Food‐Based Edible Wireless Sensing Device with Isotropic Electromagnetic Response for Gastrointestinal Monitoring

ABSTRACT Small oral‐intake sensors are extremely effective in detecting diseases concerning the digestive system because those sensors enable remote monitoring of information in the body through oral intake. Conventional oral‐intake sensors contain indigestible substances, such as batteries and cameras. Hence, if those sensors become lodged in the narrowed gastrointestinal tract, highly invasive procedures such as laparotomy are required for their removal. To solve this issue, edible digestible sensors with split‐ring resonators (SRRs) have previously been proposed. The proposed digestible sensors use electromagnetic waves for measurement, however, the response of the electromagnetic wave of the digestible SRR sensor is anisotropic, resulting in the limitation of the direction of electromagnetic wave irradiation to the digestible sensor's attitude for acquiring the electromagnetic response. In this study, we propose a food‐based edible monitoring device that responds isotropically to electromagnetic irradiation. The device consists of only ingredients: a cubic sugar substrate with an edible gold thin‐film electrode on an edible starch sheet. The isotropic electromagnetic wave reflection characteristics and digestion properties in in vitro environment mimicking the gastrointestinal tract have been examined.