Low-Frequency High Precision Dielectric Sensor for Non-Contact

Physiologic Assessment

John Selker

Dept of Biological and Ecological Engineering

Concept

• People want to know their progress in achieving health goals, including loss of fat and increase in muscle (BMI)

• Getting rid of fat and gaining muscle can give no net change in weight

• Fat has a dielectric (controls capacitance) about 1/100 that of muscle

• Cheap ultra-accurate capacitance sensor– $4 for 2-pair differential capacitance with

1:16,000,000 resolution

Literature supports the efficacy, but at high frequency (expensive!)

• Validation of a new dielectric device to assess changes of tissue water in skin and subcutaneous fat, J Nuutinen et al 2004 Physiol. Meas. 25 447-454   doi: 10.1088/0967-3334/25/2/004     

• Abstract. Easily applicable and inexpensive water-specific techniques to evaluate local oedema, swollen tissue problems and fluid retention in humans are not available. In the present investigation a recently constructed non-invasive device for a local measurement of changes in tissue water in human skin and subcutaneous fat (SSF) was validated. The instrument transmits an ultra high-frequency electromagnetic (EM) wave of 300 MHz

• A Noninvasive Method for Determining Dielectric Properties of Layered Tissues on Human Back Yan, L.P.; Huang, K.M.; Liu, C.J.Journal of Electromagnetic Waves and Applications, Volume 21, Number 13, 2007 , pp. 1829-1843(15)

• Abstract:• A 3-dimensional (3D) reconstruction method based on layered-homogenous-tissue model to

obtain dielectric properties of superficial tissues of human body by noninvasive measurement is presented in this paper. First a circle patch probe fed by coaxial line is optimized by using micro genetic algorithm (MGA) to measure reflection coefficient at a wide frequency range from 1 GHz to 7 GHz. Then reconstruction method based on MGA is discussed and verified by some experiments. Finally, the dielectric properties of skin, fat and muscle, as well as thickness of skin and fat, on the human back are reconstructed. The reconstructed results agree to the published data.

We know the physical properties

At 32 kHzεfat= 450

At 32 kHzεmuscle= 35,000

Business Issues1. Product demonstration. We are working on this and

should have a prototype running in two months• Have PhD electrical Eng on staff on project• Could have sooner if needed

2. Required development steps.• Compare to other known methods

• Make relationship with hospital or other practice

• Publish results• Develop patent• Identify partner company

• Write NDA

3. Write Business Plan.

Competing Devices

• $30-40

•

• $10