Porous Silicon Microbioreactors - Applications and Technology

Abstract: Microfluidic systems have become one of the most interesting fields in the research of chemical analysis. Miniaturized systems exhibit numerous practical advantages when compared with traditional batch-scale synthesis such as lower sample volumes, increased control of the reactions and higher sample throughput. This thesis describes the development and applications of a parallel channel microreactor in porous silicon. The microreactor is fabricated by anisotropic etching in <110>-silicon and subsequently made porous by anodising in an HF electrolyte. In various designs the microreactor has been used in different miniaturized analysis systems. Both as an enzyme reactor with immobilised trypsin for protein digestion in a miniaturized sample handling system for protein identification with MALDI-TOF MS, and with immobilised yeast cells in a system for handling and monitoring of cell-released products from living cells. In order to minimise internal mass transport limitations in the microreactor, the porous morphology has been varied, both by altering the overall design of the reactor structure, and by varying the anodisation conditions. This has been done for two different enzymes to illustrate the need to adapt the porous matrix to different substrate molecules. To enhance the external mass transport, the transport of substrate from the main flow to the immobilised walls, acoustic streaming was evaluated as a way to induce vortex flows in the channel. The microreactor sensitivity of fabrication errors and blocking of the channels was investigated by fabricating reactors with different channel width distributions and valuate their performance.