And Yet it Moves! Microfluidics Without Channels and Troughs |
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Authors: | Francesca Lugli Giulia Fioravanti Denise Pattini Luca Pasquali Monica Montecchi Denis Gentili Mauro Murgia Zahra Hemmatian Massimiliano Cavallini Francesco Zerbetto |
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Affiliation: | 1. Dipartimento di “Chimica G. Ciamician”, Università di Bologna, V. F. Selmi 2, 40126 Bologna, Italy;2. Department of Physical and Chemical Sciences, University of L'Aquila, Via Vetoio 1, 67100 L'Aquila, Italy;3. IOM‐CNR‐, S.S. 14, Km. 163.5, Basovizza, 34149 Trieste Italy and Dipartimento di Ingegneria, Università di Modena e Reggio Emilia, Via Vignolese 905, 41125 Modena, Italy;4. Istituto per lo Studio dei Materiali Nanostrutturati (ISMN), Consiglio Nazionale delle Ricerche (CNR), Via P. Gobetti 101 40129 Bologna, Italy |
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Abstract: | A simple, versatile, rapid, and inexpensive procedure based on the immersion method is developed to fabricate chemical gradients on chemically activated Si/SiO2 surfaces by a trichloro (1H,1H,2H,2H‐perfluorooctyl) silane self‐assembly monolayer (SAM). Contact angle measurements, atomic force microscopy, and X‐ray photoelectron spectroscopy data based on the intensity of the signals of C1s and F1s, which progressively increase, indicate that the surface is characterized by the presence of increasing amounts of the SAM along the gradient direction. Experimental conditions are optimized by maximizing the variation of the contact angle of water drops at the starting and the ending points of the gradient. The application of the chemical gradient to droplet motion is demonstrated. The results are rationalized by dissipative particle dynamics simulations that well match the observed contact angles and the velocities of the drops. The simulations also show that the intrinsic nature of the gradient affects the velocity of the motion. |
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Keywords: | surface modification self‐assembly functional coatings chemical gradients modelling |
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