Droplet generator test with pressure driven pump

We were successfully able to generate water droplets using our custom pressure driven pump

Droplet generation

This video shows droplet generation in the T-junction device. These droplets will be used to demonstrate the functionality of the analog subsystem for impedance testing, control system for droplet generation speed and the microfluidics chip for creating the droplet. This video is being used to show that the device design is performing as expected.

The base liquid is oil which is in the straight channel. Water is coming in from the left side and forms droplets in oil. 

Preliminary testing: Gradient device

In this video, the gradient device made over spring break is being tested. The test is to show that the different color combinations can be made by using laminar mixing in a microfluidic chip. Two different dyes were used to create two solutions for the input into the chip. As the clip shows, the two extremes outlets are going to be the original input colors and the the middle outlets are going to have a different mixing concentration of the two.

A few things to note-
1. Our input driving system is a pressure driven pump (instead of a conventional syringe pump) to flow the fluids into the chip. As the moment the input pressure for each reservoir were set to be different, which affects the mixing ratios between the colors. This is show that our system can replace the pre-existing system.

2. Leakages at the outputs will be seen and are due to larger tube size. In the future that will be fixed.

Clipping circuit

Tested a clipping circuit to protect the Arduino input pins from overvoltages. The Arduino Due pins cannot handle voltages above 3.6V or below -0.3V. ADC values are clipped at 3.3V and 0V. The Zener diode used is the 1N5227, and has a Zener voltage of 3.6V.

This resulted in the following waveforms, yellow being input to the clipping circuit and green being the output the Arduino would read.

These 10000 datapoints were used to create an equation to map the Arduino read voltages to the actual unclipped values:

y = 0.0872x3 - 0.2738x2 + 1.2169x

This trendline has an R^2 of 0.9993

Manifold Problem

The manifold that was ordered is meant for SY valves and is apparently incompatible with VQ valves. The pressure, return, and outlet lines are in a different order within the valves, as per their datasheets:

Updated quadrature sweep

Soldered Vcc to the node determined by Dr. Palermo. Fixed the random 5 MHz update at the end, and adjusted the formula to make each frequency pretty much exact (within 1%). Moved all the frequency updating and impedance reading to a timer interrupt, so there's now room in the main loop for pressure control.

Quadrature Sweep Video

After 10 MHz it goes to 5 MHz for some reason, I'll have to look into that.

Pressure sensor and reservoir testing

Last week, Taylor and I tested the pressure sensor (PSE 532 M5) and the centrifuge reservoir. The pressure sensor works well and gives very stable readings. The rate of change of pressure (positive and negative) were calculated and will be used for calibration.

Updated LabVIEW Interface once again

Today I made an Arduino program and corresponding LabVIEW program to display pressure over time received from the pressure sensor. This will be used tomorrow to plot how the pressure changes in the reservoir when we open and close the valve to the pressure line.

The LabVIEW interface has been updated again, and I moved all the magnitude and phase calculations from the Arduino to LabVIEW. Now the Arduino simple takes the measurement and sends that raw 12-bit number to LabVIEW for processing and display.

Programmed the AD9850 eval board

The AD9850 has been programmed to do a logarithmic frequency sweep from 10 kHz to 10 MHz. A million times easier than the old frequency generator.

Updated LabVIEW Interface

LabVIEW interface

Experimental setup for external reservoir

The following setup is going to serve as an external source for introducing fluids in the device by controlling the pressure reading inside the container.