Reduction of a micro-object’s adhesion using chemical functionalisation

The adhesion and interaction properties of functionalised surfaces (substrate or cantilever) were investigated by means of atomic force microscope (AFM) related force measurements. The surfaces were functionalised with a polyelectrolyte: Poly(Allylamine Hydrochloride) (PAH), or with silanes: 3 (ethoxydimethylsilyl) propyl amine (APTES) or (3 aminopropyl) triethoxysilane (APDMES). Measurements of forces acting between a bare glass sphere (functionalised or not) and a functionalised surface indicated repulsive or attractive forces, depending on functionnalisation and medium (wet or dry). Adhesion forces (pull-off) can be observed in dry medium while in wet medium, this phenomenon can be cancelled. Now, the pull-off forces is an important problem in the automation of micro-object manipulations. The cancellation of this force by chemical functionnalisation is thus a promising way to improve micro-assembly in the future.