The mouth offers valuable insights into the condition of the human body. Yet, deploying intraoral sensors to measure oral temperature or jaw movements poses challenges in safety and acceptability. Consequently, real-world data for intraoral research is scarce. To address this gap, we leverage the widespread use of dental retainers and enhance them with Densor: an electronic sensing platform requiring only a standard smartphone for charging and data retrieval using a Near Field Communication interface. Its low power architecture enables prolonged sensing on a single charge, making it suitable for sleep studies. It can provide practitioners with feedback on treatment compliance, and is even able to detect if the user is speaking or drinking water. Densor presents an intraoral, actively powered, battery-free platform featuring multi-modal sensors and an extended lifespan.@en

In recent years, the number of wireless applications has increased significantly, resulting in the radio bands becoming expensive and prone to interference. There is a new research area aiming at mitigating these issues by creating communication links using ambient light. This area, called passive-VLC, not only exploits the visible light frequencies, but does so with low-power transmitters. All the previous work in passive-VLC, however, forget about individual wavelength bands of light, and do not exploit its wide spectrum, reducing the potential channel capacity. In this paper, we propose a novel method to transmit and decode data, using liquid crystal cells that modulate and consider the full spectrum, and put it to the test by prototyping a multi-symbol communication link. The main contribution of our work is to show that passive-VLC can move from spectrum-agnostic to spectrum-aware modulation. We explore this new domain by making use of a novel type of receiver (i.e., a spectrometer) and uncovering the advantages and caveats of this spectrum-aware approach.

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