Geometric Analysis and Modelling of Microfluidic Contact Angles for Design and Manufacturing of Micro Bio-Device

Yuan-Shin Lee1,a, Euiseok Kim1,b and Roger J. Narayan2

1Industrial and Systems Department, North Carolina State University Raleigh, NC 27695, U. S. A.

2Biomedical Engineering, University of North Carolina at Chapel Hill Chapel Hill, NC, U. S. A.


In this paper, a geometric analysis and modelling method is presented to calculate the contact angle of microfluidic liquid on the solid substrate to apply for micro bio-device development. To estimate the contact angle of microfluidic, we assume that liquid spreads out ideally based on the liquid surface tension and other forces, so it diffuses at equal distances in all directions. Based on this assumption, we analyze the geometry of a droplet and derived the wetting distance as the function of liquid volume, a contact angle and material properties. In the paper, we develop two models: one for large droplets and another for very tiny droplets. The large droplet considered gravitational effects in terms of material properties. To validate the estimated contact angle, a certain volume of liquid was dropped on the solid substrate, and we then measured the wetting distance of the liquid droplet. The measured wetting distance was compared with the theoretical wetting distance calculated by our analytical models. For comparison, different materials were used in experiments with goniometer for validation. The presented techniques can be used for the design and selection of machining parameters for the micro bio-devices development.

Keywords: Modelling and design, Micro bio-device, Microfluidic, Laser micro-manufacturing, Design and manufacturing.

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