Eat, Test, Digest: Towards Diagnostic Food for Next-Generation Gastrointestinal Tract Monitoring

Abstract

The development of edible electronics and robotics represents a novel opportunity in several application scenarios, from food monitoring and healthcare to search and rescue. In this context, the EU-funded ROBOFOOD project aims to merge food science, robotics, and engineering to study the possible application of food-derived materials in traditional electronic and robotic components. Besides the possible out-of-body applications, the use of food-derived materials holds great potential for gastrointestinal (GI) monitoring. Avoiding the use of toxic materials, digestible sensorsi.e. diagnostic food -can reduce the risk of poisoning and retention in case of device malfunctioning, limiting the need for surgical extractions.Here we present an edible pressure-induced contact-resistance pressure sensor made of a gelatin-based body, an activated carbon conductive coating, printed gold electrodes and an ethyl cellulose substrate. Preliminary results show that the sensor is successful in detecting pressure changes above a certain threshold depending on the diaphragm height. For a device with a height of 500 µm, the pressure threshold was between 20.3 and 25.3 g/cm 2 . While further developments are required to enable the use of the sensor in real-case scenarios, this work represents a first proof-of-concept of diagnostic food.

A Sprayable Electrically Conductive Edible Coating for Piezoresistive Strain Sensing

“…[18] Identifying edible materials with electronic properties compatible with industrial processing methods and suitable for implementing edible sensors remains an open challenge. [9] Among the edible sensors so far demonstrated, [9,[11][12][13][18][19][20][21][22][23][24][25] a large interest has been shown for strain sensors, [19−23] as they are widely adopted in robotics for the ability to provide feedback from actuators. [21] Piezoresistivity (resistance variation due to a mechanical deformation) has been exploited to produce edible hydrogel-based strain sensors [19,[20][21][22]26] with gauge factor in the range of 0.308 [19] −1.49.…”

“…Finally, at the end of their lifetime, edible devices can be disposed of or repurposed in the same way as food waste. [ 9,10 ] These peculiar properties open previously unconceived scenarios: in agrifood, edible sensors can be applied in direct contact with food for quality monitoring, [ 11 ] for instance tracking fruit growth using strain sensors; [ 12 ] in healthcare, miniaturized edible systems can be engineered to acquire diagnostically relevant information for gastrointestinal (GI) tract monitoring before being metabolized by the body, eliminating the risks associated with retention of ingestible technologies; [ 13 − 16 ] edible robots, equipped with a range of sensors, could also deliver nutrition to humans in an emergency, [ 11,17 ] or act as drug‐loaded prey for wild animals. [ 18 ]…”

“…[ 24,39 − 44 ] AC has been used in combination with polydimethylsiloxane (PDMS), [ 39,40 ] concrete, [ 42 ] foams, [ 43 ] and hydrogels [ 45 ] to produce strain sensors for wearable and structural health monitoring applications. Also, a large variety of edible electronics components leveraging AC have been already implemented (e.g., electrochemical sensors, [ 46 ] supercapacitors, [ 47 ] batteries, [ 34,35 ] tilt sensors, [ 18 ] triboelectric generators, [ 41 ] electrodes, [ 24 ] pressure sensors [ 13 ] ). However, a food‐based strain sensor employing AC as the electronic conductor suitable to be operated in a direct current regime and therefore compatible with edible batteries [ 34,35 ] has not been documented yet.…”

Edible Electronics and Robofood: A Move Towards Sensors for Edible Robots and Robotic Food

“…RC and RLC filters have been fabricated using either activated carbon and egg white [21] or carbonized cotton, starch, and gold [17]. Other remarkable edible implementations include memristors (using casein or garlic) [22,23], battery [24], and supercapacitor [25]. Edible sensors are also gradually emerging.…”

“…A piezoelectric sensor using a film of broccoli powder and gelatin capable of detecting low frequency sound has also been shown [17]. Pressure sensing usingfor instancea gelatin/glycerol hydrogel has also been demonstrated [25].…”