Final Design

The final design of SomnoStay contains 3 critical components, detailed below. The suction device applies light negative pressure directly onto the surface of the tongue to keep the tongue located at the roof of the mouth. A pressure system is used to monitor suction pressure levels and controls a small air pump through an Arduino UNO and MOSFET. Finally, a buffer volume was designed to prevent saliva from leaving the mouth and entering the pressure sensors. Details of each component are listed below.

Suction Device

CAD Model of Suction Device

Suction Device Prototype

CAD Models of our final suction device, as well as the physical prototype are shown in the figures. The retainer was inspired by the Hawley Retainer and was selected as the final design choice. The design optimizes the level of comfortability for the wearer and spreads an even level of suction throughout the tongue. To fabricate the retainer, a high resolution 3D Printer was needed due to the unique and customized nature of the design. The Connex3 Photopolymer 3D Printer was used to fabricate prototypes of the device, using a mix of VeroClear and AgluisBlack 30 filament. The inner supports are water soluble, so they device was soaked in water to create an air cavity within the retainer, ideal for creating suction. The printer also has the ability to print biocompatible material, and while current prototypes are not biocompatible, mass produced product would be.

Pressure Controller

In order to regulate the suction applied through the retainer to the tongue, a feedback loop was hardwired using the above wiring setup. The Arduino Uno, in combination with a laptop, was running a program using the Arduino IDE to regulate the motor speed. The program takes the pressure sensor signal, represented as the yellow wire in the wiring diagram, which is read by the Arduino IDE. The program then increases the motor speed if the pressure is less than desired, and turns off the motor if the pressure is more than desired. This change is communicated physically through the blue wire to the MOSFET, which regulates the voltage difference between the two terminals of the motor pump. The pump then speeds up or shuts off accordingly, which alters the pressure in the tubing system. This new pressure is read one second later by the pressure sensor, and the loop repeats itself.

Internal Wiring

Buffer Volume

Tea bag filter

The choice of a modified airtight container was to limit the amount of air leakage when the motor was turned on. The modified part of the container are two drilled holes to allow the connection from the suction device to the rest of the system. At these two holes are tubing mounts to limit the amount of air leakage.General knowledge suggests modifying an airtight container is best instead of creating an airtight container because there is a lower chance of air leakage. The size was also something to analyze but I think the smaller the better so that it is more portable compared to typical OSA treatments.

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