and represented -0.875uA. Finally, the sensor was successfully proved as the electrochemical dissolved oxygen sensor. The result shows that this Naoliter Droplet Based Microfluidic Electrochemical Dissolved Oxygen Sensor has a very promising potential to be improvised and applied as detection tools in various medical fields, particularly when only nanoliter volume of reagent is available or should be used for various reasons. The total dimension of the microfluidic biosensor chip is only 58 mm x 78 mm making it suitable for point-of-care design and consideration.