Directed assembly of nanoparticles into continuous microstructures by standing surface acoustic waves

Haim Sazan, Silvia Piperno, Michael Layani, Shlomo Magdassi, Hagay Shpaisman*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

45 Scopus citations


Directed-assembly by standing surface acoustic waves (SSAWs) only requires an acoustic contrast between particles and their surrounding medium. It is therefore highly attractive as this requirement is fulfilled by almost all dispersed systems. Previous studies utilizing SSAWs demonstrated mainly reversible microstructure arrangements from nanoparticles. The surface chemistry of colloids dramatically influences their tendency to aggregate and sinter; therefore, it should be possible to form permanent microstructures with intimate contact between nanoparticles by controlling this property. Dispersed silver nanoparticles in a microfluidic channel were exposed to SSAWs and reversibly accumulated at the pressure nodes. We show that addition of chloride ions that remove the polyacrylic capping of the nanoparticles trigger their sintering and the formation of stable conducting silver microstructures. Moreover, if the destabilizing ions are added prior to nanoparticle assembly while continuously streaming the dispersion through the acoustic aperture, the induced aggregation leads to formation of significantly thinner microstructures, which are (for the first time) unlimited in length by the acoustic apparatus. This new approach overcomes the discrepancy between the need for organic dispersants to prevent unwanted aggregation in the dispersion, and the end product's requirement for intimate contact between the colloidal particles.

Original languageAmerican English
Pages (from-to)701-709
Number of pages9
JournalJournal of Colloid and Interface Science
StatePublished - 15 Feb 2019

Bibliographical note

Publisher Copyright:
© 2018 Elsevier Inc.


  • Acoustic manipulation
  • Conductive microstructures
  • Directed assembly
  • Micro patterning
  • Nanoparticle sintering
  • Stabilized nanoparticles


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