Why we should mimic jellyfish for efficient underwater propulsion

Cyro – biomimic jellyfish robot

Guns? I thought this was bioE! Why does a gun recoil? How is a submarine propelled?

How does a jellyfish propel itself?

(Naïve?) Propulsion Model j-u Time = t Time = t+  t u M V u+  u M -  m V-  V

Model v. Experiment Little jellyfish (prolates) Big jellyfish (oblates) Big 

Vortex complexes Increase Efficiency

Biomimetic Robot Design Features to replicate? How to do this simply? Bell material properties: buoyancy, elasticity Bell geometry/deformation Muscles/Actuation

Hard body vs. soft-body Finite degrees of freedom (DOF) Infinite degrees of freedom (DOF)

Action and Reaction: SMAs Shape Memory Alloys (SMA) Stress, strain and heating

Crystal structure phase change Temperature induced phase change: Martensite: soft, plastic, easily deformable state Austenite: much harder material, rigid/difficult to deform.

Reaction: Spring steel and elastomer SMA changes length metal does not

3-D printed mold: Integrating actuators

The devil in the details No-flaps Flaps

Computer control: Feedback SMA contracts  Changing resistance  Monitored by computer  Adjusts current flow through SMA

Mimic vs. Nature

Up, up, and away

Small modifications go a long way! Flaps and segments lead to large increased in thrust

References Jellyfish Propulsion Mechanisms S. Colin and J. Costello. Morphology, swimming performance and propulsive mode of six co-occuring hydromedusae. J. Exp Biol. 205 (2002) J. Dabiri et al. Flow patterns generated by oblate medusan jellyfish: field measurements and laboratory analyses. J. Exp Biol. 208 (2005) Bioinspired Jellyfish Robot (Robojelly) A. Villanueva et al. A biomimetic robotic jellyfish (Robojelly) actuated by shape memory alloy composite actuators. Bioinsp. Biomim 6 (2011) A. Villanueva et al. A bio-inspired shape memory alloy composite (BISMAC) actuator. Smart Mater. Struct. 19 (2010)