By Chia-Yuan Chen*, Cheng-Yi Lin, And

Supplementary Material

“Inducing3D vortical flow patterns with 2D asymmetric actuation of artificial cilia for high performance active micromixing”

by Chia-Yuan Chen*, Cheng-Yi Lin, and

Ya-Ting Hu

Department of Mechanical Engineering, National Cheng Kung University

*To whom correspondence should be addressed.

*E-mail:; Tel:+886-6-2757575-62169.

The electronic supplementary material includes the following: (1)Motion characterizations of the fabricated artificial cilia, (2) validation of µPIV method, and (3) validation of the 3D numerical modeling method.

(1) Motion characterizations of the fabricated artificial cilia: The schematic layout of the magnetic coil system and the orientation of each artificial cilium are illustrated in Fig. S1(a). The orientation change of the artificial cilium with the direction change of the applied magnetic field is provided in Fig. S1(b). A linear relationship with R2 over 0.99 was calculated. This result demonstrated that an accurate motion control of artificial cilium can be achieved through the control of the applied magnetic field using the presented magnetic coil system. In addition, the change of tip displacement of the artificial cilium under the influence of the applied magnetic field is presented in Fig. S1(c). The beating area of artificial cilium can be controlled precisely through the control of the applied voltage using the magnetic coil system as the tip displacement increases linearly with the increase of the applied magnetic field. The relation of rotational speed with the rotational radius of the artificial cilium under the influence of magnetic field is shown in Fig. S1(d). The rotational radius reduced to an asymptotic value (approximately 40µm) when the rotational speed is faster than 30Hz.

Fig. S1 Characterizations of the magnetically actuated artificial cilia. (a) Schematic illustration of the magnetic actuation system and the micromixer with artificial cilia integrated. (b) Orientation change of the artificial cilium in response to the change of the applied magnetic field. (c) Displacement of the artificial cilium linearly proportional to the applied voltage(Chen et al. 2013).(d) Relationship between the rotational speed and radius of the artificial cilium(Chen et al. 2013).

(2) Validation of the µPIV method: The measured and calculated instantaneous flow fields by µPIV were compared with the theoretical solutions to provide information on the accuracy of the presented flow quantification technique.The theoretical solutions were derived from previous literature(Lima et al. 2009). The flow field comparison was conducted at z = 300 µm from the bottom wall (same as the artificial cilium height). Flow rate was set at 2 µL/min. Acquired µPIV velocity profiles of three locations along the microchannel length were averaged. Error bars indicate one standard deviation value of the averaged velocity profile.

Fig. S2Comparison between the velocity profiles acquired by µPIV and the theoretical solutions.

(3) Validation of the 3D numerical modeling method: Induced vortical structures acquired by µPIV were compared with numerical results under identical initial and boundary conditions. The results showed that the vorticity distribution obtained by the 3D numerical modeling method matched well with that by the µPIV method. This agreement can serve as a good basis of accuracy for the further applications of this numerical method in examining out-of-plane velocity fields, which cannot be achieved using the presented µPIV method.

Fig.S3 Comparison between the vorticity distribution obtained by µPIV (first row) and that by 3D numerical modeling (second row) at four distinct time points. Dark arrows represent in-plane velocity vectors.

References:

Chen CY, Chen CY, Lin CY, Hu YT (2013) Magnetically actuated artificial cilia for optimum mixing performance in microfluidics. Lab Chip 13(14):2834–2839

Lima R, Ishikawa T, Imai Y, Takeda M, Wada S, Yamaguchi T (2009) Measurement of individual red blood cell motions under high hematocrit conditions using a confocal micro-PTV system. Ann Biomed Eng 37(8):1546-1559