Laser-Induced Graphene (LIG) Fabrication Process using GCC Laser @ CBA

This page documents the process of producing laser-induced graphene, in general, but also specifically using the GCC Spirit 30W 10.6 microns CO2 Laser at MIT CBA .

Introduction !

You might have heard of graphene , a wondrous material discovered in 2004 that was promised to save the world because it has a lot of really interesting properties. It has shown promise in everything from solar panels to thermal compounds energy storage to composites, biosensors, and others.

The difficulty is scaling up these graphene processes and their integration within existing fabrication processes! Producing high-quality single monolayer graphene requires advanced tools such as chemical vapor deposition (CVD) tools that you can find at MIT.nano, but today we are not doing this. I am going to introduce you to a type of graphene known as laser-induced graphene (LIG).

What is Laser Induced Graphene (LIG)? !

In 2014, researchers found that hitting a polyimide (Kapton) sheet with a CO2 laser will make it decompose into a graphitic substance! Upon further investigation, this graphitic carbon-based substance turns out to be a type of graphene named laser-induced graphene (LIG).

This forms a porous structure of foamy carbon wonder material!

This is very different from the monolayer graphene that you typically hear about, and it has some interesting properties relative to the monolayer.

History: Actually, the very first report of generating conductive material by irradiating a polymer with a laser dates back to 1991 when Schumann et al showed here and here but this was not LIG per se. The very first LIG was shown in this Nat. Commun paper by Tour’s group.

Properties of LIG

  • Electrical Conductivity: This makes it ideal for electronic and electrical applications.
  • Large Surface Area: Thanks to its porous structure, it's great for applications that require a high surface area like supercapacitors and biosensors.
  • Mechanical Flexibility: These properties make LIG suitable for a variety of applications, including flexible electronics.
  • Maskless patterning
  • Versatility in design
  • Scalable, low-cost fabrication

    The cool thing is that you are using a laser, so you can pretty precisely pattern where you want that graphene to go!

    Fabrication Process of LIG

    Now that we have discussed why LIG is a cool material let’s talk about how you can make your own LIG for your applications! The process is quite simple, you just need a piece of Kapton sheet and your favorite laser cutter!

    1. Starting with Carbon-rich Materials: Polyimide (specifically Kapton is commonly used. Note: Although Kapton is the most commonly used substrate, people have used other materials that include carbon precursors such as cloth, paper cardboard, and even food! (More here!) & Bio-LIG

    2. Laser Irradiation: A focused laser beam is directed onto the polyimide. The intense heat from the laser triggers a reaction in the material.

    3.Transformation into Graphene: The carbon atoms in the polyimide rearrange into a graphene structure. This form of graphene is porous and three-dimensional, unlike traditional flat monolayer graphene sheets. Note: In fact, you do not need a CO2 laser, the first report of LIG happened to be using a CO2 laser, but you can use UV, 405 nm, 450 nm laser diodes -- > ( I built a machine named lazerGraph based on Creality inexpensive laser module )

    Applications of LIG

    LIG's unique properties allow for its use in numerous fields: (Nice Review)

  • Electronics: In the development of flexible circuits, sensors & heaters.
  • Energy Storage: Padticularly in supercapacitors, where its high surface area is beneficial.
  • Environmental Applications: Including water purification, water splitting, and environmental monitoring.

    The cool thing is that you are using a laser, so you can pretty precisely pattern where you want that graphene to go!

    Demos

    Strain bend sensor --> my HTMAA input week assignment

    LIG Flex Sensor

    heater

    LIG at CBA Shop

    (LIG fabrication is all about finding the optimal parameter (power,speed,PPI) for your own laser tool !)

    General Notes:

  • An increase in power leads to an increase in the ablation effect at the surface of PI. Using too much power will cut through the PI sheet. Similarly, decreasing the speed will irradiate the PI sheet too deep to the point it might cut through the PI sheet completely. Thus, the optimal condition is usually a sweet spot combining low power and speed
  • The pulse per inch (PPI) paramater is chosen to be at its maximum since we want the generated pattern to be as dense as possible.
  • PI sheet thickness used here was 125 μm, but LIG can also be genertaed from other thinner sheets such as 50 μm and 25 μm. ( power and speed % might need to be adjusted slightly)
  • I use a thick 8mm acrylic substrate as a holder to fix the PI sheet on top of it uniformly. Make sure to use tape from all sides and ensure there are no bubbles or uneven bent areas

    Current parameters

  • Laser tool:GCC (Spirit GLS-30v)
  • Polyamide sheet thcikness : 125 μm
  • Power : 8%
  • Speed : 10%
  • PPI : 1500
  • Print DPI : 1500

    Notes:
  • An increase in power leads to an increase in the ablation effect at the surface of PI. Using too much power will cut through the PI sheet. Similarly, decreasing the speed will irradiate the PI sheet too deep to the point it might cut through the PI sheet completely. Thus, the optimal condition is usually a sweet spot combining low power and speed
  • The pulse per inch (PPI) paramater is chosen to be at its maximum since we want the generated pattern to be as dense as possible.
  • The CorelDraw Dots per Inch (DPI) parameter was also chosen to be as large as possible to ensure that the printed file sent from CorelDraw has as many details as possible.
  • PI sheet thickness used here was 125 μm, but LIG can also be genertaed from other thinner sheets such as 50 μm and 25 μm. ( power and speed % might need to be adjusted slightly)
  • I used a thick 8mm acrylic substrate as a holder to fix the PI sheet on top of it uniformly. Make sure to use tape from all sides and ensure there are no bubbles or uneven bent areas

    Some Issues !

    After fixing the laser setting parameters above, I decided to laser-scribe an array of 81 electrodes with an identical length (22 mm) and width (2mm) each. The idea was to measure the resistance of each generated electrode in order to test the consistency of the process.

    For the most part, the majority of the electrodes looked visually the same. However, when I took a closer look, I found that some electrodes had some striation patterns that are repeated. This might indicate some defects in the laser engraving paths.

    Measuring variabilities

    Most importantly, the resistance readings of the electrodes show measured resistance readings as high as 374 Ω to as low as 201 Ω for electrodes of the same length and width! Having fixed all other parameters leaves us with the z height as the main parameter that might be changing from one sample to another. Testing the z bed leveling with the manually focusing tool across different bed areas confirmed that there is variability in height. Although these variations are in the mm range, their effect on the graphene generation process is pronounced since the generated graphene layers are in the micrometer range.

    Some electrodes actually had too many striations to the point where the electrodes were completely broken. Those electrodes are marked in red below

    Next steps

  • Build a core XY laser engraver based on a low-cost 405-450 nm laser diode module laser diode module (these range of powers and wavelengths were successfully reported in the literature to generate laser-induced graphenep[1 , 2 ,3 ] )--> Having a tabletop machine dedicated for LIG will ensure control over the bed height/leveling at all times