Mechanical properties of silicones for MEMS

We present experimental results on a model system for studying wave propagation in a complex medium exhibiting low frequency resonances. These experiments enable us to investigate a fundamental question that is relevant for many materials, such as metamaterials, where low-frequency scattering resonances strongly influence the effective medium properties. This question concerns the effect of correlations in the positions of the scatterers on the coupling between their resonances, and hence on wave transport through the medium. To examine this question experimentally, we measure the effective medium wave number of acoustic waves in a sample made of bubbles embedded in an elastic matrix over a frequency range that includes the resonance frequency of the bubbles. The effective medium is highly dispersive, showing peaks in the attenuation and the phase velocity as functions of the frequency, which cannot be accurately described using the Independent Scattering Approximation (ISA). This discrepancy may be explained by the effects of the positional correlations of the scatterers, which we show to be dependent on the size of the scatterers. We propose a self-consistent approach for taking this "polydisperse correlation" into account and show that our model better describes the experimental results than the ISA.

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“…The stationary limit (f = 0 MHz) of our estimate of µ ′ is in good agreement with the value reported in the literature [21].…”

Section: B Sample Characterizationsupporting

confidence: 92%

Influence of positional correlations on the propagation of waves in a complex medium with polydisperse resonant scatterers

et al. 2011

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“…More complex, irregular designs might be required in many cases of practical importance; these can also be implemented in noncoplanar mesh designs. We demonstrated this concept for a differential amplifier (10), in which we divided the circuit into 4 sections, each of which forms an island connected by metal lines on pop-up bridges. The red dotted boxes in Fig.…”

Section: Resultsmentioning

confidence: 99%

Materials and noncoplanar mesh designs for integrated circuits with linear elastic responses to extreme mechanical deformations

Kim

Song

Choi

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

647

474

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Electronic systems that offer elastic mechanical responses to highstrain deformations are of growing interest because of their ability to enable new biomedical devices and other applications whose requirements are impossible to satisfy with conventional wafer-based technologies or even with those that offer simple bendability. This article introduces materials and mechanical design strategies for classes of electronic circuits that offer extremely high stretchability, enabling them to accommodate even demanding configurations such as corkscrew twists with tight pitch (e.g., 90°in Ϸ1 cm) and linear stretching to ''rubber-band'' levels of strain (e.g., up to Ϸ140%). The use of single crystalline silicon nanomaterials for the semiconductor provides performance in stretchable complementary metal-oxide-semiconductor (CMOS) integrated circuits approaching that of conventional devices with comparable feature sizes formed on silicon wafers. Comprehensive theoretical studies of the mechanics reveal the way in which the structural designs enable these extreme mechanical properties without fracturing the intrinsically brittle active materials or even inducing significant changes in their electrical properties. The results, as demonstrated through electrical measurements of arrays of transistors, CMOS inverters, ring oscillators, and differential amplifiers, suggest a valuable route to high-performance stretchable electronics.flexible electronics ͉ stretchable electronics ͉ semiconductor nanomaterials ͉ plastic electronics ͉ buckling mechanics I ncreasingly important classes of application exist for electronic systems that cannot be formed in the usual way, on semiconductor wafers. The most prominent example is in large-area electronics (e.g., back planes for liquid crystal displays), where overall system size rather than operating speed or integration density, is the most important metric. Similar systems that use flexible substrates are presently the subject of widespread research and commercialization efforts because of advantages that they offer in durability, weight, and ease of transport/use (1, 2). Stretchable electronics represents a fundamentally different and even more challenging technology, of interest for its unique ability to flex and conform to complex curvilinear surfaces such as those of the human body. Several promising approaches exist, ranging from the use of stretchable interconnects between rigid amorphous silicon devices (3) to ''wavy'' layouts in singlecrystalline silicon CMOS circuits (4), both on elastomeric substrates, to net-shaped structures in organic electronics on plastic sheets (5). None offers, however, the combination of electrical performance (high electron and hole mobility), scalability (with relatively modest modifications to conventional microelectronic technologies), integrated circuit applicability in complementary designs and mechanical properties required of some of the most demanding, and most interesting, systems. Here, we introduce design concepts for stretchable electronics th...

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“…VanLandingham et al 2005;White et al 2005;Choi et al 2008;Lin et al 2008;Schneider et al 2008). However, Perutz et al (1998) noted that PDMS networks at room temperature are well above their glass transition temperature (T g ∼ −120…”

Section: Experimental Testing Of Adhesion and Tangential Loading Usinmentioning

confidence: 99%

Mode-mixity-dependent adhesive contact of a sphere on a plane surface

2009

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Tangential loading in the presence of adhesion is highly relevant to biological locomotion, but mixed-mode contact of biological materials or similar soft elastomers remains to be well understood. To better capture the effects of dissipation in such contact problems owing to viscoelasticity or irreversible interfacial adhesive processes, a model is developed for the combined adhesive and tangential loading of a rigid sphere on a flat halfspace which incorporates a phenomenological model of energy dissipation in the form of increased effective work of adhesion with increasing degree of mode mixity. To verify the model, contact experiments are performed on polydimethylsiloxane (PDMS) samples using a custom-built microtribometer. Measurements of contact area during mixed normal/tangential loading indicate that the strong dependence of the effective work of adhesion upon mode mixity can be captured effectively by the phenomenological model in the regime where the contact area stayed circular and the slip was negligible. Rate effects were seen to be described by a power-law dependence upon the crack front velocity, similar to observations of rate-dependent contact seen for pure normal loading.

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Mechanical properties of silicones for MEMS

Cited by 372 publications

References 40 publications

Influence of positional correlations on the propagation of waves in a complex medium with polydisperse resonant scatterers

Influence of positional correlations on the propagation of waves in a complex medium with polydisperse resonant scatterers

Materials and noncoplanar mesh designs for integrated circuits with linear elastic responses to extreme mechanical deformations

Mode-mixity-dependent adhesive contact of a sphere on a plane surface

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