Integrated System Build & Test with Customer Demo
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Team Vision for System Level Demo with Customer
Our team planned to begin integration and prepare a demo prototype for our customer. This includes taking the mechanical, electrical, and biological systems and bringing them together to create a functioning product.
The team was able to partially complete this, as we have partially integrated subsystems and some hints of success through dielectrophoresis. The prototype is in progress.
- Further testing has been completed with the stepper motor, getting four of the switches to work, integration with pushing fluids into the channels using the correct rotation speeds (calculation of Reynolds flow), and integrated with its' own power system to function as if it were in the assembly. The buttons work in the following order:
- Adjust syringe length Forwards
- Adjust syringe length Backwards
- Start button (*45 min cycle)
- Stop button
Microchannel Fabrication TestingThe following are iterations of the methods we have employed to create the microfluidic devices. Several issues have occurred throughout this process, including that the PDMS does not fully seal to the glass slide, and that the electrodes are not tightly fit into the PDMS, so fluids can leak from the channel to the top of the device. In all cases below, the electrode slits are punched out using a 1mm biopsy punch. Below shows the attempts made to mitigate these issues:
MicrosealThe Microseal uses a technique where the electrodes are then placed into the slit, and liquid PDMS (5-10uL) was then carefully pipetted onto the contact points between the electrodes and the top of the solid PDMS. The main issue that occurred was that the seal was not strong enough, and even a slight movement of the electrode was enough to break seal. This is not a robust solution.
Electrode Dipping uses a technique where the electrodes were dipped into liquid PDMS and were allowed to cure upside down using an oven. This created a strong seal, however liquid PDMS was able to get into the channel and cure inside. This sealed the channel from the inside and prevented fluid flow within.
PDMS dripping uses a technique where the electrodes were inserted directly into the slits, and then liquid PDMS was dripped on top of the device to the coat the surfaces surrounding the electrodes. This method allowed liquid PDMS to get into the channel and cure inside. This sealed the channel from the inside and prevented fluid flow within. Additionally, it caused an uneven surface above the channel, which may have influenced our ability to view the separation within the channel due to refraction.
PDMS on PDMS Curing
PDMS on PDMS curing is a method which we placed the electrodes into the slit, then poured liquid PDMS over the entire device while tubes were placed into the inlet and outlet ports. When the PDMS had cured, liquid PDMS had gotten into the channel and cured inside. This sealed the channel from the inside and prevented fluid flow within.
Silicone Sealant is a method where the electrodes were placed into the slits, and an off the shelf silicone seal was manually squeezed onto the surface of the solid PDMS and placed around the electrodes. The seal created from this was inconsistent and the material itself was challenging to work with. The sealant dried nearly clear, but added some refraction to the light when trying to look at the channel through the microscope.
Room Temperature Electrode Dip
This method was used to try to prevent PDMS was curing inside the channel during the Electrode Dipping process. The same method was used, however DI water was forced into the channel to attempt to prevent PDMS from filling that space.This cured at room temperature to prevent the heat application from evaporating the water. Liquid PDMS was still able to get into the channel and cure inside. This sealed the channel from the inside and prevented fluid flow within.
Test Results Summary
- This test integrated three of our systems, the circuitry with Arduino (1.), syringe pump (2.), and channel (3.). This test was successful in that the stepper motor was able to control our syringe pump, the syringe pump was then able to pump fluid through tubing into our channel, and the fluid was able to successfully be driven through the inlet of our device to the outlets, without leakage.
- In the video below, fluid flow caused by the syringe pump through the microchannel can be visualized with the assistance of 1 um green polystyrene particles.
- After this, a 7 V DC signal was applied without flow from the syringe pump. Some difficulty was had attempting to cause eDEP with an AC signal both with and without fluid flow, which is why the DC signal was used.
- Later, with a new microchannel, AC eDEP was tested again. In the case below, fluid flow was at maximum velocity as the video starts. 20 seconds in, a 40 Vpp 1 kHz was applied. No DEP can be observed in this condition.
- In the video below, no signal or fluid flow occurs at the beginning. 5 seconds in, a 40 Vpp 1 kHz was applied and DEP can be observed. 15 seconds in, the syringe pump was turned on. As the fluid flow reaches a certain velocity, DEP can no longer be observed.
- Afterwards, no signal or fluid flow occurs at the beginning. 5 seconds in, a 40 Vpp 1 kHz was applied and DEP can be observed. 15 seconds in, the syringe pump was turned on at half the velocity. At this velocity, fluid flow is very choppy due to the nature of the syringe pump. DEP seems to be observable throughout all fluid flow velocities.
Plans for next phase
- Vincent Serianni
- Tyler Lisec
- Alexandra LaLonde
- Chris Molinari
- As an individual on the team, what are you doing to help your team achieve these goals? (Use the individual 3-week plan template for this)
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