Pectus excavatum is a congenital birth defect which manifests as a 'sunken chest' appearance. Traditional surgical methods to correct for this deformity are invasive and painful. Dr. Harrison of UCSF has developed a less invasive and less painful method that corrects the deformity over time using a gradual application of magnetic fields and forces.

Currently a device (the Magnetic Mini-Mover) is in FDA clinical trial. An on-board datalogger was required to verify functionality and patient compliance. An ultra-low power datalogging system (consuming sub-microamp sleep current) was designed and implemented to record magnetic force (for verifying treatment) and temperature (for verifying compliance). Data is saved to an on-board micro SD card. PC software was developed in conjuction for the operator to quickly download and analyze data in an office setting.


An active area of orthopedic and biomechanic research is studying the effect of mechanical loading on the biochemistry and long-term health of joints. It is known that osteoarthritis can result from trauma to joint tissue, either in small quantities over time or in large, sudden injuries. Measuring and quantifying the loading on people's knees, and tracking their knee health over time, is important to developing preventative measures against arthritis.

A datalogging system to monitor cartilage vibration amplitude and frequency was designed and tested on adult knee joints. Data is saved to an on-board micro SD card, and downloaded and analyzed using MATLAB. A highly sensitive vibration sensor was used to capture large amplitude and high frequency accelerations. The sensor was mounted directly on the knee, and the datalogger strapped to the leg, and worn by active healthy adolescents for a period of one week.

Due to its high performance the sensor module consumes a lot of energy, so a sleep-and-threshold detection system was implemented to save on battery life while capturing relevant data. Future versions will use a lower energy accelerometer that focuses on a lower frequency and specific amplitude range.