Direct measurement of the binding force between microfabricated particles and a planar surface in aqueous solution by force-sensing piezoresistive cantilevers

Hiroaki Onoe, Murat Gel, Kazunori Hoshino, Kiyoshi Matsumoto, Isao Shimoyama

Research output: Contribution to journalArticle

12 Citations (Scopus)


We propose a force measurement method for evaluating the binding force between microscale flat surfaces in an aqueous solution. Using force-sensing piezoresistive cantilevers with sub-nanonewton force resolution, we have directly measured binding forces between SiO 2-SiO 2 microcontacts, which were created by gravity-driven random collision between microfabricated SiO 2 cylindrical particles and a planar SiO 2 substrate in a HCl solution. First, to examine our method we measured the pH dependence of the binding force. The binding forces were 12 and 5.8 nN at pH 1.0 and 2.0, respectively. As the pH increased, the binding force decreased and became zero at pH greater than 3.0. We confirmed that the bindings were based on the van der Waals' (VDW) force at pH 2.0 or less whereas a repulsive double-layer force acted between the surfaces at pH 3.0 or more. Second, the binding forces were categorized into a friction force or an adhesion force between the particles and the substrate. In the measurement, the friction force between the particle and the substrate was measured in the case when the particle slid on the substrate. On the contrary, the adhesion force was measured when the particle came off the substrate. Whether the particle slid or came off depended on the aspect ratio of the particle. We fabricated cylindrical particles with an aspect ratio of 0.03-2.0 and distinguished the friction force from the adhesion force by changing the aspect ratio of the particles. As a result, the friction force per unit contact area between SiO 2- SiO 2 flat surfaces was found to be 330 pN/μm 2 ∼ 20% when we used particles with a low aspect ratio (<0.1), and the adhesion force per unit contact area was 90 pN/μm2 ± 20% for particles with a high aspect ratio (>0.4). For fluidic self-assembly that utilizes microscale surface contact in a liquid, our measurement method is an effective tool for studying and developing systems.

Original languageEnglish
Pages (from-to)11251-11261
Number of pages11
Issue number24
Publication statusPublished - 2005 Nov 22
Externally publishedYes


ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry

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