Electrical conductivity and Young’s modulus of flexible nanocomposites made by metal-ion implantation of polydimethylsiloxane: The relationship between nanostructure and macroscopic properties

Abstract

The mechanical and electrical properties of nanocomposites created by gold and titanium implantation into polydimethysiloxane (PDMS) are reported for doses from 10 15 to 5 Â 10 16 at. cm À2, and for ion energies of 2.5, 5 and 10 keV. Transmission electron microscopy (TEM) cross-section micrographs allowed detailed microstructural analysis of the implanted layers. Gold ions penetrate up to 30 nm and form crystalline nanoparticles whose size increases with ion dose and energy. Titanium forms a nearly homogeneous amorphous composite with the PDMS up to 18 nm thick. Using TEM micrographs, the metal volume fraction of the composite was accurately determined, allowing both electrical conductivity and Young's modulus to be plotted vs. the volume fraction, enabling quantitative use of percolation theory for nanocomposites <30 nm thick. This allows the composite's Young's modulus and conductivity to be linked directly to the implantation parameters and volume fraction. Electrical and mechanical properties were measured on the same nanocomposite samples, and different percolation thresholds and exponents were found, showing that, while percolation explains both conduction and stiffness of the composite very well, the interaction between metal nanoparticles occurs differently in determining mechanical and electrical properties.

Microfabrication and characterization of an array of dielectric elastomer actuators generating uniaxial strain to stretch individual cells

“…This leads to nm-sized gold clusters in the top 50 nm of the PDMS surface that creates a conductive path sustaining up to 175% uniaxial stretch before break [14,15]. Increasing the gold dose not only increases the conductivity, but also increases the stiffness of the gold-PDMS composite.…”

“…The electrodes are patternable in μm-scale and present a low surface resistance (<1 k per square); they can be stretched up to 175% strain and survive more than 100 000 cyclic deformations to 30% strain. Crucially, the ion-implanted electrodes have a low impact on Young's modulus of the elastomer on which they are patterned (40% relative increase) thanks to the formation of a gold-PDMS nanocomposite [14,15].…”

Ion implanted dielectric elastomer circuits

“…In FCVA metal ion implantation, metal plasma is created by a high voltage discharge in a vacuum (Fig. 4) [28]. The content of the beam is filtered to remove big, heavy macro particles using a curved magnetic field-leaving only gold ions which are electrostatically accelerated to several keV to embed in a sample.…”

“…These effects all contribute to varying dose per pulse or varying shape between pulses and are difficult to control. The best approach is to hold as many parameters constant between jobs, record data to establish trends, raster in a pattern to distribute any change in the dose per pulse across the device and control [28] showing a strong percolation threshold the process with a single parameter. The control parameter we chose was pulses/cm 2 , which is the number of times the implanter fires a packet of gold ions at the substrate for a given area.…”

“…[20,27]) stretchable electrode. FCVA gold ion implantation has been used to make stretchable electrodes for DEA in a range of applications including steerable mirrors, living cell stretchers, and microfluidic devices [28][29][30][31][32].…”