Note: Development of leg size sensors for fluid accumulation monitoring.

A number of diseases can lead to fluid accumulation and swelling in the lower leg. Early detection of leg swelling can be used to effectively predict potential health risks and allows for early intervention from medical providers. Hence this note develops a novel leg size sensor based on the use of magnetic field measurement. An electromagnet is combined with two magnetic field transducers to provide a drift-free leg size estimation technique immune to environmental disturbances. The sensor can measure changes as small as 1 mm in diameter reliably during in vitro tests. Its performance is compared with that of other size measurement techniques.

Magnetic sensor for configurable measurement of tension or elasticity with validation in animal soft tissues.

This paper presents a novel Hall-effect-based magnetic sensor for handheld measurement of either elasticity or tension in soft tissues. A theoretical model is developed for the mechanical interaction of the sensor with the tissue, and conditions are established under which the separate effects of tension or elasticity can be measured. A model of the magnetic field within the sensor is developed and a technique to estimate the sensor response in the presence of multiple magnets is established. This paper then provides analytical sensor responses and compares them with experimental results obtained on synthetic materials. It is found that the sensor can measure tension values upto 100 N with a resolution of 10 N in handheld operation and elasticity of upto 0.87 MPa with a resolution of 0.02 MPa. Significant experimental characterization and statistical analysis of sensor repeatability is performed. The viability of this sensor to make tension and elasticity measurements with biological tissues is then demonstrated using turkey tendons and fresh swine tissues.