Fabrication

As mentioned previously, there are many variations of designs and materials for dielectric elastomer actuators, which can require different techniques to create. The following section provides step by step instructions on the manufacture of a circular dielectric elastomer actuator on a rigid frame, made with VHB 4910 as the dielectric and electrodes made of carbon grease.

The dielectric elastomer used in this documentation is VHB 4910 because it is a sticky tape which can adhere to the acrylic frame on its own. If other materials are used for the membrane, clamps or glue may be used to attach it to the frame.

Process Overview

The manufacturing process can be divided into the following steps:

1. Prestretching of the membrane onto the rigid frame.

2. Painting of the active area with carbon grease.

3. Application of copper leads.

4. Connecting active area with copper tapes.

Get Started

First visit the Bill of Materials page to make sure you have the necessary materials and then continue on to Step 1 to begin building your own actuator!

Bill of Materials

Materials


VHB 4910** (Supplier link)	Acrylic to make frame (Supplier link)

Carbon grease (Supplier link)	Copper tape (Supplier link)

** use red backing to make stencils for prestretching and active area. This material doesn't stick to the VHB so it is very easy to work with.

Tools


Pen	Scissors

Cotton Swabs (Q-Tips work fine)	Plastic Cup

Gloves	Disposable underlay

High Voltage Amplifier (Supplier link)	Voltage source (signal generator if possible)

Pre-step: Make stencils and frame

The circular actuator fabricated in this documentation uses an equibiaxial prestretch of 3 (i.e. the membrane is stretched three times equally in all directions). In order to achieve this prestretch, the acrylic frame and the initial piece of VHB must have the correct dimension ratio (3:1). The important dimensions to consider are the outside diameter of the acrylic frame and the outer diameter of the stencil used to cutout the initial piece of VHB.

We make the rigid frame out of acrylic so that it can be reused multiple times. The VHB can be simply peeled off and the frame washed in order to use it again. The two stencils are made using the red cover foil that is attached to VHB 4910 when it is sold from 3M, because it does not stick to VHB and therefore does not damage it upon removal.

	The acrylic frame used in this documentation has an outer diameter of 6 inches and an inner diameter of 5 inches. The frame can be made using a laser cutter. The .DXF file should have two concentric circles of the given dimensions. You can also use 15 cm and 13 cm for outer and inner diameter dimensions respectively.
	The first stencil is a circle with outer diameter equal to 1/3 of the outer diameter of the acrylic frame you make. In our case, the stencil will be 2 inches in diameter or 5 cm.
	The stencil used when painting the active area has outer diameter equal to the inner diameter of the acrylic frame. In this example, that would be 5 inches or 13 cm. The inner diameter can be whatever you want it to be, but in this example it is 1.5 inches or 3.75 cm. This stencil can be also be laser cut or simply drawn and cut out with scissors.

Step 1: Prestretching

Make sure to start with a clean working area. It is not necessary to have a perfectly clean actuator, but dust and debris can damage the membrane, leading to a failed actuator.

Do not use gloves for this step. The VHB sticks to the glove material and makes working with it difficult.

	Cut a square of VHB slightly larger than the stencil area Place the VHB with the red side facing down (sticky side up) Draw the outline of the stencil onto the VHB 4910 in pen. Stray pen marks outside the circle are fine. Some pens use an ink which dissolves VHB 4910 and leads to rupture during the prestretching process. The exact types of pens are not known, but generally low-end ball point pens should work.
	Cut out the stencil This does not need to be perfectly cut out. A little area of tape outside the drawn circle makes attaching to the frame easier. Pay careful attention to not notch the outer edge. This can cause the material to tear when it is actuated. Remove the red backing material from the VHB tape. A good way to remove the backing is to stretch the tape parallel to the surface to separate a small section and then pull perpendicularly (as seen in video below).

Next, attach the membrane on four opposite points to the acrylic ring, such that the inside of the drawn line aligns with the outer edge of the ring.
Attach the membrane in between each of the four attached points to the ring, such that there are eight equally spaced attachment points along the ring.
Go Slow! Rushing the prestretching step can result in torn actuators, which will need to be redone.

	Now, go along the ring and attach the whole membrane to the ring. Align the membrane such that the inside of the drawn line aligns with the outer edge of the acrylic frame. If the membrane was not perfectly aligned when first attached, gently remove the section and reattach in correct alignment (as seen in video on left).

Step 2: Paint Active Area

Working with Carbon Grease

Carbon grease is a material that quickly contaminates the whole workspace including clothes and shoes. Always wear gloves as soon as carbon grease is applied to the membrane and use a disposable underlay. If you value the clothing you are wearing, immediately change a glove if it becomes dirty in order to avoid any further contamination.

Before painting, put some of the carbon grease from the tube into a plastic cup for easier handling.

Painting the active area

	Attach the stencil for the active area to one side of the membrane. The stencil can be seen through the membrane. It can be helpful to leave a small section of the stencil loose for easier removal later.
	Carefully paint the area on the opposite side of the membrane using a thick layer of carbon grease. This way the stencil can be reused. Stay within the boundaries of the stencil. If a small amount of carbon grease gets outside the painted area, you can paint the leads through that area as described in this section.
	If multiple spots of carbon grease escape the active area, that actuator should be thrown away. Hold the actuator up to a light source. Light will show through in any spots not covered. Fill in any areas that present themselves.
	After the first side is painted, remove the stencil and paint a thick layer of carbon grease on the second side so it matches the previously painted area. Make sure the entire area is covered by grease.
	Stay within the boundaries of the previously painted area. A small amount of carbon grease escaped the active area in the video on the left, but it was not significant enough to redo the actuator.

Save any leftover carbon grease and cotton swabs for step 4.

Step 3: Attach Copper Tape

In this step, short pieces of copper tape are attached on opposing sides of the active layer. The copper tape is folded over to allow attachment a high voltage amplifier later.

Fixing mistakes from Step 2

If some stray carbon grease found its way outside the active area during Step 2, simply choose that direction to attach the copper tape. Draw an imaginary line from the active area through the mistake and attach a strip of copper tape where that line intersects with the frame. A line of carbon grease will be painted right over the mistake in Step 4, covering it up.

	Cut a strip of copper tape around 4" in length. Cut the strip in half lengthwise producing two thin strips. The width of the copper tape will depend on the size of your actuator. In this example, 1/2" wide copper tape is a good size.
	Attach one of the strips to the side of the actuator where the membrane lies flat on the frame (the topside). The copper tape will stick to the VHB so no glue needs to be used. Start by attaching the copper strip so that it extends into the membrane area inside the frame.
	Then fold the copper strip and attach the other end to the underside of the actuator frame (not the membrane area inside the frame). Do not pull on the membrane when attaching the copper strips.

	Attach the other strip to the underside of the actuator. To easily attach the strip over the lip of the frame, create a "foot" with the end of the copper tape.
	This second strip must be connected on the opposite side from the first strip. If it is not, when the active area is connected to the copper strips with carbon grease, the connected area will be active (which we don't want).
	The actuator should look like the image on the left when both copper strips are attached.

Step 4: Connect Active Areas to Leads

The last step involves connecting the active areas to the copper tape attached in the previous step.

	Using the remaining carbon grease, draw a line of carbon grease from one active area to a strip of copper tape. Connect the active area to the strip which is connected to the same side of the membrane. The carbon grease does not need to fully cover the copper tape, but a generous contact area will guarantee good conductivity.
	Flip the actuator over and paint a line from the active area to the copper strip attached on this side.