Electromagnetic Field Detector Bracelet Cati Vaucelle, Hiroshi Ishii and Joseph A. Paradiso Massachusetts Institute of Technology MIT Media Lab 20 Ames Street Cambridge MA 02139 {cati, ishii, joep}@media.mit.edu ABSTRACT In this paper we present the design of a cost-effective wearable sensor to detect and indicate the strength and other characteristics of the electric field emanating from a laptop display. Our bracelet can provide an immediate awareness of electric fields radiated from an object used frequently. Our technology thus supports awareness of ambient background emanation beyond human perception. We discuss how detection of such radiation might help to “fingerprint” devices and aid in applications that require determination of indoor location. Author Keywords Wearable sensor, ambient signals, capacitive sensor, EMF. ACM Classification Keywords H5.m. Information interfaces and presentation (e.g., HCI): Miscellaneous. INTRODUCTION Before medical technology, people feared what was inside of the body and because of their ignorance attributed diseases such as epilepsy to divine interventions [17]. Now that medical technology exists, people know what the body is made of, and by knowing and visualizing it, they may be relieved from their fear of the unknown. Inside the living body” by Stephen Marsh is a movie that shows how the body transforms as it ages. Its goal is to relieve people from body anxiety as they gain control of what was not perceptively accessible. Today, many people fear electromagnetic fields. They believe (most probably exaggeratedly) that ambient fields can negatively influence their health. Perhaps, by visualizing the presence of common electromagnetic (EM) fields, users might feel in control of difficult-to-perceive information and transcend their fear, beginning the process of recognizing and moving beyond fear. An analogy might be found in the cheap RF power meters that are sold to enable people to gauge radiation leakage from their microwave ovens. Conversely, providing users with blind data could increase their paranoia when low-level field leakage from common appliances is visualized. Clearly, people need to be educated in how to properly interpret this data. Regardless of one’s belief on the health impact of background EM fields, visualizing the unseen in this way always leads to fascinating and playful exploration. All devices emit background signals (electrostatically, magnetically, acoustically, and optically) that are characteristic of particular devices and also sometimes indicate that device’s mode of operation. Indeed, government contracts mandate that computers and displays used in highly classified work be kept in shielded rooms (SCIFs) to thwart espionage that monitors such background leakage fields. In this paper we present a cost-effective implementation of a wearable sensor to detect and display the strength and other characteristics of ambient electromagnetic fields. One implementation pursued in our work is the detection of the capacitively-coupled electric field emanating from a laptop display. To our knowledge, nobody has successfully designed a wearable device that detects and characterizes frequencies radiated from devices like laptop LCD screens, for example, or other appliances around us. Embedding our device into a bracelet offers an immediate awareness of the electromagnetic fields that surround us and are beyond human perception, enabling an extra sense similar to that possessed by electric fish [2]. We are researching the exploitation of such common background signals, such as near-field EM emission, optical modulation, and other invisible or intrinsic characteristics of the local environment in general to assist localization in smart systems. RELATED WORK The public at large has long been concerned that exposure to radio frequency and generic electromagnetic sources are the cause of adverse health effects. Physicists Robert K. Adair [1] and Bob Park [16] explain that weak environmental fields at frequencies ranging from electrostatics through microwave cannot affect biology on the cell level, as the corresponding photons don’t have enough energy to break a molecular bond. Only large electric fields have consequences that can lead to immediate injury or death, e.g. by electrocution or heating (and magnetic fields have even less effect). Although the public