Spinning-enabled wireless amphibious origami millirobot

Abstract

Wireless millimeter-scale origami robots have recently been explored with great potential for biomedical applications. Existing millimeter-scale origami devices usually require separate geometrical components for locomotion and functions. Additionally, none of them can achieve both on-ground and in-water locomotion. Here we report a magnetically actuated amphibious origami millirobot that integrates capabilities of spinning-enabled multimodal locomotion, delivery of liquid medicine, and cargo transportation with wireless operation. This millirobot takes full advantage of the geometrical features and folding/unfolding capability of Kresling origami, a triangulated hollow cylinder, to fulfill multifunction: its geometrical features are exploited for generating omnidirectional locomotion in various working environments through rolling, flipping, and spinning-induced propulsion; the folding/unfolding is utilized as a pumping mechanism for controlled delivery of liquid medicine; furthermore, the spinning motion provides a sucking mechanism for targeted solid cargo transportation. We anticipate the amphibious origami millirobots can potentially serve as minimally invasive devices for biomedical diagnoses and treatments.

Fig. 1. Mechanisms of the magnetically actuated amphibious origami robot.

a Rotational motions for on-ground omnidirectional rolling of spheres and in-water propulsion of propeller. The propeller image was reproduced with permission from Rolls-Royce. b Kresling “spheres” with high global symmetry for omnidirectional motion and locally tilted triangular panels for in-water propulsion. c Three locomotion modes, rolling, flipping, and spinning, based on the robot’s rotational motions around different axes (dashed lines) in different environments. d Image of the robot composed of a Kresling with a magnetic plate attached to it. The magnetic plate has an in-plane magnetization M. Scale bar: 2 mm. Mechanisms of (e) on-ground rolling, (f) on-ground flipping, and (g) in-water swimming actuated by a rotating magnetic field B. h Steering mechanism by changing rotation axis of B. i Pumping mechanism by cyclic folding/unfolding upon a pair of magnetic torques +T and -T.

Fig. 2. Self-adaptive on-ground locomotion and controlled delivery of liquid medicine.

a Mechanism of self-adaptive locomotion. Under the same rotating magnetic field with a frequency (f) of 4 Hz and a strength (B) of 10 mT, the robot overcomes different terrains, including (b) a wall obstacle, (c) spaced stairs, and an inclined surface by autonomously switching between rolling and flipping. d Mechanism of jumping enabled by an instant magnetic field with a strength of B and an angle of θ between magnetic field and magnetization. e Demonstration of jumping when B = 40 mT and θ = 120°. f Characterization of jumping performance. g Controlled release of liquid medicine by the magnetically actuated pumping mechanism. h Experimental images of pumping medicine. The two attached magnetic plates have the same dimensions but different in-plane magnetization directions M₁ and M₂. M_net is the net magnetization of the Kresling robot. i Controlled delivery of liquid medicine by self-adaptive locomotion and pumping in an ex vivo pig stomach. Scale bars: 5 mm.

Fig. 3. Swimming mechanisms and navigation underwater and at air–water interface.

a A right-handed propeller. b Propulsion induced from propeller-like tilted panels of the Kresling. c Modified Kresling with frontal hole and radial cuts for enhanced swimming performance. d Speed comparison of the horizontal swimming for robots with and without the hole and cuts under different magnetic field rotation frequencies. e CFD simulations for comparison of the streamlines and normalized pressures of the robots with and without the hole and cuts. Demonstrations of swimming under a rotating magnetic field with a strength of 10 mT and a frequency of 24 Hz along (f) a straight line, (g) a 2D “ ∞ ” path, and (h) a 3D spiral path. i Swimming at the air–water interface. Scale bars: 5 mm.

Fig. 4. Amphibious locomotion in hybrid terrestrial-aquatic environments and targeted cargo transportation.

a The environment model for the demonstration of amphibious locomotion and cargo transportation. b Schematics of cargo capturing via a spinning-enable sucking mechanism and cargo releasing. c The robot rolls and flips over different terrains in a self-adaptive manner. d The robot jumps over a barrier to a shallow water area, submerges into a deep water area, and swims toward the cargo to capture it. e The robot swims to the targeted position and releases the cargo. f The robot swims to the air–water interface and returns to the initial position over continuous stairs by self-adaptive locomotion. The demonstration of (g) self-adaptive on-ground rolling/flipping and (h) swimming in an ex vivo pig stomach with viscous fluid (Viscosity: 12 mPa S). Scale bars: 5 mm.