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How to install electrospinning setup

For setup a simple electrospinning system by syringe pumps and high voltage power supply Please note the following.

  • In this syringe pump can be placed one or two syringes. Connect two syringes increase the content of nanofibers. However, due to the interaction of polymer jets in each nozzle, may be changed the nanofiber size and morphology. Therefore for the optimization process using one syringe is recommended. If you use more than two syringes, the distance between two nozzles should be at least 5 cm. Although depending on the polymer, voltage and, ... this could be less or more.

  • Distance between the nozzle head to collector is called "electrospinning distance". This distance is usually between 7 to 20 cm. this distance depending on the conditions could be less or more. In most systems, the collector is grounded. However, connecting a negative voltage to the collector can have interesting results.

  • Before starting, be sure the machine is properly earthed.

  • Due to electrical conductivity of most solvents, electricity will be transferred to the syringe through the hose. So when filling syringes be careful do not wet the syringes with polymeric solution. Otherwise, "high voltage" discharge noise will be heard on the pump. In this case turn the HV off and clean the syringes immediately.

  • Most existing hose lacks sufficient strength to prevent high voltage electricity, so the hose should be avoided to connect to other devices such as syringe pumps.

  • Improper use of the HVPS can the risk associated with electric shock and death. While using, all the safety measures to be considered.

 

 

Protocol: Electrospinning Fundamentals: Optimizing Solution and Apparatus Parameters1

    1.      Choose a Polymer

    1.1.   Choose a polymer (e.g., poly-L-lactic acid (PLLA), polycaprolactone (PCL), polystyrene (PS) or nylon) based on your specifications (e.g., biodegradable, thermoplastic or cross-linkable) and a solvent of that polymer. Choose suitable personal protective equipment based on your selection.

    1.2.   Select a substrate based on your application (e.g., glass, plastic, metal or silicon wafer).

    2.      Choose a Collector

    2.1.   Choose the collector geometry based on your specifications. Random fibers can be collected on stationary plates. Aligned fibers can be collected on rapidly rotating wheels, drums or rods, or on parallel plates.

    2.2.   The collector must be conductive and must remain isolated from its axel in such a way that it can be grounded without also grounding adjacent objects, the table top, etc.

    3.      Approximate the Critical Entanglement Concentration Empirically

    3.1.   Prepare several candidate polymer concentrations (e.g., 4, 10, 15, 20, 30 wt%) and choose a concentration that flows (the solution should be a viscous liquid but not a gel) to start with.

    3.2.   Set up the electrospinning apparatus

    3.2.1.      Load the syringe pump and set the pump speed such that any bead of solution wiped from the tip is immediately replaced.

    3.2.2.      Ground the collector and clip the high voltage wire to the conductor plate (a small square of conductive material such as aluminum foil through which the syringe tip protrudes).

    3.2.3.      Start the wheel spinning.

    3.2.4.      Make sure the power supply is set to zero before turning it on.

    3.3.   Observe the stream

    3.3.1.      Ramp voltage up slowly and watch the bead of the solution at the needle tip.

    3.3.2.      Adjust the voltage to obtain a long and steady stream. If a steady stream cannot be obtained, adjust the polymer solution concentration.

    4.      Troubleshooting - the Stream:

    4.1.   Trouble viewing the stream

    4.1.1.      Use a dark matte backdrop and place a unidirectional light source (such as a flashlight) between the viewer and the stream.

    4.2.   Dripping from the syringe tip

    4.2.1.      If the polymer solution is dripping straight down with no attraction to the wheel, make sure the conductor plate is making contact with the needle tip and that the collector is making contact with ground.

    4.2.2.      If the drop of polymer solution at the syringe tip is leaning in the direction of the wheel but is not forming a stream, increase the voltage. The quality of the stream can be adjusted by varying the distance and the voltage until a steady stream is visible.

    4.3.   Large globs at the syringe tip
    when the polymer solution begins to collect and harden at the tip of the needle, swipe the glob away with a paper towel attached to a non-conductive stick.

    4.4.   Oscillating or 'wagging' streams
    when the stream is wagging up and down rapidly turn down the voltage or increase the distance between the syringe tip and the wheel. If the stream continues to wag use a higher concentration of polymer or add a little solvent with a slower evaporation.

    4.5.   Short or discontinuous streams
    visible steady streams making observable contact with the wheel set at a high rotational velocity yield the highest quality of uniformity and alignment. When the stream is short and discontinuous, increasing the polymer solution, adding more slow evaporating solvent, and adjusting the voltage will improve the length and steadiness of the stream.

    5.      Troubleshooting - Fiber Morphology

    5.1.   Beading
    when beads are discovered in the fibers, increase the polymer solution and make sure the conductor plate is making continuous contact with the needle and that the grounded wire brush is making continuous contact with the wheel.

    5.2.   Ribbons and bleeding fibers
    when fibers are forming as ribbons or are bleeding together, use a higher concentration of polymer or a solvent with a higher rate of evaporation (more volatile).

    5.3.   Curlicue or wavy fibers
    when fibers are forming waves or curlicues increase the wheel speed or move the needle tip further from the collector. Also, check that the conductor plate and collector are not vibrating.

    5.4.   Porosity
    if pores are desired, use a rapidly evaporating solvent. If pores are not desired, try adding a small amount of co-solvent that is less volatile than the major solvent.

    5.5.   Alignment
    when the collector is moving at a low RPM or at rest, the alignment quality is poor. Increase the alignment by increasing the speed of the wheel.

 

1: Michelle K. Leac; et al; The Journal of Visualized Experiments (JoVE)

 
   
 

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