Backswimmer‐Inspired Miniature 3D‐Printed Robot with Buoyancy Autoregulation through Controlled Nucleation and Release of Microbubbles

Abstract

The backswimmer is an aquatic insect, capable of regulating its buoyancy underwater. When it enters the water, it entraps an air bubble in a superhydrophobic hairy structure covering its abdomen. While this bubble is mainly used for respiration, it also functions as an external inflatable gas reservoir for buoyancy regulation. Namely, hemoglobin is used to store and release oxygen to the entrapped bubble, reversibly. This way, it can reach neutral buoyancy without further energy consumption. Herein, a small, centimeter‐scale, backswimmer‐inspired untethered robot (BackBot) with autobuoyancy regulation through controlled nucleation and release of microbubbles is developed. The bubbles nucleate and grow directly on onboard electrodes through electrolysis, regulated by low voltage. A bubble‐entrapping 3D‐printed canopy is introduced to create a stable external gas reservoir. To reduce buoyancy forces, the bubbles are released through linear mechanical vibrations of the canopy, decoupled from the robot's body. Through pressure sensing and a proportional integral derivative control loop mechanism, the robot autoregulates its buoyancy to reach neutral floatation underwater within seconds. This mechanism can promote the replacement of traditional, and physically larger, buoyancy regulation systems such as pistons and pressurized tanks, and enables the miniaturization of autonomous underwater vehicles.

Emergent clustering due to quorum sensing interactions in active matter

“…To overcome the statistical gap, one can examine the interactions over an extended duration of time, or to repeat the physical experiments multiple times. An existing robotic platform, capable of autonomous regulation of vertical buoyancy [74], can be adapted to introduce propulsion in the horizontal plane. This will initially enable to study cooperative phenomena due to quorum sensing based interactions in 2D, either at the water-air interface for positively buoyant robotic swimmers or in a specific plane underwater for neutrally buoyant swimmers.…”

Recent Advances on Underwater Soft Robots

“…It controls partial buoyancy wirelessly by using a soft thermoelectric (TE) pneumatic actuator (TPA), which, in turn, mimics the intermittent locomotive gliding and turning in the water. Dror Kobo et al [ 240 ] developed a small, centimeter‐sized, backswimmer‐inspired untethered robot (BackBot) which regulates self‐buoyancy by controlling nucleation and release of microbubbles. This mechanism could facilitate the replacement of traditional, physically larger buoyancy regulation systems, such as pistons and pressurized tanks, and enable miniaturization of autonomous underwater vehicles.…”

“…It controls partial buoyancy wirelessly by using a soft thermoelectric (TE) pneumatic actuator (TPA), which, in turn, mimics the intermittent locomotive gliding and turning in the water. Dror Kobo et al [240] developed a small, centimeter-sized, backswimmer-inspired untethered robot (BackBot) which regulates self-buoyancy by controlling nucleation and release of microbubbles. This mechanism could facilitate the replacement Quadrupeds-inspired robot 0.37 [397] Soft jumper 6 [226] Crawling and walking Fluidic soft robotic snake 0.07 [18] PATRICK 0.04 [227] Worm-inspired robot 0.025 [82] Crab-inspired soft robot 0.234 [228] Flow-sensing walking robot 0.1 [316] Amphibious soft robot 1.6 [9] 3D printed robot 0.06 [398] Coconut octopusinspired robot 0.603 [326] Swimming Hydrodynamically driven Madeleine 0.95 [224] Spine-inspired robotic fish 0.78 [225] Piezoelectric fish 0.03 [223] SoFi 0.5 [80] FEA-driven robotic fish 0.44 [12] Tunabo 1.6 [313] Pneumatic-actuated manta robot 0.67 [116] PMC robotic cownose ray 0.033 [310] Rowing OCTOPUS 0.27 [17] ART 0.087 [8] PoseiDRONE 7.964 [399] Sea snailfish 0.45 [15] Robotic octopus 0.26 [309] Wave undulating DE-driven eel larva 0.0086 [64] Pneumatic-actuated eel robot 0.36 [348] FEA-driven eel robot 0.12 [66] Magnetic soft robot 0.47 [400] Jet-propelled Cephalopod-inspired SUUV 1.5 [243] Squid-like aquatic-aerial robot 43.9 [222] BUVMS with long-fin propulsion 0.23 [401] Cephalopod-inspired CPHJE 1.8 [402] RoboScallop 2.0 [325] of traditional, physically larger buoyancy regulation systems, such as pistons and pressurized tanks, and enable miniaturization of autonomous u...…”

Developments and Challenges of Miniature Piezoelectric Robots: A Review

“…In recent decades, miniature robots have attracted considerable attention in academic and industry due to their highlight features, including small size, light weight, low cost, and agile movement, [1][2][3][4][5] compared with middle or large robots. [6][7][8] Miniature robots here refer to the robots with a characteristic size (body length) less than 100 mm (commonly from a few millimeters to a few centimeters).…”