By Josh Perry, Editor
According to a recent report by 3DPrint.com, graduate students at Santa Clara University (Santa Clara, Calif.) have designed a wearable, thermoelectric biosensor that uses ambient air, body heat, and heat sinks in a 3-D printed package.
A prototype of the wearable medical device produced by the students.
(Santa Clara University)
The initial prototype is a wristband with a thermoelectric module that produces low voltage electricity. A boost converter increases the voltage to a level that is usable for medical devices.
According to a paper, “Powering a Biosensor Using Wearable Thermoelectric Technology,” released by the students, “Our goal was to use this generated power to charge medical device batteries off-the-grid, increasing medical device user freedom and allowing medical device access to those without electricity. We successfully constructed a wearable prototype that generates the voltage required by an electrocardiogram battery; however, further thermoelectric module and heat dissipation optimization is necessary to generate sufficient current to charge the battery.”
The students indicated that the design of the heat sink was of primary importance because it needed to dissipate the correct amount of heat, remain low-profile, and fit into the system package.
“Fin and pin type heat sinks were identified as the ideal geometries for our application,” the paper explained. “Heat sinks are often used in conjunction with fans for forced convection; however, our application relies on still air and natural convection, and adequate space between fins or pins is needed to allow free air to flow between them.”
3-D printing was chosen as a method for constructing the prototype housing because it reduced time between iterations and the material was rugged enough to withstand impact while protecting the components. The plastic also acts as an electrical insulator for the thermoelectric module leads.
“We came to the conclusion that directly installing heat sinks and thermoelectric modules into the wristband prototype without some sort of housing was very dangerous for the small and fragile TEMs, produced inconsistent heat sink efficiency due to inconsistent contact with TEMs, and exposed the thermal circuit to potential interference,” the paper continued.
It concluded, “The housing for our heat sink and thermoelectric module assemblies is the most patentable concept found in our project. In order to patent this housing we would need to isolate the unique design features for the housing. Specifically, the ridges used to hold the heat sink and the body shape of the housing which protects and fastens the assembly in place while allowing for serial and parallel configurations.”