This protocol presents the first visual methodology for etching and cutting plain and dyed Aerogel using a laser engraving system. The main advantage of this technique is its simplicity as it allows Aerogel monoliths of any shape, size, or color to be etched. Video presentation allows demonstration of the practical considerations of the protocol, including placement of the Aerogel and alignment of the laser cutter.
To prepare a mold for Aerogel monolith fabrication, select a three-part steel mold consisting of a top, middle, and bottom part with outer dimensions of 15.24 by 14 centimeters in a 10 by 11 centimeter cavity in the center. The top part of the mold should have seven 0.08 centimeter vent holes on each side. Use diluted soap and a rough textured sponge to scrub the top, middle, and bottom parts of the mold and dry all of the clean parts of the mold with a paper towel.
After drying, use individual disposable acetone-dipped cleaning wipes to wipe the mold until the cleaning wipe remains clean. Next, use 2, 000 grit sandpaper to lightly sand all of the surfaces until the mold is smooth to the touch and any residue from previous uses has been removed, paying extra attention to the inside of the middle mold where the Aerogel is formed. Clear the vent holes on the top mold part with compressed air and manually apply approximately 2.4 milliliters of high vacuum grease in a thick, even one to two millimeter layer over the entire top connecting surface of the bottom mold and approximately one milliliter of grease in a thick, even one to two millimeter layer to the outer half of the bottom connecting surface of the top mold.
Apply approximately 0.5 milliliters of high vacuum grease in an even less than 0.5 millimeter layer to the inside surfaces of the top and bottom molds and use a disposable cleaning wipe to wipe away excess grease until the surface feels smooth and no stickiness from the grease remains. Manually apply 0.5 milliliters of high vacuum grease in an even less than 0.5 millimeter layer of grease to the inside surface of the middle mold. To prepare the etching pattern file, open a new document in an appropriate drawing application and add the desired text or image of any size and line width directly to the document, then save the file.
To etch an Aerogel monolith, first turn on the laser engraver, vacuum exhaust system, and attached computer. Measure the size of the Aerogel monolith surface that will be etched and open the etching pattern file. Set the document's dimension size to correspond to the measured Aerogel monolith size and open the lid of the laser engraver.
Use a gloved hand to place the Aerogel onto the laser engraver platform and align the Aerogel on the top left corner with the Aerogel touching the top and left rulers. Flip the V-shape magnet manual focus gauge attached to the laser upside down and press Focus on the laser engraver. Protect the Aerogel monolith with a disposable cleaning wipe and use the up arrow on the laser engraver control panel to move the laser engraver platform until the bottom part of the manual focus gauge just touches the Aerogel.
Remove the wipe and return the gauge to its original position. Close the laser engraver lid and click File and Print in the drawing program. Select the laser engraver as the print location and open the preferences window to set the printer properties.
Select the raster mode inside a DPI of 600, a speed of 100%and a power of 55%Confirm that the piece size matches the measured Aerogel monolith size and click Apply and Print. On the front panel of the laser engraver, click Job and select the corresponding filename. Click Go.When the laser engraver finishes, click Focus and use the down arrow on the laser engraver front control panel to lower the base.
Use a gloved hand to gently transfer the Aerogel from the laser engraver platform to its container and click Trash to purge the job from the engraver. To cut an Aerogel monolith, turn on the laser engraver, vacuum exhaust system, and attached computer and measure the size of the Aerogel monolith surface to be cut. For general cutting, open a new document in the drawing program and enter the dimensions for the document size to correlate with the measured Aerogel monolith size.
Use the hairline width drawing tool to create the pattern that will be cut and position the pattern to match the desired cut location on the Aerogel. Clean a 0.0127 millimeter thick sheet of stainless steel foil large enough to cover the base of the Aerogel monolith with acetone and place the foil onto the laser engraver platform. Align the Aerogel and stainless steel foil in the top left corner with the Aerogel touching the top and left rulers and adjust the gauge position as demonstrated.
Click File and Print in the drawing program and select the laser engraver as the print location and open the preferences window to set the printer properties. Select the vector mode and set the DPI to 600, the speed to 3%the power to 90%and the frequency of 1, 000 Hertz. Confirm that the piece size matches the measured Aerogel size.
The depth of the cut will vary with the laser speed. Click Job and Go to initiate the cutting as demonstrated. After collecting the sample, use a foam brush to gently remove any small pieces of ablated Aerogel left on the face of the monolith that was in contact with the laser.
For this Aerogel mosaic approach, the same pattern was cut into three different dyed Aerogel monoliths and the pieces were reassembled into a mosaic pattern. It is possible to etch designs on smaller monolithic pieces as demonstrated to obtain visually interesting arrangements under natural and ultraviolet light conditions even on smaller pieces. As illustrated, native Aerogels can be etched with patterns of various density with photographs printed onto the front surface of a planar Aerogel, onto a curved surface, and onto fluorescent dyed Aerogels.
In this scanning electron microscope image of an etched silica Aerogel, the interface between the etched lines and the almost smooth unetched nanoporous Aerogel can be observed. Etching causes the ablation and melting of the surface material into filament-like structures as observed in this image showing the effect of a single laser pulse of the Aerogel. Careful preparation, including contrast adjustment of the images to be etched, is critical to achieving high-quality results.
Further refinement of the laser etching method could provide an alternative to micro-machining of the silica Aerogels. Aesthetic Aerogel monoliths could find application in a wide variety of areas, including artwork and sustainable buildings.
