RIKEN announced on September 5, 2022 that a joint research team from RIKEN, Graduate School of Creative Science and Engineering, Waseda University, and Nanyang Technological University in Singapore has developed a cyborg insect that can be recharged with light energy.

A cyborg insect equipped with a small IC can operate for a long time in an environment inaccessible to humans. It is expected to be used for applications such as urban search and rescue, environmental monitoring, and inspection of dangerous areas.

In order to remotely control the movement of cyborg insects for a long time and acquire environmental data, an energy harvesting device such as a solar battery that can supply 10mW or more is required. On the other hand, if a large solar cell is used, the size and weight of the insect impair the motility of the insect. Therefore, there has been a demand for a method of supplying an output of 10 mW or more while maintaining the insect's motility.

In this study, an electronic device was mounted on the back of a Madagascar cockroach about 6 cm long. A wireless mobile control module and a lithium polymer battery were attached along the curved surface of the dorsal side of the thorax of the insect using a soft backpack, and a thin organic solar cell module with a thickness of 4 μm was attached to the dorsal side of the abdomen.




A backpack was designed based on a 3D model of a Madagascar cockroach, and an elastic polymer was made by 3D printing. The surface of the backpack that comes into contact with insects has a columnar structure that matches the curved shape of the back of the chest.

As a result, they perfectly fit curved surfaces without being affected by differences in the shape of individual insects, making it possible to stably mount hard electronic devices. This adhesion was maintained after 1 month in the breeding environment.

A thin organic solar cell fabricated on a polymer film was attached to the dorsal side of the abdomen of an insect with a ``stepping stone structure'' in which adhesive regions and non-adhesive regions were alternately arranged. It ensures freedom of movement of the abdomen.








The effectiveness of this method was quantified by the time required to traverse an obstacle. The median time is 2.4 seconds when no film is attached to the abdomen of the insect, and 2.2 seconds when a film with a thickness of 3 μm is adhered to the stepping stone structure. On the other hand, when the thick film was used, the median time was 4.2 seconds, which was a long time.





getting up test



In addition, when we confirmed the ability of insects to stand upside down on the ground, the success rate of insects without the film was 99%. Successful rising rates for 10 μm films were 96% and 81%, respectively. On the other hand, when a thin organic solar cell module with a thickness of 4 μm was attached, the rising success rate was 100%.

On the other hand, films with a thickness of 15 μm and 20 μm were 46% and 16%, respectively. In addition, when a 2 μm-thick film was adhered to the abdomen without the stepping stone structure, the success rate of getting up decreased to 10%.


Thin organic solar cell module for cyborg insects



Finally, we validated charging and wireless locomotion control using live cyborg insects. After fully discharging the battery, simulated sunlight was applied to the organic solar cell module of the cyborg insect for 30 minutes.

Using power from a charged battery, the cyborg insect wirelessly received a signal to control the on/off of stimulation, and the stimulation signal was input to the stimulation electrode connected to the insect tail lobe for about 2 minutes. We tried to control the movement to the right several times, and confirmed that radio control was possible.




Wireless behavioral control of rechargeable cyborg insects



The method can also be applied to insect species other than Madagascar cockroaches. In the future, we plan to further expand the functions of the cyborg insect by making the control circuit thinner and combining it with other components such as sensors.