• EFR32BG27 Series 2 SoCs

Powering Lura Health’s Tooth-Mounted Salivary Health Monitor


With growth in the smart wearables market, more and more consumers have access to convenient, user-friendly continuous data monitoring devices. However, there’s still potential for this technology in the critical diagnostics space.

The New Blood: Saliva

Saliva, the extracellular fluid secreted by salivary glands in the mouth, can be used to test for a wide range of health conditions, containing potentially over 1,000 biomarkers such as the body’s pH (acidity), glucose levels, electrolyte count, and more. It’s an incredibly data-rich medium. Today, saliva monitoring occurs via one-time measurements at point-of-care facilities; however, since saliva offers evolving insights into a patient’s condition, one-time measurements, even taken regularly, leave out critical information that can only be obtained through continuous monitoring.

To address this gap in preventative care, Lura Health designed the world’s first continual salivary health monitor to improve oral and systemic health and reduce out-of-pocket spending on health care.

The Challenge

To develop a continual salivary health monitor that can be worn inside the mouth to track oral and systemic health.

The Solution

Silicon Labs EFR32BG27 small Bluetooth SoC features an ultra-small WLCSP package with low power consumption, Bluetooth connectivity, and sizable memory for connected medical devices, wearables, sensors, switches, and more.

The Result

The Oral Acid Monitor is a first-of-its-kind design and one of the smallest IoT devices in the world.

Getting Down to Size with our Small Bluetooth Chip

Lura Health’s Oral Acid Monitor includes a sensor worn in the mouth that takes continual saliva readings and transmits data to the patient’s smartphone via a secure Bluetooth connection. The associated smartphone app provides real-time health alerts and clear, intuitive data analysis for patients and doctors alike.

While the device is still in development and not currently approved for sale or distribution in the United States, the team is going to market with a smart retainer design that features a small module embedded in high-quality, transparent plastic. With access to better and better technology, Lura Health is experimenting with two other configurations. One design has the module bonded to a ring that fits around the tooth, and the other design is small enough to be bonded directly to the surface of a tooth. No microcontroller on the market has been small enough to accommodate a tooth-mounted design until the release of Silicon Labs small Bluetooth LE SoC, the BG27.

With an ultra-small WLCSP package ( 2.3 mm x 2.6 mm), Silicon Labs BG27 is small enough for Lura Health to design to the scale of the human mouth, and its power consumption is low enough that the device can last from six months to a year on a battery of the equivalent size. With up to 768 kB of flash program memory and up to 64 kB of RAM data memory, there’s enough space for Lura Health to store sophisticated code that enables a range of device functionality. Real-time data analysis allows patients to gain meaningful information from monitoring, and secure over-the-air (OTA) updates allow patients to always have the most up-to-date software refinements, so adequate memory is a critical feature. Further, the BG27 has all of the peripherals the team needed to interface with sensors and other external hardware component required by Lura Health’s system design.

Lura Health tested other microcontrollers that were comparable to Silicon Labs BG27 in size and power consumption, but they came with substantial limitations in terms of memory and development. Without a convenient integrated development environment (IDE), appropriate documentation, or a community forum, firmware development was an uphill battle.

With Silicon Labs, Lura Health had a direct line to engineering experts, which was critical when identifying non-standard solutions to optimize the bill of materials (BOM). While the reference BOM features an excellent selection, Lura Health needed to meet all design constraints with as few parts as possible. Picking the wrong component meant wasting development time and money. The margin of error was very small, and Silicon Labs helped the team avoid costly mistakes. For example, Lura Health leveraged a Silicon Labs reference design for their custom antenna. Bluetooth antennas present challenges at such a small scale, and Silicon Labs’ offering had the RF performance to transmit the distance between a patient’s mouth and their phone in a small form factor.

Looking Forward – Enabling Innovation in Wireless Oral Health

Silicon Labs BG27 has the hardware specifications, features, size, power consumption, and software environment to reach the specifications Lura Health wants for its Continual Salivary Health Monitor. The availability of this SoC is enabling them to push the boundaries of diagnostic testing with a version of their module that’s small enough to mount on a tooth. Today, Lura Health is working on this design and several other iterations as they seek U.S. Food and Drug Administration (FDA) approval.

The small size and low power consumption of the BG27, coupled with the developer services and design tools Silicon Labs offers, has helped us create the world’s first salivary diagnostic, wearable sensor. The engineers at Silicon Labs are top notch.
Noah Hill
Cofounder and CTO of Lura Health

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