The needle-free delivery of liquid jets into soft and heterogeneous substrates, e.g. human tissue, is hindered by the need to reach specific penetration depths with energy efficient means, the break-up of jets that impedes control over liquid splash-back after impacting the substrate that cause cross-contamination between injections, and the dose delivery. These issues are faced by many applications, particularly the delivery of drugs or cosmetic products.
The main objective of this project was to achieve a fundamental understanding of liquid jets injection on soft substrates. We have generated new knowledge in the fields of microfluidics, physics, and bioengineering. These, combined, have started to open new ways to improve injection phenomena, e.g. in the delivery of drugs, dermatologic applications and other industries. This project has studied the energy partition between the input laser energy, creation of bubbles, the formation of liquid jets, and the penetration of these jets into soft substrates. We have found new ways to control cavitation within microfluidic confinement, tune the rheology of jets emerging from confined cavitation. As a result, we have unveiled new relationships between fluid dynamics and material properties governing jet injection into soft substrates. The original ambition to probe the rheological properties of jets made of biocompatible additives has been more difficult to materialize. However, the results are promising and have helped to clarify the path forward.
To conclude, this project has been a success in several aspects, covering the fundamental research, application of findings to solve societal relevant problems, and in the training of young researchers. Currently, FlowBeams, a spin-off company from the University of Twente is taking further steps in developing a portable energy-efficient injection platform that could help quantifying injections with experimental resolutions below the microsecond and micrometer scales.
