A health monitoring Swiss Army knife
Most research tools for collecting health data are expensive, inflexible, and a black box in terms of data processing. ExtHub attempts to buck these trends.
extHub
A configurable platform that enables a wide breadth of exploratory health sensing research.
Tasked with developing a wearable device to both monitor circadian rhythm and control dosing from a biolectronic implant, we developed the External Hub to excel at these tasks. We also spotted a need in the research community for high-quality, flexible, and wearable health sensing solutions that give access to raw data. We used this research as an opportunity to create a suite of devices that sense a wide variety of physiological parameters like ECG, multi-wavelength photoplethysmography, ballistocardiography, skin temperature, and activity.
Circuit Design
The base module hosts a Bluetooth Low-Energy capable microcontroller, battery management, options for user input and notification, and a wide variety of sensors.
The module can interface with any of a number of power-up modules like the ECG and PPG modules shown here. This flexibility allows the same device to be used in a variety of locations on the body and harvest targeted, complementary information from each site.
Enclosure Design
The device enclosures are 3D printed in a high precision SLA resin. They are easily assembled and disassembled to enable rapid iteration, yet still are waterproof and rugged enough to allow for “in-the-wild” user testing.
Unique lids are designed to interface with each power-up module, allowing the devices to perform their intended health sensing tasks on the body.
Mobile Application
When developing methods for novel health metrics, it's crucial to have access to raw sensor data with accurate timestamps to create new algorithms. Alongside extHub, we developed a mobile application that allows real-time sensor data visualizations and the ability to update embedded variables in real time using BLE. This app extends the flexibility of the extHub hardware, enabling rapid prototyping and experimentation for any application built with extHub.
The application dynamically stores data in a relational model indexed by timestamp and keeps track of embedded settings for reproducibility. We utilized this app to explore multiwavelength PPG by exposing settings for the number and brightness of LEDs and the gain of the photodiode.
Wearable Integration
To enable extHub to collect real time health data from multiple locations on the body we designed a versatile textile harnessing method. Velcro straps are integrated into various wearable form factors, and these straps wrap around plastic loops in either side of the enclosure in order to secure it in place while still allowing the device to have direct skin contact.
New Hardware Leads To New Insights
Embedded in our work is the strong belief that progress is enabled by access to the right tools. The extHub ecosystem allows the Hester Lab to study physiological signals in contexts that weren’t previously possible. Explore the heart rate data in the graph to the right, collected wirelessly and simultaneously from two extHub devices collecting ECG and PPG signals, respectively.