This week I learned how we will be fabricating our membrane. Last week, I described how we want a membrane that has hierarchical roughness. Which means it will have an inner core with pores and an outer core with even larger pores. Like this 

So the method we will be using is called electrospinning. It is a technique that can create fibers with diameters as small as a few nanometers. You can really see how small the fibers are in comparison to a human hair below.

To gain an understanding of the process I read a review article about all the possibilities of electrospinning which include optoelectronics, sensor technology, catalysis, filtration, and medicine.    Well the setup seems quite simple, but there are several variables that can be manipulated  to change  the product made.

There is not a protocol yet for what he wants to accomplish so we are meshing together the procedures from a few articles on electrospinning polyvinylidene flouride (PVDF) membranes. So my mentor and I set out on an engineering adventure with a scientific article in hand to attempt to bring his plan to life.

This is how I would sum it.

Step 1.

Create a solution of  whatever you want your fibers to be composed of. In our case it is a PVDF solution. We are using this polymer because of its resistance to harsh chemicals. It took 2 days just to prepare the solution! We will be testing several variables and the concentration of the PVDF solution is one those. We prepared a 15% and a 10% solution.

Step 2.

Place your polymer solution in a syringe that is placed in an automatic pump. Set up the electricity. We set our electric field at 20  kV or 20,000 volts. The applied voltage causes the solution to be pulled from the positive to negative electrode. As you increase the voltage the shape of the polymer will change from a cone to a jet and cause your product to change.

Step 3.

Start the pump and when you see the solution exiting the nozzle of your syringe turn on the electricity. Watch and wait for your fibers to collect. The spinning process took about 3 hours total for 3 ml of solution.

Like I said the process seems very simple, but is very complex due to all of the variables that can be manipulated. The distance the nozzle is from the collecting plate, the humidity, the rate of the pump, the size of the syringe, the electric field all play a major role in the fiber formation.

Next,  we will use the Scanning Electron Microscope (SEM) to take images of our membranes to compare the two solution fibers.

We will also be trained on a special elctrospinning set up that will allow us to take control of many of the variable mentioned before.

This week I have learned to importance of the doing background research because we have had to rely heavily on the work of others. I have also learned the importance of my engineering notebook. Everything we do is recorded in the notebook and will not only help us but serve as a guide to others.  This experience has given me a concrete experience, so I can better teach my students the engineering process.