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Neuropathy Diagnostic Device

MAE 156B Spring 2018 Senior Capstone Design Project

Project Background: 

Diabetic neuropathy is a disease in the peripheral nervous system. It afflicts over half of the 415 million diabetic patients worldwide. This nerve disease can lead to the loss of protective sensation and limb amputation. There is currently no FDA-approved treatment for diabetic neuropathy, but biotech company WinSanTor is investigating a proprietary first-in-class therapy to prevent and reverse nerve damage. Current test beds for treatment and detection of neuropathy exist for laboratory animals but human testing is desired.

The current test apparatus ["Thermal box"] is a under-glass heat stimulus based on the Hargreaves' method. A light bulb is used as a heat source to increase the temperature of the glass on the paw of the rat. The reaction time of paw withdrawal due to pain is recorded, and the temperature calculated. There is a temperature cutoff to ensure that there is no harm done to the rat. 

Project Objective:

The objective of this project is to build a testing instrument for human trials, inspired by the current design for laboratory animals. In a similar method to the animal trials, focused heat will be applied to the human patient's finger in a glass contact experiment and in a non-contact experiment . The apparatus should be able to lift the patient's hand and hold it steady for the non-contact experiment. The glass surface should be heated to 30°C before focused heat is applied so that the patient's hand is acclimated. Once the experiment begins, temperature and reaction times will be recorded and a similar temperature cutoff will be implemented. Temperature should be controllable by 1°C/second and heat should be applied on a 3-5 mm diameter point on the finger. The apparatus should also be a "black box" design to minimize bias. An apparatus for focused cooling rather than heating is also desired.

Final Design: 

Our final design of the Neuropathy Diagnostic Device consists of two main parts: the circuit and the form factor. Appropriate sensors are part were chosen to ensure a fast testing that suits any hand. The following figure depicts all of circuit components wired up and ready to use, although it has been removed from our physical housing for clarity.

In a brief overview the circuit works in the following way:

• 1. Operator switches on the power, and the Arduino immediately enacts a controller to send signals. The fan disperses the warm air. The controller will continue to run and maintain the housing at 30 degrees C. Sensor data is taken from thermistors to calculate the error in the controller.

  2. The operator will position the patient’s hand and the heating source 

  3. A start button is pushed: the ultrasonic sensor calibrates the distance to the patient, and the focal heat source begins heating the finger at 1 deg C/sec.

  4. Once the patient feels the heat and lifts his/her hand, the motion sensor will send signals back to the arduino. Then, the focal heat source will turn off and the Arduino will send the time of the test and the temperature to the LCD screen. 

  5. The system resets, and maintains the housing at 30 degrees until power is removed. The LCD will indicate when it is ready for a new test to start.

The form was very similar to the setup of the original rodent testing boxes. Its dimensions are 11’’  x 11’’ x 6’’ high. This is still rather large, but was designed at first so any hand, despite of its size, could rest comfortably on the glass on top. The following picture shows the first prototype.