RoboFood is an innovative concept within soft robotics, wherein electronic products are manufactured from edible, biodegradable materials.
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What is RoboFood?
An extreme quantity of electronic waste is generated every year that is unsuitable for, or otherwise not recycled, and eventually makes its way to landfill. Biodegradable electronics are one potential solution to the electronic waste burden and offer numerous novel applications. For example, medicines could be delivered to wild animals via edible drones; swallowing could be facilitated mechanically for patients who struggle with eating, or life-saving nutrition delivered in emergencies, all while simultaneously monitoring environmental conditions such as temperature and humidity that affect cargo quality.
The Robofood project is currently headed by the Laboratory of Intelligent Systems, at the Swiss Federal Institute of Technology Lausanne. It is an internationally collaborative effort receiving funding from the European Union’s 2020 Research and Innovation program. The aim of the project is to combine traditional inorganic robots, able to interpret and interact with their environment in fulfillment of some function, with organic material able to be metabolized by living creatures, using soft robotics and advanced food processing methods.
Case Study: Edible Sensors
RoboFood recently produced an edible bistable tilt sensor, able to detect the orientation of a robot based on a commercially available inedible example. This is the first edible robot that can detect its own body orientation, opening up numerous locomotive applications for edible robots.
It is constructed entirely from materials approved by the European Food Safety Authority, largely ethyl cellulose for the non-conductive components and gold for the conductive component. The role of resistors and other electronic components is facilitated by activated carbon, beeswax, sunflower oil, and gummy bears, and the whole system is encased in gelatin for structural integrity and protection. While not the entirety of this prototype is edible, only around 36%, this small contribution accounts for 807.58 kcal, around a third of an adult’s daily calorie requirement.
Case Study: Edible Batteries
An edible battery also developed by the group, named GelBat, was used within the robot, and provided a detectable output even after 259 days in storage. GelBat is constructed from gelatin and activated carbon, and can produce a consistent over 1 V output for around 10 minutes via water splitting reaction.
Specifically, the device is created by setting gelatin containing charcoal powder into two electrodes at low temperature, and subsequently connecting them by setting the electrodes into a conductive gelatin patch.
A potential difference of at least 1.23 V is then applied across the electrodes, sufficient to engage with the redox reaction of water, causing absorbed oxygen to appear at one electrode, and hydrogen at the other. Oxygen and hydrogen gas absorbed to the carbon gel surface can spontaneously recombine, completing the circuit and generating voltage as long as water is available.
The device is charged using a 120 Ω resistor from a 5 V power source for around 10 minutes, then discharges via 1 MΩ resistor for around another 10 minutes. Increasing the concentration of active carbon from 1:50 to 1:10 (mass compared to the volume of gelatin) causes the battery to discharge more slowly. It thereby allows a higher voltage to be maintained for a longer period as the charge dissipates. Similarly, exchanging the 1 MΩ resistor for one of lower impedance causes quicker discharge.
Importantly, GelBat can be recharged over 80 times without any indication of loss of efficiency and can be completely digested within a simulated gastric environment in only 20 minutes. As the only byproduct of GelBat’s operation is water - no toxic by-products are produced, as in conventional batteries. Furthermore, multiple GelBat components can be linked together to generate higher voltages where required.
Case Study: Edible Rescue Drones
Drone technology has allowed a wide variety of unmanned transport operations and has found particular use in the emergency delivery of life-saving nutrition and medicines. However, most conventional small drones are only able to carry around 10-30% of their mass as cargo, severely limiting the quantity of food able to be delivered in one trip.
As briefly discussed, one possible method of improving the nutritional cargo of emergency drones is to construct specific components, or the whole drone, from edible materials. In one example published by Kwak et al. (2022), replacing only the wings with edible materials brings up the mass of food carried by a drone to 50% of total, providing a compact package containing 300 kcal and 80 g of water.
In this case, the wings were constructed from rice cakes, bound to a light metal fuselage featuring a plastic propeller and lithium-ion battery. Rice cakes have a density similar to that of polymer foams such as expanded polypropylene, and lower than other food-safe materials such as gelatin, with good caloric density.
Such a light but calorically dense material is ideal in replacing specific structural components of small drone aircraft, though may not perform well even in only mildly poor weather conditions. Rice cakes also have a relatively high Young’s modulus, or stiffness, and thus maintain good rigidity when dry, and can be easily formed into a suitable wing by laser cutting.
The group investigated edible adhesives containing either gelatin, chocolate, or corn starch to attach the rice cake wing to the drone's body, with the former showing the best resistance to adhesive stress.
Electronics constructed from biodegradable materials are set to significantly lessen the quantity of electronic waste generated by unavoidably disposable products, and in many cases, ensuring that these materials are also food safe provides simultaneous applications. The field of edible robotics is still in its infancy, and at the stage of producing viable electronic components from food-safe materials for specific applications.
In the future, numerous electronic products may be constructed partly or wholly from biodegradable and edible materials, imparting a shorter lifecycle to the product and severely reducing the quantity of waste produced during the product’s life. Specific applications that call for biodegradation are also facilitated by RoboFood, such as an implanted biosensor only intended to remain active for the lifetime of disease treatment and naturally degrade in the bloodstream.
References and Further Reading
Annese, V. F., Kwak, B., Coco, G., Galli, V., Ilic, I. K., Cataldi, P., Floreano, D., & Caironi, M.. (2023). An Edible Bistable Tilt Sensor Enabling Autonomous Operation of a Partially Eatable Rolling Robot. Advanced Sensor Research. doi.org/10.1002/adsr.202300092
Chen, H-Y. , Keller, A. G., Conn, A. T., & Rossiter, J. M. (Accepted/In press). GelBat: An Edible Gelatin-Based Battery. In 2023 IEEE 6th International Conference on Soft Robotics (RoboSoft) Institute of Electrical and Electronics Engineers (IEEE). Available at: https://www.robofood.org/wp-content/uploads/2023/04/GelBat-An-Edible-Gelatin-Based-Battery.pdf
Kwak, B., Shintake, J., Zhang, L., & Floreano, D.. (2022). Towards edible drones for rescue missions: design and flight of nutritional wings. Institute of Electrical and Electronics Engineers (IEEE). doi.org/10.1109/iros47612.2022.9981956