Project

# Title Team Members TA Documents Sponsor
66 A New Approach to an External Ventricular Drain (Capstone Project)
David Kapelyan
Isiah Lashley
Ralph Nathan
Jason Jung design_document1.pdf
final_paper1.pdf
grading_sheet1.pdf
proposal1.pdf
video
Team Members:
- Ralph Nathan (ralphn2)
- David Kapelyan (davidik2)
- Isiah Lashley (ilashl2)

# Problem
External Ventricular Drains (EVDs) are used to drain cerebrospinal fluid (CSF), but if done incorrectly, they can cause severe damage, including death. To ensure the correct amount of CSF is drained, the pressure transducers on the EVD must be properly zeroed. However, patients often move during sleep or daily activities such as showering, which can lead to incorrect pressure readings and improper CSF drainage. According to Dr. Suguna Pappu, there have been numerous cases where approximately 40 ccs of CSF were drained instead of the intended 10 due to zeroing errors. This, again, can result in significant harm or even death.
In summary, a new approach to EVDs is necessary, one that provides stable pressure readings even when the patient is in motion. This capstone project aims to create advancements in EVDs.
# Solution
We plan to utilize an STM32 microcontroller to process input from a pressure transducer connected to the catheter through which cerebrospinal fluid (CSF) is drained from the brain. Our design will incorporate a pipe tee in series with a two-way solenoid valve. The catheter extending from the skull will be connected to the tee, which will also be fitted with a pressure gauge. This pressure gauge will be linked to the microcontroller, which will control whether the solenoid valve is open or closed. Measuring pressure digitally, rather than using a manometer, will eliminate the issue of set-point shifts caused by patient movement. Additionally, there will be no need to manually set a “zero” point, as this can be calibrated in software.
We will use an instrumentation amplifier with a shunt resistor to buffer signals from the pressure transducer, ensuring accurate readings by the microcontroller. Digital signal processing (DSP) will then be performed via the microcontroller, including noise filtering, adaptive thresholding for real-time pressure management, and data logging of pressure readings. The system will regulate the flow of CSF to a drain collection bag via a push-connected solenoid valve. The microcontroller will communicate with a display or bedside monitor via Bluetooth, presenting pressure data—including real-time pressure graphs, an alarm system for abnormal pressure readings, and data logs for physician review—through a graphical user interface (GUI). Additionally, we will implement fail-safes to prevent over-drainage or blockage and include a manual override in case of system failure.



# Solution Components

## STM32 Microcontroller
An STM32 microcontroller with an on-package RF transceiver that supports Bluetooth will be utilized. The ADC of the controller supports a resolution of 12 bits which will be useful for accurately measuring the output signal of our pressure gauge. The STM32 Microcontroller comes with an internal reference voltage that is typically derived from the supply voltage.


## Power System Circuit
A high-voltage rail powered by an AC-DC wall adapter will be used to power the board. A linear regulator will be utilized to decrease the voltage such that it can be used to power the microcontroller.

## Push Connect Solenoid Valve For Drainage
A switch will be placed between the high-voltage rail and the solenoid input. The switch will be controlled by an output signal from the microcontroller.

## Pressure Transducer
The pressure transducer will be connected to the pipe tee. The pressure transducer will need to be a precision pressure transducer as the standard Intracranial Pressure is approximately 16mg(0.309 PSI) which is a relatively low pressure. The transducer will have a current output which will be connected to a shunt resistor across which the voltage will be measured using an instrumentation amplifier.

# Criterion For Success

A successful project will result in a device that accurately reads and processes pressure data from a transducer with minimal noise and high precision. The system must effectively regulate cerebrospinal fluid (CSF) drainage by dynamically controlling a solenoid valve to maintain an average outflow of 10cc/hour, preventing over-drainage or blockage. Additionally, the microcontroller must wirelessly transmit real-time pressure readings via Bluetooth to a bedside monitor, where a graphical user interface (GUI) will display real-time pressure graphs, generate alarm notifications for abnormal pressure levels, and log data for physician review. To ensure safety and reliability, the system must incorporate fail-safes to prevent malfunctions and provide a manual override for emergency control. By meeting these criteria, the project will achieve its goal of delivering an automated, accurate, and user-friendly solution for CSF drainage management.

# Parts:
STM32
PCB
Push Connect Solenoid Valve
Pipe Tee
Pressure Transducer
Instrumentation Amplifier

Links:

¼” push connect solenoid valve
⅛” npt solenoid valve

https://www.omega.com/en-us/pressure-measurement/pressure-transducers/px119/p/PX119-015GI

https://www.coleparmer.com/i/cole-parmer-0-25-accuracy-transmitter-0-to-2-psi-4-to-20-ma-output/6807503

https://www.mouser.com/ProductDetail/Analog-Devices/ADR435BRZ?qs=WIvQP4zGanhj7%2FQWeFYslw%3D%3D&utm_id=22030944703&gad_source=1&gclid=CjwKCAiAtYy9BhBcEiwANWQQLyuDFchHNWjCoLscoWoVpM2fdflY2CcCi-fQ9bxPrEm5EPQFvoIeNxoCPqgQAvD_BwE

Four Point Probe

Simon Danthinne, Ming-Yan Hsiao, Dorian Tricaud

Four Point Probe

Featured Project

# Four Point Probe

Team Members:

Simon Danthinne(simoned2)

Ming-Yan Hsiao(myhsiao2)

Dorian Tricaud (tricaud2)

# Problem:

In the manufacturing process of semiconductor wafers, numerous pieces of test equipment are essential to verify that each manufacturing step has been correctly executed. This requirement significantly raises the cost barrier for entering semiconductor manufacturing, making it challenging for students and hobbyists to gain practical experience. To address this issue, we propose developing an all-in-one four-point probe setup. This device will enable users to measure the surface resistivity of a wafer, a critical parameter that can provide insights into various properties of the wafer, such as its doping level. By offering a more accessible and cost-effective solution, we aim to lower the entry barriers and facilitate hands-on learning and experimentation in semiconductor manufacturing.

# Solution:

Our design will use an off-the-shelf four point probe head for the precision manufacturing tolerances which will be used for contact with the wafer. This wafer contact solution will then be connected to a current source precisely controlled by an IC as well as an ADC to measure the voltage. For user interface, we will have an array of buttons for user input as well as an LCD screen to provide measurement readout and parameter setup regarding wafer information. This will allow us to make better approximations for the wafer based on size and doping type.

# Solution Components:

## Subsystem 1: Measurement system

We will utilize a four-point probe head (HPS2523) with 2mm diameter gold tips to measure the sheet resistance of the silicon wafer. A DC voltage regulator (DIO6905CSH3) will be employed to force current through the two outer tips, while a 24-bit ADC (MCP3561RT-E/ST) will measure the voltage across the two inner tips, with expected measurements in the millivolt range and current operation lasting several milliseconds. Additionally, we plan to use an AC voltage regulator (TPS79633QDCQRQ1) to transiently sweep the outer tips to measure capacitances between them, which will help determine the dopants present. To accurately measure the low voltages, we will amplify the signal using an JFET op-amp (OPA140AIDGKR) to ensure it falls within the ADC’s specifications. Using these measurements, we can apply formulas with corrections for real-world factors to calculate the sheet resistance and other parameters of the wafer.

## Subsystem 2: User Input

To enable users to interact effectively with the measurement system, we will implement an array of buttons that offer various functions such as calibration, measurement setup, and measurement polling. This interface will let users configure the measurement system to ensure that the approximations are suitable for the specific properties of the wafer. The button interface will provide users with the ability to initiate calibration routines to ensure accuracy and reliability, and set up measurements by defining parameters like type, range, and size tailored to the wafer’s characteristics. Additionally, users can poll measurements to start, stop, and monitor ongoing measurements, allowing for real-time adjustments and data collection. The interface also allows users to make approximations regarding other wafer properties so the user can quickly find out more information on their wafer. This comprehensive button interface will make the measurement system user-friendly and adaptable, ensuring precise and efficient measurements tailored to the specific needs of each wafer.

## Subsystem 3: Display

To provide output to users, we will utilize a monochrome 2.4 inch 128x64 OLED LCD display driven over SPI from the MCU. This display will not only present data clearly but also serve as an interface for users to interact with the device. The monochrome LCD will be instrumental in displaying measurement results, system status, and other relevant information in a straightforward and easy-to-read format. Additionally, it will facilitate user interaction by providing visual feedback during calibration, measurement setup, and polling processes. This ensures that users can efficiently navigate and operate the device, making the overall experience intuitive and user-friendly.

# Criterion for Success:

A precise constant current can be run through the wafer for various samples

Measurement system can identify voltage (10mV range minimum) across wafer

Measurement data and calculations can be viewed on LCD

Button inputs allow us to navigate and setup measurement parameters

Total part cost per unit must be less than cheapest readily available four point probes (≤ 650 USD)

Project Videos