Silicone membrane production ‒ LMTS ‐ EPFL

Why silicone?

Dielectric Elastomer Actuators (DEAs) consists of a thin layer of elastomer sandwiched between two compliant electrodes. Different classes of elastomer materials have been used as soft membranes to manufacture DEAs:

Acrylic elastomer (adhesive film VHB produced by 3M)
Silicone elastomers
Polyurethanes

The acrylic elastomer VHB is the most widely used elastomer to make DEAs (~3/4 of the published results are obtained with VHB) for two main reasons

VHB-based actuators exhibit larger strain than similar actuator made with silicone.
However, because it is mechanically very lossy, the strain of VHB actuators decreases sharply with actuation frequency. For driving frequencies over 0.1Hz, silicone elastomers show larger actuation strain
VHB can be readily bought in film form, removing the need to prepare membrane

At the EPFL-LMTS, we work with silicone elastomers as membrane for DEAs. In general, silicones exhibit much better mechanical characteristics than VHB, leading to very fast actuators with a bandwidth 3 orders of magnitude higher than VHB.

The need to cast silicone membranes (unlike VHB, which can be bought in film) requires additional processing steps,which can be seen as a disadvantage. However, it provides additional design freedom, such as the possibility to cast films at any desired thickness, or to choose between silicones with different properties.

Silicone membranes can be cast on large surfaces quite easily and rapidly, and the following sections describe our fabrication process.

Silicone membrane casting

To produce high quality silicone membranes, we use the blade casting method, which allows producing large area membranes with homogenous thickness in a short amount of time.

We use a universal applicator with adjustable gap in combination with an automated film coater. The casting is done on high quality PET sheets with a very low surface roughness (Melinex ST-506)

1) Sacrificial layer coating

We start by applying a water-soluble sacrificial layer on the casting substrate in order to ease the separation of the membrane from the PET substrate, and to avoid having to pull too hard on the membrane to remove it from the sheet. Deforming the membrane during the release step can lead to anisotropic mechanical properties because of the Mullins effect, and should be avoided.

For the sacrificial layer, we use a 5% wt solution of Poly(acrylic acid) (PAA) in isopropanol, that we coat with to a wet thickness of about 20 um. Once coated, the isopropanol evaporates quickly, leaving a dry layer of PAA of about 1um.

2) Silicone membrane casting

Once the sacrificial layer has dried, the same coating equipment can be used to cast the silicone layer. The two components of the silicone are mixed according the manufacturer’s specifications in a planetary mixer. Depending on the viscosity of the silicone components, solvent can also be added to reduce the viscosity of the mixture.

After mixing, the silicone/solvent mixture is placed in front of the applicator, and the machine is started at a speed of 1-5mm/s. Once the coating is completed, the PET substrate is removed from the film coater and placed in an oven at 80°C for about 30 minutes for the cross-linking of the silicone.

We then have a cured silicone layer of 200x300mm² with a thickness between 5 and 100 um, depending on the gap of the applicator

3) Membrane release

Because we are mainly working with small-size DEAs, we can produce many actuators from one sheet of silicone membrane. The next step of our process consists in cutting the silicone sheet into smaller parts, and releasing the silicone layer from the PET substrate in order to obtain freestanding silicone membranes.

The membrane sheet is cut into circles of 55mm of diameter (picture above, left) with a CO₂ Laser engraver (Speedy 300). In parallel, prestretching frames are cut in a PET foil laminated with dry silicone adhesive (picture above, right. Black lines have been printed on the PET foil for better contrast on the pictures). The frames help for the manipulation of the membranes during the release and prestretch steps.

Each membrane circle is then applied on one of the prestretch frame, with the adhesive of the frame in contact with the silicone membrane.

The assembly is dipped into hot water, which dissolves the sacrificial layer. It is then possible to easily peel the PET substrate away, without inducing any deformation in the thin silicone membrane. After this step, we end up with free-standing silicone membranes fixed to the teeth of the prestretch frame.

4) Membrane prestretch

We show here equi-biaxial prestretching of a membrane fixed on a prestretch frame

The prestretch adhesive frame holdind the thin suspended silicone membrane is placed on our circular equi-biaxial stretcher. Each of the teeth of the frame is aligned with a finger of the stretcher. The adhesive of the frame makes it stick to the fingers of the stretcher. A scisor is then used to cut the adhesive prestretch frame in between the fingers of the stretcher.

The fingers of the stretcher are then retracted, causing an increase of the membrane diameter (equi-biaxial stretching)

Finally a frame covered with silicone dry adhesive is stuck on the membrane. The excess of membrane around the frame is cut. At this stage, a cicular frame with a prestretched silicone membrane is obtained. The fabrication process can then continue with the application of the compliant electrodes.

Publications on the membrane production process

Field Guide to Northern Tree-related Microhabitats: Descriptions and size limits for their inventory in boreal and hemiboreal forests of Europe and North America

R. Bütler Sauvain; L. Larrieu; L. F. Lunde; M. Maxence; B. Nordén et al.

Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Switzerland, 2024.

Why silicone?

Silicone membrane casting

1) Sacrificial layer coating

2) Silicone membrane casting

3) Membrane release

4) Membrane prestretch

Publications on the membrane production process

Field Guide to Northern Tree-related Microhabitats: Descriptions and size limits for their inventory in boreal and hemiboreal forests of Europe and North America

Data Champions Lunch Talks – Green Bytes: Data-Driven Approaches to EPFL Sustainability

Comparison of Three Viral Nucleic Acid Preamplification Pipelines for Sewage Viral Metagenomics

How to Support Students to Develop Skills that Promote Sustainability

How to Support Students Giving Each Other Constructive Feedback, Especially When It Is Difficult to Hear

How teachers can use the 3T PLAY trident framework to design an activity that develops transversal skills

The conceptual foundations of innate immunity: Taking stock 30 years later

Radio-Activities: Architecture and Broadcasting in Cold War Berlin

No Last One

All That is Solid

Characterization of the gut-bone marrow axis through bile acid signaling

Studies of crystal collimation for heavy ion operation at the LHC

Engineering novel protein interactions with therapeutic potential using deep learning-guided surface design

Querying the Digital Archive of Science: Distant Reading, Semantic Modelling and Representation of Knowledge

Hybrid organic/metal-oxide shells on semiconductor nanocrystals via colloidal atomic layer deposition

Electrical and Optical Manifestations of Flat Band Physics in Van der Waals Materials

Plasmonically enhanced molecular junctions for investigation of atomic-scale fluctuations in self-assembled monolayers

Exact Obstacle Avoidance for Robots in Complex and Dynamic Environments Using Local Modulation

S-acylation and lipid exchange at the ER-Golgi membrane contact sites regulate pathogen entry in human cells

Serial Dependence in Human Visual Perception and Decision-Making

Data-Driven Methods for Controller Design in Atomic Force Microscopy

Quantum-mechanical effects in photoluminescence from thin crystalline gold films

Quantifying the effects of rainfall temporal variability on landscape evolution processes

Towards a metabolic theory of catchments: scaling of water and carbon fluxes with size

Biohybrid Superorganisms—On the Design of a Robotic System for Thermal Interactions With Honeybee Colonies

Dataset to accompany publication “Quantum-mechanical effects in photoluminescence from thin crystalline gold films”

Impact of CO2-rich seawater injection on the flow properties of basalts

Architecture of a decentralised decision support system for futuristic beehives

TSLAM: a tag-based object-centered monocular navigation system for augmented manual woodworking.

Water weakening and the compressive brittle strength of carbonates: Influence of fracture toughness and static friction

Integration of the Pilatus3 detector for soft X-ray diagnostics on TCV

Siloxide tripodal ligands as a scaffold for stabilizing lanthanides in the +4 oxidation state

High-Permittivity Polysiloxanes for Bright, Stretchable Electroluminescent Devices

An extension of the stochastic sewing lemma and applications to fractional stochastic calculus

A bridge between trust and control: computational workflows meet automated battery cycling

Capsizing due to friction-induced twist in the failure of stopper knots

A CTCF-dependent mechanism underlies the Hox timer relation to a segmented body plan

Gradient High-Q Dielectric Metasurfaces for Broadband Sensing and Control of Vibrational Light-Matter Coupling

SOMOphilic alkyne vs radical-polar crossover approaches: The full story of the azido-alkynylation of alkenes

Dielectric elastomer actuator-based valveless pump as Fontan failure assist device: introduction and preliminary study

Tree diversity reduces variability in sapling survival under drought

Probing structural and dynamic properties of MAPbCl3 hybrid perovskite using Mn2+ EPR

Benchmarking machine-readable vectors of chemical reactions on computed activation barriers

Quantum radio astronomy: Data encodings and quantum image processing

Comprehensive Memory Safety Validation: An Alternative Approach to Memory Safety

A Method of Moments Estimator for Interacting Particle Systems and their Mean Field Limit

A setup for hard x-ray time-resolved resonant inelastic x-ray scattering at SwissFEL

An aircraft assembly process formalism and verification method based on semantic modeling and MBSE

Stellar Metallicities and Gradients in the Isolated, Quenched Low-mass Galaxy Tucana

Twisted pair transmission line coil – a flexible, self-decoupled and robust element for 7 T MRI

3D Printing of Double Network Granular Elastomers with Locally Varying Mechanical Properties

Dopant-additive synergism enhances perovskite solar modules

Proliferation-driven mechanical compression induces signalling centre formation during mammalian organ development

Spin-Reorientation-Driven Linear Magnetoelectric Effect in Topological Antiferromagnet Cu3TeO6

Is There a Special Role for Ovarian Hormones in the Pathogenesis of Lobular Carcinoma?

Stick-slip-to-stick transition of liquid oscillations in a U-shaped tube

Opportunities and challenges in design and optimization of protein function

Impact of beam-coupling impedance on the Schottky spectrum of bunched beam

Gaussian universality of perceptrons with random labels

Diffusion of brain metabolites highlights altered brain microstructure in type C hepatic encephalopathy: a 9.4 T preliminary study

Teaching about non-deterministic physics: an almost forgotten fundamental contribution of Marie Curie

The angiogenic growth of cities

Learning Weakly Convex Regularizers for Convergent Image-Reconstruction Algorithms

Euclid: Improving the efficiency of weak lensing shear bias calibration

Randomized flexible GMRES with deflated restarting

An interior penalty coupling strategy for isogeometric non-conformal Kirchhoff-Love shell patches

Stress tolerance of lightweight glass-free PV modules for vehicle integration

On the Arithmetic and Geometric Fusion of Beliefs for Distributed Inference

Alpha1-antitrypsin improves survival in murine abdominal sepsis model by decreasing inflammation and sequestration of free heme

Quantitative prediction of crystallization in laser powder bed fusion of a Zr-based bulk metallic glass with high oxygen content

A cut-cell method for the numerical simulation of 3D multiphase flows with strong interfacial effects

Speciation of Lanthanide Metal Ion Dopants in Microcrystalline All-Inorganic Halide Perovskite CsPbCl3

Can Gas Consumption Data Improve the Performance of Electricity Theft Detection?