Attachment of micro- and nano-particles on tipless cantilevers for colloidal probe microscopy

Hypothesis: Current colloidal probe preparation techniques face several challenges in the production of functional probes using particles <= 5 mu m. Challenges include: glue encapsulated particles, glue altered particle properties, improper particle or agglomerate attachment, and lengthy procedures. We present a method to rapidly and reproducibly produce functional micro and nano-colloidal probes. Experimental: Using a six-step procedure, cantilevers mounted on a custom designed 45 degrees holder were used to approach and obtain a minimal amount of epoxy resin (viscosity of similar to 14,000 cP) followed by a single micron/nano particle on the apex of a tipless cantilever. The epoxy and particles were prepared on individual glass slides and subsequently affixed to a 10 x or 40x optical microscope lens using another custom designed holder. Scanning electron microscopy and comparative glue-colloidal probe measurements were used to confirm colloidal probe functionality. Findings: The method presented allowed rapid and reproducible production of functional colloidal probes (80% success). Single nano-particles were prominently affixed to the apex of the cantilever, unaffected by the epoxy. Nano-colloidal probes were used to conduct topographical, instantaneous force, and adhesive force mapping measurements in dry and liquid media conveying their versatility and functionality in studying nano-colloidal systems. (C) 2014 Elsevier Inc. All rights reserved.