Smart Material Actuated Inkjet Printed Robotic Fish

Abstract

Several underwater activities like exploration, surveillance, measuring key characteristics like water current or temperature, and mapping seabed risk human lives as the underwater conditions are hostile. Developing underwater vehicles provides a solution to minimize risking human lives. The underwater robots developed based on conventional actuation tend to be bulky and inefficient, lacking the ability to swim through a complex environment. Using smart materials, efficient robots can be built to swim individually or in swarms through a complex environment. However, there is a huge gap in the performance of the underwater robots developed using smart materials in comparison with the ones actuated conventionally. This thesis fills the gap by elaborating on the development of a robotic fish using polyvinylidene fluoride (PVDF), a smart material, that is proven to produce higher strain per volt among other electro-active polymers (EAPs). To develop a robotic fish, different swimming styles are studied and the carangiform style is adapted to achieve good efficiency without compromising maneuverability. The robotic fish is designed as a monolithic structure with an integrated actuator. The carangiform swimming style is implemented by designing a bi-morph actuator that occupies one-third portion of the robotic fish. The actuator is designed to produce symmetric tail deflections
in the lateral direction generating the vortices in the wake which can propel the robotic fish. In order to prove the usability of the actuator underwater, uni-morph actuators were manufactured using the inkjet printing technique. The actuator samples are developed on four different substrate materials, namely PEN, 25um Kapton, 50um Kapton, and Novele each with dimensions of 60mmx20.5mm. Experiments are conducted under various conditions to test their behavior before operating them underwater. The PVDF actuators developed using the Novele substrate successfully operated underwater at an operating frequency of 5.1Hz.