#  Step 1: Prestretching 

 



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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.

Sort   ![draw_stencil_outline.jpg](/sites/g/files/omnuum4601/files/styles/hwp_1_1__360x360_scale/public/sorotoolkit/files/draw_stencil_outline.jpg?itok=FQso_W0r) 

 



- 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_stencil_out.jpg](/sites/g/files/omnuum4601/files/styles/hwp_1_1__360x360_scale/public/sorotoolkit/files/cut_stencil_out.jpg?itok=NSGJ8N1s) 

 



- 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).



   ![remove_backing.jpg](/sites/g/files/omnuum4601/files/styles/hwp_1_1__360x360_scale/public/sorotoolkit/files/remove_backing.jpg?itok=N7SeTX6B) 

 





 







Sort   ![4_corners.png](/sites/g/files/omnuum4601/files/styles/hwp_1_1__360x360_scale/public/sorotoolkit/files/4_corners.png?itok=caxMIQHg) 

 



- 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.



   ![8_corners.png](/sites/g/files/omnuum4601/files/styles/hwp_1_1__360x360_scale/public/sorotoolkit/files/8_corners.png?itok=Nem92GwU) 

 





 





 



- 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).







### Bibliography

Keplinger et al. (2012) [Harnessing snap-through instability in soft dielectrics to achieve giant voltage-triggered deformation.](/publications/harnessing-snap-through-instability-soft-dielectrics-achieve-giant-voltage)

Keplinger et al. (2013) [Stretchable, transparent, ionic conductors.](/publications/stretchable-transparent-ionic-conductors)

Koh et al. (2009) [Maximal energy that can be converted by a dielectric elastomer generator.](/publications/maximal-energy-can-be-converted-dielectric-elastomer-generator)

Wissler and Mazza (2007) [Mechanical behavior of an acrylic elastomer used in dielectric elastomer actuators.](/publications/mechanical-behavior-acrylic-elastomer-used-dielectric-elastomer-actuators)

Pelrine et al. (2001) [Dielectric elastomers: generator mode fundamentals and applications.](/publications/dielectric-elastomers-generator-mode-fundamental-and-applications)

Pelrine et al. (2000) [High-Speed Electrically Actuated Elastomers with Strain Greater Than 100%.](https://softroboticstoolkit.com/sorotoolkit/publications/high-speed-electrically-actuated-elastomers-strain-greater-100)

Röntgen WC. (1880) [Ueber die durch Electricität bewirkten Form—und Volumenänderungen von dielectrischen Körpern.](/publications/ueber-die-durch-electricitat-bewirkten-form%E2%80%94und-volumenanderungen-von)

Suo, Zhigang (2010) [Theory of dielectric elastomers.](/publications/theory-dielectric-elastomers)

### Contributors

Philipp Rothemund