Robotics tries very hard to match the agility, versatility, and efficiency of animals. Some robots get very close in a few specific ways, but we’re still chasing the dream of robots that can match our biological friends. One way of getting around this problem is by leveraging biology in the design of robots (and we do see a lot of bioinspiration in a variety of applications), but a more direct approach is to just make the robots themselves mostly biological. We’ve reported on this in the past in the context of flying insects, but this new cyborg beetle from Nanyang Technological University in Singapore is the smallest (and most controllable) yet.
Here’s how the Singaporean researchers, led by Professor Hirotaka Sato, describe their work in a recent paper:
It is possible to use a living insect as a platform to develop a living insect-machine hybrid robot. Such a hybrid retains the complex structure of the insect’s rigid exoskeleton, compliant joints, and soft actuators, as well as the insect’s locomotion capability, and it does so while enabling high controllability and low power consumption. Such an insect-machine hybrid robot is made of a living insect platform with a miniaturized electronic device attached on it to control it. By using the insect itself as the robot, researchers bypass the complex processes of designing and fabricating the robot body, using the insect’s muscular system as the soft actuators and flexible joints and its nervous system as part of the control system.
This particular beetle is a type of darkling beetle. It’s small (2 to 2.5 centimeters), lightweight (about 0.5 gram), and lives for three months or so, which is a long time for a little bug. A backpack of electronics interfaces with the beetle’s antennae, and when the antennae are stimulated with an electric pulse, it activates the beetle’s built-in escape mechanism, fooling it into thinking it’s running into something and causing it to turn.
The advantage of doing things this way (as opposed to direct nerve or muscle stimulation, something that the researchers also experimented with) is that the beetle’s brain is still in charge of controlling its limbs such that it’ll respond to high-level controls with adaptive gaits and such, making locomotion a much simpler problem to solve. With just two coin cell batteries, the cybeetle can be controlled for 8 hours, which is long enough for it to travel over a kilometer at an average speed of 4 cm/s.
The key to effectively controlling an insect using these methods is that the response to the antenna stimulation can’t be binary, since you’d end up with a level of control that would often be too coarse to be useful. By changing the frequency of the stimulation, the researchers were able to modulate how sharp of a turn the insect took: Increasing the stimulation frequency also increased the insect’s turning rate, with a success rate of over 85 percent. Stimulating both antennae at once causes the insect to back up, and it moves forward by default, giving you just about as much control as you can hope for.
For more details, we spoke with Tat Thang Vo Doan, first author on a paper on this cybernetic insect appearing in the journal Soft Robotics.
IEEE Spectrum: How are your living robots different from other cybernetic insects that we’ve seen in the past, like cockroaches, dragonflies, and larger beetles?
Tat Thang Vo Doan: Electrical stimulation is commonly used for neuromuscular stimulation in cyborg insects such as cockroaches, giant beetles, and moths. There are other groups working on antenna stimulation but they were not able to grade the response of the insect, which is very important for developing a precise closed-loop control system to make the cyborg insect work autonomously.
Our giant cyborg beetle mainly relies on neuromuscular stimulation of direct flight muscles for flight control and leg muscles of the fore legs for walking control. Ideally, stimulating the muscle would be more precise as we can perfectly control the individual legs, but it costs more in implantation and computing to plan and stimulate all the individual muscles for walking. Antenna stimulation is simpler and easier than stimulating all the individual muscles thus it helps us to simplify the hardware and control system a lot. Hopefully, in the near future, we can control the cyborg beetle as precisely as any other artificial motor.
How does it compare to Draper’s DragonflEye project?
The cyborg dragonfly based on optogenetic for neural stimulation would be the smallest cyborg insect once demonstrated. Although optogenetics is a hot technique, it requires gene modification. At the moment, we are not sure if optogenetics can precisely control the insect locomotion, since not much information was released. However, we hope the cyborg dragonfly works well, and is able to collaborate with other cyborg insects for search and rescue operations in the future.
We believe there’s no perfect cyborg insect. Each of them has its own advantages and disadvantages. It’s better that we can use them all together for a collaborative rescue operation to increase the efficiency as much as possible.
Why did you decide to use this particular kind of insect?
We use Zophobas beetle to develop this cyborg insect because its small size (2-2.5 cm) would help it to access the small rubbles system easily at disaster sites, where the cockroach and giant beetle can not get in. Moreover, a swarming of flying and walking cyborg insects of various sizes would increase the coverage and reduce the searching time, thus enhancing the efficiency and accuracy of search and rescue operations.
Would these insects be able to carry sensors? How would they be controlled in a disaster scenario?
For walking cyborg insects, we are able to integrate external sensors into the backpack as the insect is able to carry loads up to double its weight. We are developing a new backpack with integrated sensors for human detection and navigation. It would help us to detect victims when using cyborg insects at disaster sites, and enable the cyborg insects to work autonomously.
For a disaster scenario, we could release hundreds of flying and crawling cyborg insects to the sites as the price for one cyborg insect would be negligible once mass produced. The insects can move freely themselves into the collapsed structures and send back maps of their positions and environmental conditions so that the rescue team can plan for their action efficiently on how and where they should access. Once an insect detects a victim, it will send an alarm to the rescue team and switch to autonomous control mode to move around the victim for confirmation and build a clearer map of surrounding environment. At the end of the rescue operation, all the insects will autonomously return to the control base. I know that it sounds like science fiction, but we are in fact working to realize it.
When do you think living robots like these will be useful for practical real-world applications?
Based on the current progress of cyborg insects, I think that we will be able to use cyborg insects for some real applications within 5 years. Of course, I don’t mean search and rescue missions, as we would need much more time for that.
What are you working on next?
We are now working on a feedback control system to precisely control the insect locomotion with high reliability. We are also developing a new backpack with a navigation system and environmental sensors designed to promote fully autonomous and practical cyborg insects.
For real applications, we need to maintain the power supply for the cyborg insect (mainly for the electronics backpack), which is currently a huge challenge if we just rely on the battery. So we are developing a biofuel cell, which is able to convert biofuel inside the insect to electric current for running the control backpack. It will help to maintain the backpack power for long-term use.