Bio-inspired magnetic-driven folded diaphragm for biomimetic robot

Abstract

Functional soft materials, exhibiting multiple types of deformation, have shown their potential/abilities to achieve complicated biomimetic behaviors (soft robots). Inspired by the locomotion of earthworm, which is conducted through the contraction and stretching between body segments, this study proposes a type of one-piece-mold folded diaphragm, consisting of the structure of body segments with radial magnetization property, to achieve large 3D and bi-directional deformation with inside-volume change capability subjected to the low homogeneous magnetically driving field (40 mT). Moreover, the appearance based on the proposed magnetic-driven folded diaphragm is able to be easily customized to desired ones and then implanted into different untethered soft robotic systems as soft drivers. To verify the above points, we design the diaphragm pump providing unique properties of lightweight, powerful output and rapid response, and the soft robot including the bio-earthworm crawling robot and swimming robot inspired by squid to exhibit the flexible and rapid locomotion excited by single homogeneous magnetic fields.

Fig. 1. The folded diaphragm inspired by the segment structure of earthworm.

a Bio-inspired magnetic-driven folded diaphragm from an earthworm. b Fabrication mold. c Magnetization mold of the magnetic-driven folded diaphragm. d Magnetization characteristics and operational principle of the magnetic-driven folded diaphragm with upward magnetization direction (Type+ diaphragm). e Magnetization characteristics and operational principle of the magnetic-driven folded diaphragm with downward magnetization direction (Type– diaphragm).

Fig. 2. Mechanical properties of the folded diaphragm.

a Customizable shape of the magnetic diaphragm in triangle, square, hexagon, and circular. b comparisons of deformation range between the folded and flat magnetic diaphragm under the 40 mT magnetic field by vision. c comparisons of the displacement (average value and standard deviation of 9 cycles measurement) in the top point between the folded and flat magnetic diaphragm under different magnetic fields (range from 0–40 with 5 mT increments). d comparisons of the elastic-resistance force of the diaphragm center between the folded and flat magnetic diaphragm under different displacements ranging from 0–10 mm with 1 mm increment (average value and standard deviation of 9 cycles measurement).

Fig. 3. Diaphragm pump based on the folded diaphragm.

a Schematic diagram of the single diaphragm pump. b–d The pictures of a single diaphragm under 0, 40, and –40 mT magnetic fields, respectively. e Schematic diagram of the double diaphragm pump. f–h The pictures of double diaphragms under 0, 40, and –40 mT magnetic fields, respectively. i The pump-in and pump-out pressure properties of the single diaphragm pump. j and k The ideal pump-in and pump-out flow rate properties of single diaphragm pump and double diaphragm pump, respectively. l Unidirectional fluid transfer function of the single diaphragm pump under –40 to 40 mT harmonic magnetic field with 1 Hz frequency. m Unidirectional fluid transfer function of the single diaphragm pump under –20 to 20 mT harmonic magnetic field with 5 Hz frequency.

Fig. 4. Crawling robot inspired by the earthworm.

a Schematic diagram of the single-section crawling robot. b Schematic diagram of the double-section crawling robot. c Components’ magnetization characteristics. d–f Movement patterns of single-section crawling robot under 0, 40, and –40 mT magnetic fields, respectively. g–i Movement patterns of double-section crawling robot under 0, 40, and –40 mT magnetic fields, respectively.

Fig. 5. Swimming robot inspired by squid.

a The water-filling process of squid’s mantle cavity. b The squid’s water jet propulsion. c Schematic diagram of a bionic squid swimming robot. d Magnetization characteristics of the magnetic folded diaphragm, bionic tentacles, and check valves. e Picture of cavity water filling water of bionic squid swimming robot (40 mT). f Picture of water jet of bionic squid swimming robot (–40 mT). g Sucking and h Water jetting schematic diagram of swimming process of swimming robot under the harmonic magnetic field.