2009/1/6 Sensing and Actuation in Miniaturized systems Final report Hello everyone !!!!! I am Wu Chih-Wei !!!!!

2009/1/6

Outline Introduction Fabrication System setup Results and discussion Conclusion

2009/1/6 Outline Introduction Fabrication System setup Result and discussion Conclusion

2009/1/6 ACTUATED BY EWOD PIV INVESTIGATION OF 3-DIMENSIONAL FLOW IN DROPS Introduction The change in contact angle due to an applied potential difference between solid and liquid EWOD = Electrowetting-On-Dielectric

2009/1/6 PIV INVESTIGATION OF 3-DIMENSIONAL FLOW IN DROPS Introduction PIV = Particle Image Velocimetry Flow direction mirror Laser x y tt’ Image plane

2009/1/6 Introduction PIV measurement in micro-channel flow!

2009/1/6 Outline Introduction Fabrication System setup Result and discussion Conclusion

2009/1/6 Fabrication cytop fluoropolymer SiO2 ITO Glass wafer droplet Secure seal FEATURES ： Leak-proof chambers are temperature resistant and eliminate evaporation

2009/1/6 Outline Introduction Fabrication System setup Result and discussion Conclusion

2009/1/6 System setup μPIV system EWOD droplet actuation system

2009/1/6 System setup 2D velocity field near the mid-height of the drop

2009/1/6 Outline Introduction Fabrication System setup Result and discussion Conclusion

2009/1/6 Result and discussion 50um 100um 150um 200um 250um 300um 350um Entire stack of 2D velocity fields computing Continuity equation (Local form of conservation equation) Side view of the Droplet Image plane 3D VELOCITY FIELDS!!!!

2009/1/6 Result and discussion A strong downward flow due to the eletro-wetting from the bottom substrate is observed near the nose of the droplet

2009/1/6 Result and discussion To understand net effect of the forward-back motions on mixing within the droplet Measure the overall displacement of the first image from all PIV image pairs Forward-back motion is inefficient for droplet mixing!! (reverse motion return the particles near their initial position)

2009/1/6 Outline Introduction Fabrication System setup Result and discussion Conclusion

2009/1/6 Conclusion 1 、 Our experimental finding shows the flow in a 3D droplet indeed deviates significantly from the parabolic flow profile used in current flow simulations 2 、 It would be desirable to develop a reduced dimension model that is computationally tractable while preserving the essential information about the 3D velocity 3 、 Due to the reversibility of the flow, a simple forward-back motion is inefficient for mixing, effective mixing has to be accomplished through irreversible movements.

2009/1/6 THANK YOU FOR YOUR ATTENTION!!!!

Bonus Information! Max Velocity ： 120 um/s UpMiddledown 100µm Channel wall 100 µm Experimental Data by Y.L.Lin 2007