Temperature Regulation and Automatic Saliva Delivery System for a Biomimetic Oral Cavity

Analyzing the food texture during mastication is extremely important for the development of ingestible products. Chewing robots allow for an objective and repeatable in vitro assessment of the food texture and properties. The University of Auckland has developed a chewing robot that can mimic the movement of the molars during mastication and allows controllable molar grinding kinematics as well as a food repositioning function. The robot’s biomimetic oral cavity, however, lacks a salivary gland that releases saliva when needed, thus the existing cavity cannot accurately mimic the human oral processing. This thesis’ aim is to develop an improved version of the oral cavity that allows for saliva circulation during chewing and saliva temperature control to be integrated with the existing chewing robot. Moreover, since currently the University of Auckland is using the robot to run mastication simulations on pharmaceutical drug products, the extracting and storing method of saliva needs to be able to guarantee uniform dispersion of the drug in the saliva. To achieve this, the design of the oral cavity itself has been modified to accommodate the injection and extraction of saliva during chewing without losing the food repositioning function and compatibility with the existing chewing robot. In addition to the design modification, an automatic saliva delivery system which allows for closed loop control of the saliva flow rate into the oral cavity as well as a temperature control system has been developed. The automatic saliva delivery system has been realized through the use of a peristaltic pump and a liquid flow sensor, which combined with a PI controller allows for closed loop flow rate control. The temperature control of saliva has been implemented in a separated insulated chamber from which the saliva is extracted to be delivered to the oral cavity. Inside this container a heating pad controlled with a Bang-bang controller allows to keep the temperature around the desired value. Finally, a simple GUI has been realized in order to be able to change the desired flow rate while the system is running without needing to restart the test.