A surface-tension-driven fluidic network for precise enzyme batch-dispensing and glucose detection

This paper reports a novel fluidic network dispensing equal amount of enzymes to arrays in parallel for the application of glucose sensing. This network was fabricated by polymer-MEMS technology employing SU-8 resist as enzyme deposition channels and PDMS as blood flow channels. To provide hydrophilic surface property for enzyme batch immobilization, the top-opened SU-8 channel surfaces was treated with O₂ plasma so that the liquids could be successfully driven into each channel automatically by surface tension without external power sources. The liquid filling and withdrawing processes had been successfully accomplished in less than 5 s and demonstrated uniform liquid deposition in each enzyme channel from fluorescence image. Enzyme-based glucose sensing was employed as a model in this fluidic network to test the feasibility for sensor/fluidic network integration. Two different sensor designs, with platinum sensing area of 0.2 and 0.57 mm², respectively, were fabricated in the fluidic network and tested by glucose with concentrations from 8 to 40 mM. The results demonstrated the sensitivity of 18.58 nA/mM for the large sensor and 5.42 nA/mM for the small sensor, and the responses were linearly related to the glucose concentrations. The higher sensitivity of the large sensor resulted from the higher sensing area for enzyme reaction and current collection. The sensitivity was roughly 3.43 times higher for the large sensor with sensing area 2.85 times larger than those for the small sensor. The repeatability of different sensors on the same chips had been characterized to be within 10%. This novel fluidic network has the potential for fast blood sensing in clinical or domestic applications. © 2003 Elsevier B.V. All rights reserved.