Deterministic particle assembly on nanophotonic chips

Razie Khalesi Moghaddam, Nikhil Bhalla, Amy Q. Shen, Giovanniantonio Natale

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Controlled particle assembly from a dilute suspension droplet is challenging yet important for many lab-on-a-chip and biosensing applications. The formation of hot spots on the localized surface plasmonic resonance (LSPR) substrates induced by laser excitation can generate microbubbles. These microbubbles, upon the laser removal, shrink and collapse due to electron energy dissipation, leading to guided particle assembly on the LSPR substrate.

After depositing dilute silica particles dispersions on both nanoisland (AuNI) and planar gold (Au) plasmonic substrates (referred to as LSPR and SPR substrates respectively), microbubbles were formed when a laser beam was applied. Particle dispersion concentration, laser power, and the radius of circular laser sequence were varied to produce different sizes of particle clusters on the LSPR substrate after bubble shrinkage upon the laser removal. To stabilize the assembled structures over time, sodium chloride (NaCl) was ad ded to the dispersions.

Even though thermo-plasmonic flow and microbubbles can be produced with SPR substrates, particle assembly is only possible on LSPR substrates because of electron energy dissipation via nanoscale air gaps trapped in the LSPR substrate. By tuning the laser power, the radius of the circular laser sequence, and the particle dispersion concentration, the number of particles in the assembled structure can be controlled. The addition of NaCl to the dispersion can screen the electrostatic charges among the particles and between the particles and substrate, favoring hydrogen bonding and stabilizing the assembled structures for hours. These findings establish a new framework for utilizing nanophotonic chips where particle assembly can be achieved by a single source of light.
Original languageEnglish
Pages (from-to)259-269
Number of pages11
JournalJournal of Colloid and Interface Science
Early online date23 Jun 2021
Publication statusPublished (in print/issue) - 31 Dec 2021

Bibliographical note

Funding Information:
R.K. and G.N. acknowledge the support of the Canada First Research Excellence Fund (CFREF) and of the Natural Sciences and Engineering Research Council of Canada (NSERC), [funding reference number 03783 ]. A.Q.S. acknowledges the support of the Okinawa Institute of Science and Technology Graduate University (OIST) with subsidy funding from the Cabinet Office, Government of Japan. A.Q.S also acknowledges funding from the Joint Research Projects (JRPs) supported by JSPS and SNSF. Authors would like to thank Mr. Kang-Yu Chu from OIST for his help with SEM imaging.

Publisher Copyright:
© 2021 Elsevier Inc.


  • Bubble shrinkage
  • Hot spot formation
  • Nanophotonic chips
  • Self-assembly
  • Surface plasmonic resonance


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