Project

# Title Team Members TA Documents Sponsor
1 A Compact Material Modulus Measurement Instrument
 Kongning Lai
Tianyu Fu
Yunzhi Lu
Ziyi Lin
 design_document1.pdf
design_document2.pdf
design_document3.pdf
proposal1.pdf
 Huan Hu
# Problem
Soft materials, including hydrogels and polymers, are widely used in fields such as biomedicine, protective coatings, and electronics. Their mechanical modulus is a key parameter for precise design. However, challenges arise in the measurement process. The system will apply a resistance bridge as a sensor. However, there is a basic zero shift. As the measurement process continues, the shift will accumulate due to temperature and other factors. The accumulated shift may exceed the practical requirements of the experiment, leading to potential inaccuracies. Furthermore, there is no software available for accurately performing baseline correction, contact point estimation, and contact model selection on force-displacement curves obtained from new instruments, further complicating precise measurements.

# Solution Overview
This project aims to develop a macro-scale instrument replicating the functionality of an atomic force microscope (AFM) for measuring the mechanical modulus of soft materials. To mitigate the issue of zero shift, the project will develop a feedback system to control the shift and ensure the resistances are balanced. The approach begins by implementing AFM data processing functions using Python, providing a foundation for accurate analysis. Building upon this, machine learning techniques will then be integrated to enhance both the speed and accuracy of the measurements, ultimately improving the reliability of soft material characterization.

# Solution Components
## Subsystem1 (Hardware)
### Part A
- Multiple positioning stages: Provide precise control over specimen alignment and movement.
- Metal cantilever with adhesive-attached balls: Adhesively attached balls ensure uniform force distribution.
- Strain gauge for measuring both strain and force: Ensures accurate data collection for analyzing material properties.

### Part B
- Wheatstone Bridge used to measure resistance variations.
- Differential Amplifier with a Reference Voltage Source, Amplifies the signal and stabilizes the system.
- Voltage-Controlled Resistor (VCR) is used to adjust the bridge balance dynamically to compensate for zero shift.

## Subsystem2 (Software)
### Part A
- Python code for data preprocessing. The process begins with raw FZ curve input, followed by baseline correction, contact point estimation, and feature extraction.
- A Linear Discriminant Analysis (LDA) classifier will be used to determine the contact model based on features extracted from force-displacement (FZ) curves.

### Part B
- A PC-based AFM control software with a graphical interface using an STM32 development board as the lower controller and QT as the upper controller.
- The software will generate control signals for the motor and receive strain gauge signals from the system.
- It will calculate displacement based on motor speed and force from strain gauge readings. The force-displacement curve will be displayed in real time and saved locally, providing input for the LDA classifier.

# Criteria of Success
The mechanical system must reliably generate precise and controllable force curves while the metal cantilever with glued balls maintains a consistent contact geometry, ensuring that variations in the force-indentation response are solely due to the material properties. Additionally, active compensation with a voltage-controlled resistor must be implemented to eliminate zero shift error, maintaining the accuracy of measurements. Furthermore, preliminary data processing on collected force-displacement curves must be conducted accurately and robustly to ensure reliable analysis and interpretation.

Prosthetic Control Board

Featured Project

Psyonic is a local start-up that has been working on a prosthetic arm with an impressive set of features as well as being affordable. The current iteration of the main hand board is functional, but has limitations in computational power as well as scalability. In lieu of this, Psyonic wishes to switch to a production-ready chip that is an improvement on the current micro controller by utilizing a more modern architecture. During this change a few new features would be added that would improve safety, allow for easier debugging, and fix some issues present in the current implementation. The board is also slated to communicate with several other boards found in the hand. Additionally we are looking at the possibility of improving the longevity of the product with methods such as conformal coating and potting.

Core Functionality:

Replace microcontroller, change connectors, and code software to send control signals to the motor drivers

Tier 1 functions:

Add additional communication interfaces (I2C), and add temperature sensor.

Tier 2 functions:

Setup framework for communication between other boards, and improve board longevity.

Overview of proposed changes by affected area:

Microcontroller/Architecture Change:

Teensy -> Production-ready chip (most likely ARM based, i.e. STM32 family of processors)

Board:

support new microcontroller, adding additional communication interfaces (I2C), change to more robust connector. (will need to design pcb for both main control as well as finger sensors)

Sensor:

Addition of a temperature sensor to provide temperature feedback to the microcontroller.

Software:

change from Arduino IDE to new toolchain. (ARM has various base libraries such as mbed and can be configured for use with eclipse to act as IDE) Lay out framework to allow communication from other boards found in other parts of the arm.