Electrical Stimulation of Coleopteran Muscle for Initiating Flight

Hovering flight regulation of pigeon robots in laboratory and field

Compared to traditional bio-mimic robots, animal robots show superior locomotion, energy efficiency, and adaptability to complex environments but most remained in laboratory stage, needing further development for practical applications like exploration and inspection. Our pigeon robots validated in both laboratory and field, tested with an electrical stimulus unit (2-s duration, 0.5 ms pulse width, 80 Hz frequency). In a fixed stimulus procedure, hovering flight was conducted with 8 stimulus units applied every 2 s after flew over the trigger boundary. In a flexible procedure, stimulus was applied whenever they deviated from a virtual circle, with pulse width gains of 0.1 ms or 0.2 ms according to the trajectory angle. These optimized protocols achieved a success hovering rate of 87.5% and circle curvatures of 0.008 m-1-0.024 m-1, largely advancing the practical application of animal robots.

Recent advances in neurotechnology-based biohybrid robots

Biohybrid robots retain the innate biological characteristics and behavioral traits of animals, making them valuable in applications such as disaster relief, exploration of unknown terrains, and medical care. This review aims to comprehensively discuss the evolution of biohybrid robots, their key technologies and applications, and the challenges they face. By analyzing studies conducted on terrestrial, aquatic, and aerial biohybrid robots, we gain a deeper understanding of how these technologies have made significant progress in simulating natural organisms, improving mechanical performance, and intelligent control. Additionally, we address challenges associated with the application of electrical stimulation technology, the precision of neural signal monitoring, and the ethical considerations for biohybrid robots. We highlight the importance of future research focusing on developing more sophisticated and biocompatible control methods while prioritizing animal welfare. We believe that exploring multimodal monitoring and stimulation technologies holds the potential to enhance the performance of biohybrid robots. These efforts are expected to pave the way for biohybrid robotics technology to introduce greater innovation and well-being to human society in the future.

The Walking Control of a Crab Biorobot in Amphibious Environment

This article describes development of a crab biorobot that is capable of traversing diverse environments including both land and water. We have transformed a living rainbow crab into a walking biorobot by attaching wireless controller. An anatomical and physiological investigation revealed the rainbow crabs have sensory system on the carapace. Based on this finding, we implanted electrodes into the carapace. The walking direction of the robot is controlled through electrical stimulation provided by the controller. Depending on this site, the crab biorobot is induced to walk forward, leftward, and rightward in both terrestrial and underwater conditions. There is no significant difference in the mean walking direction between the two conditions. Smooth transition from land to water of the crab biorobot further demonstrates the adaptability to amphibious environment. This biorobot is compact, measuring 5 cm in carapace and weighing 50 g including the wireless controller. The crab biorobot in this scale has a potential for application narrow and unstructured in waterfront environments.

Amygdala electrical stimulation for operant conditioning in rat navigation

There have been several attempts to navigate the locomotion of animals by neuromodulation. The most common method is animal training with electrical brain stimulation for directional cues and rewards; the basic principle is to activate dopamine-mediated neural reward pathways such as the medial forebrain bundle (MFB) when the animal correctly follows the external commands. In this study, the amygdala, which is the brain region responsible for fear modulation, was targeted for punishment training. The brain regions of MFB, amygdala, and barrel cortex were electrically stimulated for reward, punishment, and directional cues, respectively. Electrical stimulation was applied to the amygdala of rats when they failed to follow directional commands. First, two different amygdala regions, i.e., basolateral amygdala (BLA) and central amygdala (CeA), were stimulated and compared in terms of behavior responses, success and correction rates for training, and gene expression for learning and memory. Then, the training was performed in three groups: group R (MFB stimulation for reward), group P (BLA stimulation for punishment), and group RP (both MFB and BLA stimulation for reward and punishment). In group P, after the training, RNA sequencing was conducted to detect gene expression and demonstrate the effect of punishment learning. Group P showed higher success rates than group R, and group RP exhibited the most effective locomotion control among the three groups. Gene expression results imply that BLA stimulation can be more effective as a punishment in the learning process than CeA stimulation. We developed a new method to navigate rat locomotion behaviors by applying amygdala stimulation.

A biomechanical model for the relation between bite force and mandibular opening angle in arthropods

Bite forces play a key role in animal ecology: they affect mating behaviour, fighting success, and the ability to feed. Although feeding habits of arthropods have a significant ecological and economical impact, we lack fundamental knowledge on how the morphology and physiology of their bite apparatus controls bite performance, and its variation with mandible gape. To address this gap, we derived a biomechanical model that characterizes the relationship between bite force and mandibular opening angle from first principles. We validate this model by comparing its geometric predictions with morphological measurements on the muscoloskeletal bite apparatus of Atta cephalotes leaf-cutter ants, using computed tomography (CT) scans obtained at different mandible opening angles. We then demonstrate its deductive and inductive utility with three examplary use cases: Firstly, we extract the physiological properties of the leaf-cutter ant mandible closer muscle from in vivo bite force measurements. Secondly, we show that leaf-cutter ants are specialized to generate extraordinarily large bite forces, equivalent to about 2600 times their body weight. Thirdly, we discuss the relative importance of morphology and physiology in determining the magnitude and variation of bite force. We hope that a more detailed quantitative understanding of the link between morphology, physiology, and bite performance will facilitate future comparative studies on the insect bite apparatus, and help to advance our knowledge of the behaviour, ecology and evolution of arthropods.

[Design and preliminary application of outdoor flying pigeon-robot]

Control at beyond-visual ranges is of great significance to animal-robots with wide range motion capability. For pigeon-robots, such control can be done by the way of onboard preprogram, but not constitute a closed-loop yet. This study designed a new control system for pigeon-robots, which integrated the function of trajectory monitoring to that of brain stimulation. It achieved the closed-loop control in turning or circling by estimating pigeons' flight state instantaneously and the corresponding logical regulation. The stimulation targets located at the formation reticularis medialis mesencephali (FRM) in the left and right brain, for the purposes of left- and right-turn control, respectively. The stimulus was characterized by the waveform mimicking the nerve cell membrane potential, and was activated intermittently. The wearable control unit weighted 11.8 g totally. The results showed a 90% success rate by the closed-loop control in pigeon-robots. It was convenient to obtain the wing shape during flight maneuver, by equipping a pigeon-robot with a vivo camera. It was also feasible to regulate the evolution of pigeon flocks by the pigeon-robots at different hierarchical level. All of these lay the groundwork for the application of pigeon-robots in scientific researches.

Biohybrid robots: recent progress, challenges, and perspectives

The past ten years have seen the rapid expansion of the field of biohybrid robotics. By combining engineered, synthetic components with living biological materials, new robotics solutions have been developed that harness the adaptability of living muscles, the sensitivity of living sensory cells, and even the computational abilities of living neurons. Biohybrid robotics has taken the popular and scientific media by storm with advances in the field, moving biohybrid robotics out of science fiction and into real science and engineering. So how did we get here, and where should the field of biohybrid robotics go next? In this perspective, we first provide the historical context of crucial subareas of biohybrid robotics by reviewing the past 10+ years of advances in microorganism-bots and sperm-bots, cyborgs, and tissue-based robots. We then present critical challenges facing the field and provide our perspectives on the vital future steps toward creating autonomous living machines.

Experimental Verification on Steering Flight of Honeybee by Electrical Stimulation

The artificial locomotion control strategy is the fundamental technique to ensure the accomplishment of the preset assignments for cyborg insects. The existing research has recognized that the electrical stimulation applied to the optic lobes was an appropriate flight control strategy for small insects represented by honeybee. This control technique has been confirmed to be effective for honeybee flight initiation and cessation. However, its regulation effect on steering locomotion has not been fully verified. Here, we investigated the steering control effect of honeybee by applying electrical stimulation signals with different duty cycles and frequencies on the unilateral optic lobes and screened the stimulus parameters with the highest response successful rate. Moreover, we confirmed the effectiveness of steering control by verifying the presence of rotation torque on tethered honeybees and the body orientation change of crawling honeybees. Our study will contribute some reliable parameter references to the motion control of cyborg honeybees.

In vivo closed-loop control of a locust's leg using nerve stimulation

Activity of an innervated tissue can be modulated based on an acquired biomarker through feedback loops. How to convert this biomarker into a meaningful stimulation pattern is still a topic of intensive research. In this article, we present a simple closed-loop mechanism to control the mean angle of a locust’s leg in real time by modulating the frequency of the stimulation on its extensor motor nerve. The nerve is interfaced with a custom-designed cuff electrode and the feedback loop is implemented online with a proportional control algorithm, which runs solely on a microcontroller without the need of an external computer. The results show that the system can be controlled with a single-input, single-output feedback loop. The model described in this article can serve as a primer for young researchers to learn about neural control in biological systems before applying these concepts in advanced systems. We expect that the approach can be advanced to achieve control over more complex movements by increasing the number of recorded biomarkers and selective stimulation units.

A Cyborg Insect Reveals a Function of a Muscle in Free Flight

While engineers put lots of effort, resources, and time in building insect scale micro aerial vehicles (MAVs) that fly like insects, insects themselves are the real masters of flight. What if we would use living insect as platform for MAV instead? Here, we reported a flight control via electrical stimulation of a flight muscle of an insect-computer hybrid robot, which is the interface of a mountable wireless backpack controller and a living beetle. The beetle uses indirect flight muscles to drive wing flapping and three major direct flight muscles (basalar, subalar, and third axilliary (3Ax) muscles) to control the kinematics of the wings for flight maneuver. While turning control was already achieved by stimulating basalar and 3Ax muscles, electrical stimulation of subalar muscles resulted in braking and elevation control in flight. We also demonstrated around 20 degrees of contralateral yaw and roll by stimulating individual subalar muscle. Stimulating both subalar muscles lead to an increase of 20 degrees in pitch and decelerate the flight by 1.5 m/s² as well as an induce in elevation of 2 m/s².

A review: Learning from the flight of beetles

Some Coleoptera (popularly referred to as beetles) can fly at a low Reynolds number with their deployable hind wings, which directly enables a low body weight-a good bioinspiration strategy for miniaturization of micro-air vehicles (MAVs). The hind wing is a significant part of the body and has a folding/unfolding mechanism whose unique function benefits from different structures and materials. This review summarizes the actions, factors, and mechanisms of beetle flight and bioinspired MAVs with deployable wings. The elytron controlled by muscles is the protected part for the folded hind wing and influences flight performance. The resilin, the storage material for elasticity, is located in the folding parts. The hind wings' folding/unfolding mechanism and flight performance can be influenced by vein structures of hollow, solid and wrinkled veins, the hemolymph that flows in hollow veins and its hydraulic mechanism, and various mechanical properties of veins. The action of beetle flight includes flapping flight, hovering, gliding, and landing. The hind wing is passively deformed through force and hemolymph, and the attack angle of the hind wing and the nanomechanics of the veins, muscles and mass body determine the flight performance. Based these factors, bioinspired MAVs with a new deployable wing structure and new materials will be designed to be much more effective and miniaturized. The new fuels and energy supply are significant aspects of MAVs.

Remote radio control of insect flight reveals why beetles lift their legs in flight while other insects tightly fold

In the research and development of micro air vehicles, understanding and imitating the flight mechanism of insects presents a viable way of progressing forward. While research is being conducted on the flight mechanism of insects such as flies and dragonflies, research on beetles that can carry larger loads is limited. Here, we clarified the beetle midlegs' role in the attenuation and cessation of the wingbeat. We anatomically confirmed the connection between the midlegs and the elytra. We also further clarified which pair of legs are involved in the wingbeat attenuation mechanism, and lastly demonstrated free-flight control via remote leg muscle stimulation. Observation of multiple landings using a high-speed camera revealed that the wingbeat stopped immediately after their midlegs were lowered. Moreover, the action of lowering the midleg attenuated and often stopped the wingbeat. A miniature remote stimulation device (backpack) mountable on beetles was designed and utilized for the free-flight demonstration. Beetles in free flight were remotely induced into lowering (swing down) each leg pair via electrical stimulation, and they were found to lose significant altitude only when the midlegs were stimulated. Thus, the results of this study revealed that swinging down of the midlegs played a significant role in beetle wingbeat cessation. In the future, our findings on the wingbeat attenuation and cessation mechanism are expected to be helpful in designing bioinspired micro air vehicles.

Insect-machine hybrid robot

Recently, insect-machine hybrid robots have been developed that incorporate insects into robots or incorporate machines into insects. Most previous studies were motivated to use the function of insects for robots, but this technology can also prove to be useful as an experimental tool for neuroethology. We reviewed hybrid robots in terms of the closed-loop between an insect, a robot, and the real environment. The incorporated biological components provided the robot sensory signals that were received by the insects and the adaptive functions of the brain. The incorporated artificial components permitted us to understand the biological system by controlling insect behavior. Hybrid robots thus extend the roles of mobile robot experiments in neuroethology for both model evaluation and brain function analysis.

Research on Key Techniques of Insect Flapping Onset Control Based on Electrical Stimulation

In this paper, an insect flapping onset control method based on electrical stimulation is proposed. The beetle (Allomyrina dithotomus, Coleoptera) is employed for the research carrier, and it’s left and right longitudinal muscles are electrically stimulated to control the flapping onset behavior. The control principle of insect flapping onset utilizing electrical stimulation is analyzed firstly followed by the movement function of the dorsal longitudinal muscle. Subsequently, a micro-control system, which is composed of a PC controller, coordinator and electronic backpack, is designed to realize the wireless control of beetle movements. Finally, the verification experiment is implemented to verify the effectiveness of dorsal longitudinal muscle stimulation with respect to the beetle flapping onset, whereas the comparative experiment emphasizes on determining optimal simulating parameters. The experimental results demonstrate that when the period, duty ratio, number of and amplitude of pulses stimulation signal are assigned to 5 ms, 20%, 90 and 3.3 V respectively, the beetle flapping onset can be controlled with an average response time of 1.69 s. Simultaneously, the optimization of duty ratio from 20% to 40%, and the number of pulses from 90 to 100, is proved to the best parameter configuration.

A review on animal-robot interaction: from bio-hybrid organisms to mixed societies

Living organisms are far superior to state-of-the-art robots as they have evolved a wide number of capabilities that far encompass our most advanced technologies. The merging of biological and artificial world, both physically and cognitively, represents a new trend in robotics that provides promising prospects to revolutionize the paradigms of conventional bio-inspired design as well as biological research. In this review, a comprehensive definition of animal-robot interactive technologies is given. They can be at animal level, by augmenting physical or mental capabilities through an integrated technology, or at group level, in which real animals interact with robotic conspecifics. Furthermore, an overview of the current state of the art and the recent trends in this novel context is provided. Bio-hybrid organisms represent a promising research area allowing us to understand how a biological apparatus (e.g. muscular and/or neural) works, thanks to the interaction with the integrated technologies. Furthermore, by using artificial agents, it is possible to shed light on social behaviours characterizing mixed societies. The robots can be used to manipulate groups of living organisms to understand self-organization and the evolution of cooperative behaviour and communication.

Neurotransmitter-Loaded Nanocapsule Triggers On-Demand Muscle Relaxation in Living Organism

This paper reports the on-demand artificial muscle relaxation using a thermosensitive liposome encapsulating γ-aminobutyric acid (GABA) inhibitory neurotransmitter. Muscle relaxation is not feasible in principle, although muscle contraction can be easily induced by electrical stimulation. Herein, thermosensitive liposomes (phase transition temperature = 40 °C) were synthesized to encapsulate GABA and were injected into a leg of a living beetle. The leg was wrapped around by a Ni-Cr wire heater integrated with a thermocouple to enable the feedback control and to manipulate the leg temperature. The injected leg was temporarily immobilized by heating it up to 45 °C. The leg did not swing even by electrically stimulating the leg muscle. Subsequently, the leg recovered to swing. The result indicates that GABA was released from liposomes and fed to the leg muscle, enabling temporal muscle relaxation.

Insect-Computer Hybrid Robot

An insect–computer hybrid robot, often referred to as a biological machine or an insect cyborg, is the fusion of a living insect platform and artificial microdevices, including stimulators, sensors, and computers. When compared with the artificial robots, a hybrid robot can be operated as an autonomous mobile machine with low energy consumption and hardware costs. A hybrid machine can verify various biological hypotheses, such as function determination, by stimulating a muscle or any other structure.

3D Hybrid Small Scale Devices

Interfacing nano/microscale elements with biological components in 3D contexts opens new possibilities for mimicry, bionics, and augmentation of organismically and anatomically inspired materials. Abiotic nanoscale elements such as plasmonic nanostructures, piezoelectric ribbons, and thin film semiconductor devices interact with electromagnetic fields to facilitate advanced capabilities such as communication at a distance, digital feedback loops, logic, and memory. Biological components such as proteins, polynucleotides, cells, and organs feature complex chemical synthetic networks that can regulate growth, change shape, adapt, and regenerate. Abiotic and biotic components can be integrated in all three dimensions in a well-ordered and programmed manner with high tunability, versatility, and resolution to produce radically new materials and hybrid devices such as sensor fabrics, anatomically mimetic microfluidic modules, artificial tissues, smart prostheses, and bionic devices. In this critical Review, applications of small scale devices in 3D hybrid integration, biomicrofluidics, advanced prostheses, and bionic organs are discussed.

Feedback Control-Based Navigation of a Flying Insect-Machine Hybrid Robot

This study reports the first ever demonstration of the aero navigation of a free-flying insect based on feedback control. Instead of imitating the complicated kinetics and mechanisms of insect locomotion, a live insect can be directly transformed into a soft robot by embedding it with artificial devices. Since many insects can perform acrobatics aerially, thereby exhibiting far greater flexibility than current man-made flyers, correctly commanding the internal structures of an insect to perform based on the instructions would be a breakthrough. Herein, beetles (Mecynorrhina torquata) were chosen as the flying platform, and an inertial measurement unit-implemented electronic backpack was designed and manufactured to remotely command the beetles. To achieve horizontal flight control, multiple flight muscles of the beetles, that is, the basalar and third axillary muscles were stimulated to control the flight directions. However, the beetles were found to gradually adapt to the electrical stimulation, and the flight corrections were elicited by generating compensatory flight forces during a long-lasting stimulation (>300 ms), which were revealed by the decrease in induced lateral force. Based on this finding, a proportional derivative feedback controller was designed to navigate the flying beetles based on the predetermined path using frequency-dependent electrical pulses. To avoid a continuous stimulation, we proposed a stimulation protocol which separated two stimulations with a 50-ms rest. Compared to long stimulations (>300 ms), a 150-ms stimulation with 200-ms update interval was more efficient in correcting the flight direction of the beetles.