Fabrication of zipping electrostatic actuators incorporating inkjet-printed layers

Zipping electrostatic actuators operate by bending flexible electrodes using electrostatic forces. This principle allows the use of a wide range of dielectric and conductive materials. Additive Manufacturing (AM) techniques can be used to fabricate these actuators. The selective direct deposition of multiple materials improves the actuator design flexibility, as customized prototypes can be fabricated without masks and moulds. Here we present the first integration of AM techniques in the fabrication process of Hydraulically Amplified Taxels (HAXELs), a class of electrostatic actuators combining zipping electrodes deformation with the inflation of a stretchable material using fluidic coupling. We use an inkjet printer (jetlab (R) 4 by MicroFab) to deposit Polydimethylsiloxane (PDMS) as the stretchable material and Ethyl Cellulose as a sacrificial material for fluidic features patterning. We integrate gold-sputtered, laser-cut Mylar foils for the flexible part of the actuator by encapsulating them between the inkjet-printed layers. After dissolving the sacrificial material, a dielectric fluid can be injected in the fabricated actuators. Qualitative evaluation of a fabricated device is reported, showing electrode zipping. The presented fabrication process allows future fabrication of highly integrated actuators having arbitrary shapes.

Through Silicon Vias and thermocompression bonding using inkjet-printed gold nanoparticles for heterogeneous MEMS integration

Niels Quack

We present a novel technique for heterogeneous integration using gold filled Through Silicon Vias (TSV) and thermocompression bond bumps formed in a single fabrication step, using gold nanoparticles dispensed by inkjet printing. Gold-filled TSV arrays (12 × 12, via radius 50μm, pitch 250μm) have been demonstrated using this method. Void free, filled TSVs are reported, and thermocompression bonding yielded seamless interfaces. Die shear tests show good bond strength, and sub-Ω via resistances were measured. The presented integration process exhibits a low temperature budget (≤250°C), allows good alignment, and is compatible with substrates of different sizes and materials, enabling the heterogeneous integration of known-good-dies (KGD) which may have been fabricated in different technologies.

IEEE2013

High-cycle electromechanical aging of dielectric elastomer actuators with carbon-based electrodes

Christine Anne de Saint-Aubin, Samuel Rosset, Samuel Schlatter, Herbert Shea

We present high-cycle aging tests of Dielectric Elastomer Actuators (DEAs) based on silicone elastomers, reporting on the time-evolution of actuation strain and of electrode resistance over millions of cycles. We compare several types of carbon-based electrodes, and for the first time show how the choice of electrode has a dramatic influence on DEA aging. An expanding circle DEA configuration is used, consisting of a commercial silicone membrane with the following electrodes: commercial carbon grease applied manually, solvent-diluted carbon grease applied by stamping (pad printing), loose carbon black powder applied manually, carbon black powder suspension applied by inkjet-printing, and conductive silicone-carbon composite applied by stamping. The silicone-based DEAs with manually applied carbon grease electrodes show the shortest lifetime of less than 10<sup>5</sup> cycles at 5% strain, while the inkjet-printed carbon powder and the stamped silicone-carbon composite make for the most reliable devices, with lifetimes greater than 10<sup>7</sup> cycles at 5% strain. These results are valid for the specific dielectric and electrode configurations that were tested: using other dielectrics or electrode formulations would lead to different lifetimes and failure modes. We find that aging (as seen in the change in resistance and in actuation strain vs. cycle number) is independent of the actuation frequency from 10 Hz to 200 Hz, and depends on the total accumulated time the DEA spends in an actuated state.

Institute of Physics2017

2D Material Based Inks For Room Temperature Printed Electronics

Sina Abdolhosseinzadeh

Functional printing is a versatile mass production method that has gained considerable scientific and industrial attention in the past few years. A wide range of electronics from passive circuit components (e.g., resistors and interconnects) to high-performance transistors and high-quality displays can now be printed energy-, resource-, and cost-efficiently. In spite of the recent progresses in the formulation of inks and significant reductions in their production costs, most of the commercially available inks are still very expensive (e.g., silver inks), and limited to a few conductive and insulator materials that usually require high-temperature thermal treatments to become fully functional. To enable new applications, and further reduce the production costs, it is necessary to develop novel inks based on semiconductive and new conductive materials (with improved chemical or optical properties) that can become functional after drying (dry-only inks). Development of such inks is very challenging, and the few successful results have been mostly obtained by polymer-based inks, which suffer from cost and chemical-stability issues.Since 2004 and after the first successful isolation of single-layer pristine graphene, 2D materials have disrupted almost all fields of science and technology, from medicine, to electronics and beyond. Their unique morphology, diverse and widely-tunable physical and chemical properties, ease of synthesis, low-cost of production, and abundance of raw materials have brought up new possibilities, which were not conceivable before. Formulation of additive-free inks for room-temperature printing of electronics is one of such possibilities. In spite of their great potential, formulation of additive-free 2D-material-based inks has so far been limited to low-concentration inks that are not suitable for high-throughput manufacturing, which is one of the main incentives for printing of electronics. Furthermore, current 2D materials' synthesis and processing methods have either low yield, or are not scalable, which further limit their real-world applications. Here in this work, several processing and ink formulation strategies are reported, which can address the aforementioned problems and pave the way towards out of lab application of 2D materials.In chapter 1, after a brief introduction on different device fabrication methods, basics of liquid-phase processing, especially the topics that are related to ink formulation and printing, are concisely reviewed. In chapter 2, a universal strategy for additive-free formulation of pristine 2D materials-based inks, and their scalable production are reported. Being a universal approach, this method allows us to print advanced electronic devices consisting different types of semiconductive and conductive materials. MXenes are a recently discovered group of 2D materials with exceptional optical and electronic properties which can revolutionize the printed electronics industry. Due to their importance and being at their early stages of discovery, 2 chapters of this thesis (chapters 3 & 4) have been dedicated to their ink formulation challenges. In chapter 3, the possibility of using byproducts of MXene synthesis as a sustainable ink formulation strategy has been investigated, which can simultaneously address the financial and environmental issues of printing electronics. In chapter 4, the conventional MXene ink formulation strategies are revisited to enable their scalable printing.

EPFL2021

2D Material Based Inks For Room Temperature Printed Electronics

Sina Abdolhosseinzadeh

EPFL2021