The present invention is directed to a microfluidic device for lysis of cells, such as bacteria and microorganisms. In particular, the present invention relates to microfluidic devices and methods of manufacture of such microfluidic devices comprising a substrate with at least one channel packed with a polymer monolith embedded with carbon particles, for example carbon nanotubes. The microfluidic devices and methods of the present invention are useful for cell lysis of cells within a biological sample, such as a untreated biological sample comprising microorganisms, such as but not limited to gram positive and gram negative bacteria. In some embodiments, the microfluidic devices of the present invention can also optionally comprise other modules enabling further processing of the biological sample, for example isolation, purification and detection of biomolecules released from the lysed cells, such as but not limited to nucleic acids or proteins or peptides from the lysed cells, providing a complete Lab-on-a-Chip analysis system for biomolecules released from difficult to lyse microorganisms in a single step or process. The microfluidic devices of the present invention can also be adapted and are useful to methods to enrich for microorganisms in a biological sample, for example enrich for a desired type of bacteria within a biological sample. The microfluidic devices and methods of the present invention can be adapted to perform highly efficient lysis of microorganisms within a biological sample for diagnostic tests, for example for diagnosis of infectious agents and pathogens, such as bacteria, viruses or parasites.