MIT's robofish are now more fishlike; they have fewer moving parts than earlier, more mechanical models and more closely mimic their natural counterparts. Check the video:
(MIT's robotic fish now more natural swimmers)
The robofish bodies are continuous (i.e., not divided into different segments), flexible and made from soft polymers. This makes them more maneuverable and better able to mimic the swimming motion of real fish, which propel themselves by contracting muscles on either side of their bodies, generating a wave that travels from head to tail.
"Most swimming techniques can be copied by exploiting natural vibrations of soft structures," says MIT mechanical engineer Valdivia Y Alvarado.
As part of his doctoral thesis, Valdivia Y Alvarado created a model to calculate the optimal material properties distributions along the robot's body to create a fish with the desired speed and swimming motion.
The MIT team is the only one using controlled vibrations of flexible bodies to mimic biological locomotion.
"With these polymers, you can specify stiffness in different sections, rather than building a robot with discrete sections," says MIT mechanical engineer Kamal Youcef-Toumi. "This philosophy can be used for more than just fish" - for example, in robotic prosthetic limbs.