1 Karthik Visvanathan, Farah Shariff, Seow Yuen Yee and Amar S. Basu Department of Mechanical Engineering, University of Michigan, Ann Arbor, USA Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, USA 指導教授：劉承賢 教授 學生：劉景文

2 Introduction Literature review Experiment Result Conclusion/future work Reference

3 Marangoni Flow The mass transfer along an interface due to surface tension gradient Liquid with a high surface tension pulls more strongly on the surrounding liquid Gradient in surface tension will naturally cause the liquid to flow away from regions of low surface tension

4 Example of Marangoni flow - Tears of wine Alcohol has a lower surface tension than water This effect is named after Italian physicist Carlo Marangoni Surface tension gradient can be caused by concentration gradient, temperature gradient, etc. Picture source: keyword : tears of wine

5 Floating mini-robot based on thermal Marangoni flow

6 Steve H. Suhr et al. designed and built the first controllable water strider robot Picture source: “Biologically Inspired Miniature Water Strider Robot” Steve H. Suhr, Yun Seong Song, Sang Jun Lee, and Metin Sitti, Member, IEEE

7 Ming Su designed a floating boat by applying drops of organic solvents to the liquid layer “Liquid mixing driven motions of floating macroscopic objects” APPLIED PHYSICS LETTERS 90,

8 A similar work using isopropyl alcohol as a propellant “Propulsion of microboats using isopropyl alcohol as a propellant” J. Micromech. Microeng. 18 (2008) (6pp)

9 Water based mini robots for environmental sensing applications and/or military applications Marangoni flow based on local thermal gradient for propulsion and steering Compared with solution based propulsion limited fuel may be a challenge Compared with propeller based propulsion noise and vibration may be a challenge In a macro system, marangoni flow is usually ignored; but in a micro system, marangoni flow becomes dominant

10 Six legged design provides three DOF of movement High temperature induces low surface tension, exerting a tangential force to propel the robot

11 Lift force increases with increasing contact angle and saturates at contact angle greater than 90 ° To increase lift force leg of the robot can be covered with a hydrophobic material

12 A 10 mm x 300 μm x 300 μm leg with a 2 mm x 200 μm x 1 μm heater Minimum gap of 10 mm between the legs required to prevent temperature gradient from one leg to affect the other

13 At 60 ℃ for each leg maximum flow velocity 15.3 mm/s propulsion force mN

14 A H-shaped structure was constructed to test the feasibility of the proposed mini-robot H-shaped robot tested in Fluorinert FC 3283 solution

15 Linear, clockwise, counter-clockwise motion of the H- shaped structure demonstrated Spot heated using a soldering iron, the structure was observed to move from regions of lower surface tension (high temperature region) to higher surface tension (low temperature region)

16 This paper reports a novel propulsion mechanism utilizing a thermal gradient based Marangoni flows Preliminary experiments demonstrate the feasibility of the proposed propulsion mechanism The actual proposed device is expected to perform better hydrophobic material will increase total lift force propulsion force can be increased by increasing temperature of the heater and the number of legs

17 Wikipedia “Biologically Inspired Miniature Water Strider Robot” Steve H. Suhr, Yun Seong Song, Sang Jun Lee, and Metin Sitti, Member, IEEE “Propulsion of microboats using isopropyl alcohol as a propellant” J. Micromech. Microeng. 18 (2008) (6pp) “Liquid mixing driven motions of floating macroscopic objects” APPLIED PHYSICS LETTERS 90, (2007)

18 Thank you for listening