HAMR: Swimming robo roach makes a splash

HAMR, the robotic amphibious roach

There have been a few insect-robots like the RoboBee and VelociRoACH that have been created in the past and the latest insect robot is the HAMR, an amphibious roach. The HAMR or the Harvard Ambulatory MicroRobot was created by Harvard University.

In 2013, the actual HAMR was created and it was tether controlled. It measures 4.4 cm long and moves at a speed of 8.4 body lengths per second. It was created by using 23 microscopic layers of material that was sandwiched together and the patterns were cut out using laser.

The latest version of the HAMR weighs 1.65 grams and features four foot-pads on the four legs. This robotic roach created by the scientists is amphibious in nature. It can walk on land as well as swim on the surface of the water. The HAMR is also designed to walk underwater as long as it is desired, enabling the robot to explore new environments.

Working of the HAMR

When the HAMR enters the water, the foot pads provide the surface tension-induced buoyancy to prevent it from sinking. There is a provision for flaps on the underside of the pads that helps it to move across the water. The HAMR moves its legs in a swimming motion at a frequency of up to 10 Hertz. When the robot moves across the surface of the water it can evade any of the obstacles present and also reduce drag. The HAMR has four pairs of asymmetric flaps and customized swimming gait that help it to swim on the surface of the water. There is an unsteady interaction created between the passive flaps of the robot and the surrounding water which enables the robot to swim forward and turn.

From the underside of the pads, the HAMR can apply electric current to the water. This is electrowetting whereby the voltage that is applied will reduce the contact angle between an object and the water surface. Due to this the surface tension breaks and the robot sinks.

The robot uses the same mechanism to walk along the bottom of the water just like it walks on land. There is a watertight coating of a polymer known as Parylene to prevent shorting of the HAMR.

In order to get onto the land the HAMR has to break through the surface. A water surface tension force which is almost twice the robotic weight pushes the robot down. There is also an induced torque that increases the friction on the hind legs of the robot. To overcome this difficulty, the scientists have stiffened the transmission of the HAMR and put soft pads to the front legs of the robot. This helps to increase the payload capacity and the friction gets redistributed to enable the robot to climb. The robot then walks up an incline and breaks out of the water surface.

There is a possibility of using technology that gets its inspiration from geckos such as the gecko-inspired adhesives or jumping mechanisms where the HAMR can come out of the water without the use of a ramp or a slope.