Gentle gripping and smooth movement
The researchers have demonstrated several applications for these artificial muscles, one of which is a soft, miniature gripper arm. In an experiment, they were able to gently trap a zebrafish larva in water and then release it again. “It was fascinating to see just how precisely yet gently the gripper functioned; the larva swam away afterwards unharmed,” recalls Zhiyuan Zhang, a former doctoral student under Ahmed and one of the lead authors of the external page study, which has been published in Nature.
The researchers also constructed a robot that resembles a tiny stingray to demonstrate undulatory movements. It is about four centimetres wide. Two artificial muscles mimic the function of pectoral fins. When the researchers apply ultrasound stimulation, it induces undulatory motion in the muscle, enabling the miniature robot to glide through water without any cabling. “Undulatory locomotion was a real highlight for us,” says Ahmed. “It shows that we can use the microbubbles to achieve not only simple movements but also complex patterns, like in a living organism.”
Long-term prospects for these devices – dubbed “stingraybots” by the researchers – include deployment in the gastrointestinal tract, possibly to release medication with absolute precision or support minimally invasive procedures. In fact, the researchers have already considered how a stingraybot could be transported into the stomach: they propose rolling the robot up and placing it in a specially developed capsule that could be swallowed before dissolving in the patient’s stomach.