The recent advances achieved in the field of electronics have had important repercussions on the integration between machines and organisms. In particular, the reference is to Cyborgs , more precisely the cyborg insects, increasingly proposed for operations such as search and rescue in the urban environment. To this end, body-mounted energy harvesting devices are critical to expanding the range of activities and functionalities required.
To achieve this, a group of Asian scientists led by the Japanese Riken Institute developed a half-cockroach, half-robot cyborg. With the practicality of being powered by solar energy and remotely controlled without wires .
The reason for solar cells to power cyborg insects
New technological components, capable of integrating with organisms, have increased the demand for higher power supply devices. Battery volume and weight limits for remotely controlled robots can be overcome by using charging strategies.
Alternatively, an energy harvesting device mounted on the robot can extend its range of activity . A promising example are biofuel cells that generate energy from the insect body itself. To date, the highest output power value achieved with enzymatic biofuel cells is 333 µW.
But this value is not enough for advanced functions, such as wireless locomotion control, which require values of several milliwatts or more. A solar cell can generate a power of 10 mW on cm 2 in outdoor sunlight conditions; the highest value thanks to this technology in outdoor conditions.
However, achieving these results involves adopting large-scale solar cell design and integration strategies. Because insects must maintain their basic behavioral skills while receiving the power to operate. Thanks to a module consisting of an ultrasoft solar cell, the researchers created cyborg insects with no impediments to movement skills .
The combination of ultra-thin electronic films with an adhesive and non-adhesive interconnection structure on the abdomen of the insect, allowed the insect to self-right itself. All with a success rate of more than 80% in the various attempts carried out and with an output power of 17.2 mW provided by the solar cell .
Structure and movement of the cyborg insect
Scientists used the Madagascar hissing cockroach for this study, mounting the electronic components on the insect's dorsal part. Thanks to a backpack, specially printed in 3D in order to adapt to the curves of the chest , battery and circuits have found a place on the insect. The abdominal part, on the other hand, is touched by the 4 µm thick solar organic cell.
To control the cyborg insect, the researchers connected the wireless motion control module on the chest to the cerci (Figure 1b). The latter are even appendages on the posterior segments of the abdomen. Once an electrical stimulus is applied to a specific appendage, the insect turns in the right direction. It is an external server that sends motion control signals via Bluetooth wireless technology.
The movement of Cyborg Insects with the ultra-thin film
Sectional observation of the abdomen revealed that each segment of the abdomen partially overlaps during its deformation. The stroke of each segment is up to 2.5 mm. As a solution, the researchers used the combined technology of ultra-thin polymer films and an adhesive and non-adhesive interconnect structure . All this allowing the abdomen to flex (fig 2a).
The film has a hollow structure that selectively adheres only to the non-overlapping part. This adhesive-non-adhesive interconnection structure allows room for the film to fold upward as the abdomen segment moves (Figure 2a).
The effectiveness of the thin film fixation strategy was quantified in two ways. In the first, measuring the time it takes to cross an obstacle, with excellent results once the 3 µm film has been applied. In the second, the tools measured the success rate of “self-adjusting” from an inverted (on the ground) position of the insect (Figure 2e, f). In this experiment, thin films with varying thickness and modulus of elasticity gave different results. But above all, the results confirmed the combination of sufficiently thin films with the interconnection structure as optimal. (100% success with the 4 µm solar cell) .
Possible future developments
The team of researchers , led by Kenjiro Fukuda, has the next goal of integrating sensors and cameras. There is also the will to extend the use of Cyborgs in monitoring and rescue applications for other insects as well. As he stated in fact:
(…) Since abdominal deformation is not unique to cockroaches, our strategy can also be adapted to other insects such as beetles and perhaps even flying insects such as cicadas.
The article Cyborg insects, powered by ultrasoft organic solar cells was written on: Tech CuE | Close-up Engineering .