A Primer on Microfluidics: From Basic Principles to Microfabrication.

Microfluidic systems enable manipulating fluids in different functional units which are integrated on a microchip. This chapter describes the basics of microfluidics, where physical effects have a different impact compared to macroscopic systems. Furthermore, an overwiew is given on the microfabrication of these systems. The focus lies on clean-room fabrication methods based on photolithography and soft lithography. Finally, an outlook on advanced maskless micro- and nanofabrication methods is given. Special attention is paid to laser structuring processes.

Microfluidic Systems for Antimicrobial Susceptibility Testing.

Human health is threatened by the spread of antimicrobial resistance and resulting infections. One reason for the resistance spread is the treatment with inappropriate and ineffective antibiotics because standard antimicrobial susceptibility testing methods are time-consuming and laborious. To reduce the antimicrobial susceptibility detection time, minimize treatments with empirical broad-spectrum antibiotics, and thereby combat the further spread of antimicrobial resistance, faster and point-of-care methods are needed. This requires many different research approaches. Microfluidic systems for antimicrobial susceptibility testing offer the possibility to reduce the detection time, as small sample and reagent volumes can be used and the detection of single cells is possible. In some cases, the aim is to use human samples without pretreatment or pre-cultivation. This chapter first provides an overview of conventional detection methods. It then presents the potential of and various current approaches in microfluidics. The focus is on microfluidic methods for phenotypic antimicrobial susceptibility testing.

Nanofluidic Immobilization and Growth Detection of Escherichia coli in a Chip for Antibiotic Susceptibility Testing.

Infections with antimicrobial resistant bacteria are a rising threat for global healthcare as more and more antibiotics lose their effectiveness against bacterial pathogens. To guarantee the long-term effectiveness of broad-spectrum antibiotics, they may only be prescribed when inevitably required. In order to make a reliable assessment of which antibiotics are effective, rapid point-of-care tests are needed. This can be achieved with fast phenotypic microfluidic tests, which can cope with low bacterial concentrations and work label-free. Here, we present a novel optofluidic chip with a cross-flow immobilization principle using a regular array of nanogaps to concentrate bacteria and detect their growth label-free under the influence of antibiotics. The interferometric measuring principle enabled the detection of the growth of Escherichia coli in under 4 h with a sample volume of 187.2 µL and a doubling time of 79 min. In proof-of-concept experiments, we could show that the method can distinguish between bacterial growth and its inhibition by antibiotics. The results indicate that the nanofluidic chip approach provides a very promising concept for future rapid and label-free antimicrobial susceptibility tests.