Periodic Reporting for period 4 - NanoPacks (NanoPacks: Assembling nanoparticles via evaporation-driven droplet collapse for ultrasensitive detection techniques)
Berichtszeitraum: 2021-02-01 bis 2022-01-31
Relying on the tools employed by surface enhanced Raman spectrometric techniques, we aim to assemble metallic plasmonic nanoparticles in microscopic structures that would embed passively the analytes of interest. We envision to embed them passively by assembling the plasmonic structure and the adsorption of the analytes via an evaporation-driven process, that would assemble both: the analyte and the detector at the same time.
We actively work on different methods in which we can assemble such systems in simple and affordable ways: droplet-based microfluidics, droplet deposition on superhydrophobic substrates and our newly developed gellified emulsions.
A more sophisticated line of research involves the use of microfluidic devices, not only to generate the particle assembly, but also to monitor it under the microscopy at high-resolution. We have now setup a system in which we can evaporate droplets at a very controlled rate, and most importantly, to visualize their interior to see how the assembly of particles take place. We have studied how the evaporation/dissolution of droplets in such systems occur. Due to the presence of more complex boundary conditions, the process needed to be modelled numerically, which gives very good comparison with the theory. Small clusters of particles have been already produced, and we are currently working on studying how the assembly occurs with Brownian particles confined in the picoliter droplet.
Departing from spherically-shaped droplets, by a collaboration with micro/nano-fabrication groups at the University of Twente in NanoLab, we are currently exploring the possibility of depositing clusters of nanoparticles on micro-structured substrates. A much more practically simpler, but fundamentally more challenging is the particle assembly at droplet/air interfaces: this line of work relies on the adsorption of particles at liquid/air interfaces in order to create a monolayer of nanoparticles which can then be employed for detection techniques. The approach is completely different than the other lines. We have been recently studying how particles agglomerate at the interface during the evaporation of sessile droplets, and on how the presence of salts enhances such a process.