Open Sesame: A Jewelry Replacement For Subway Farecards

The Sesame Ring is a 3-D printed RFID ring that lets users pay their subway fare with a finger’s flick.

Two students with a passion for jewelry and hacking did the impossible: They built a ring that doubles as a subway farecard and got legal clearance to use it on the Boston T.


Edward Tiong and Olivia Seow’s 3-D printed Sesame Ring features an embedded RFID chip compatible with the Boston MBTA’s CharlieCard (a rechargeable farecard similar to existing ones on the Washington D.C. Metro, the New York/New Jersey PATH, and the San Francisco/Oakland BART). Instead of fishing a farecard out of a wallet, pocket, or bag, a user simply swipes their ring at a turnstile and refills it either online or at a vending machine. The pair are students at the Singapore University of Technology and Design who developed the MBTA ring as exchange students at MIT.

Tiong and Seow’s company, The Ring Theory, recently raised $19,000 (well over the designers’ initial $5,000 goal) on Kickstarter, offering customizable rings for $17 each. Ring Theory’s initial design, shown above, is likened by the creators to a “wearable CharlieCard.”

In a phone conversation, Seow and Tiong noted that the ring is fully compatible with the CharlieCard and relies entirely on a CharlieCard chip embedded within the jewelry. Similar attempts have been made before to create wearable NFC or RFID devices such as smart rings for NFC-enabled door locks and even Walt Disney World’s RFID wristbands, but this is the first time the concept has been applied to public transportation. Because the rings use standard-issue RFID chips, they can be easily tweaked for other public transit systems (and even, hypothetically, other RFID-enabled payment systems.

After working on a pilot in Singapore giving students RFID jewelry to open doors at libraries and laboratories, Seow and Tiong decided to adopt the concept to American public transportation. The MBTA gave their blessing to the experiment, and after a brief discussion over whether to 3-D print the physical rings or use a more conventional manufacture method like mold injection, they were off. Tiong told me that, for their needs, 3-D printing was the most cost-effective and easy method of manufacture.

In order to add money to their transit ring, users simply press their accessory to an MBTA vending machine, which adds rides as if it were a normal farecard. Tiong says in promotional materials: “We are not inventing anything new or cutting edge. We are looking at the most common technology that has been around for a long time, and saying, hey maybe we can do something different with this.”

Correction: An earlier version of this article misdentified Seow and Tiong as MIT students. They are students at the Singapore University of Technology and Design attending MIT on an exchange program.