Large strain deformation and cracking of nano-scale gold films on PDMS substrate

Akogwu, Onobu; Kwabi, David G.; Midturi, Swaminadham; Eleruja, Marcus Adebola; Babatope, Babaniyi; Soboyejo, W. O.

doi:10.1016/j.mseb.2010.02.023

Cited by 45 publications

(37 citation statements)

References 23 publications

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“…18,19,25,26 Furthermore, Cu films on polyimide show severe cracking at strains above $20%, even when strongly bonded to the substrate. 27 Thin Au films on elastomers have been stretched in excess of 20% when the metal-substrate interface is intact, [28][29][30][31] but for many applications Au is prohibitively expensive. In general, thin films on elastomers may be stretched somewhat beyond their bulk counterparts due to suppression of necking instability.…”

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confidence: 99%

Super-stretchable metallic interconnects on polymer with a linear strain of up to 100%

Arafat

Dutta

Panat

2015

Applied Physics Letters

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Metal interconnects in flexible and wearable devices are heterogeneous metal-polymer systems that are expected to sustain large deformation without failure. The principal strategy to make strain tolerant interconnect lines on flexible substrates has comprised of creating serpentine structures of metal films with either in-plane or out-of-plane waves, using porous substrates, or using highly ductile materials such as gold. The wavy and helical serpentine patterns preclude high-density packing of interconnect lines on devices, while ductile materials such as Au are cost prohibitive for real world applications. Ductile copper films can be stretched if bonded to the substrate, but show high level of cracking beyond few tens of % strain. In this paper, we demonstrate a material system consisting of Indium metal film over an elastomer (PDMS) with a discontinuous Cr layer such that the metal interconnect can be stretched to extremely high linear strain (up to 100%) without any visible cracks. Such linear strain in metal interconnects exceeds that reported in literature and is obtained without the use of any geometrical manipulations or porous substrates. Systematic experimentation is carried out to explain the mechanisms that allow the Indium film to sustain the high strain level without failure. The islands forming the discontinuous Cr layer are shown to move apart from each other during stretching without delamination, providing strong adhesion to the Indium film while accommodating the large strain in the system. The Indium film is shown to form surface wrinkles upon release from the large strain, confirming its strong adhesion to PDMS. A model is proposed based upon the observations that can explain the high level of stretch-ability of the Indium metal film over the PDMS substrate. V C 2015 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4929605] The proliferation of 'smart' wearable devices is predicted to lead to the "Internet of Things" (IoT) revolution over the next two decades. The examples of such devices include flexible displays, 1-4 robotic skin, 5 stretchable circuits, 6 hemispherical electronic eye, 7 epidermal electronics, 8 cardiac sensors, and diagnostic contact lens. 9 Flexible electronic platforms typically require that its components be connected with each other on a flexible substrate using metallic interconnects. The design and manufacturing of such interconnects that have high spatial density and can be reliably stretched to large strains has become one of the most critical challenges for the IoT revolution. The essential requirements for the interconnect system include strain compatibility of components at the interfaces, minimal increase in resistivity under stretching, and recovery of the resistivity once the strain is released. In addition, any geometrical manipulation to accommodate deformation must be compatible with the interconnect density demanded by the industry. 10,11 The current methods to improve interconnect stretch-ability include creating serpentine structures of metal films 12-2...

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confidence: 99%

Super-stretchable metallic interconnects on polymer with a linear strain of up to 100%

Arafat

Dutta

Panat

2015

Applied Physics Letters

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“…International collaborations among the United States and Africa, [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42] J oint US-Africa Materials Institute (JUAMI) will be held December 10-21, 2018, in Kampala, Uganda. JUAMI features tutorials on cutting-edge energy materials topics, hands-on experiments and learning activities, and research seminars.…”

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confidence: 99%

Strengthening diversity and cooperation through international collaborations: A focus on Africa, South America, and the Caribbean

Soboyejo

Madsen

2018

MRS Bull.

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Africa is the second largest continent in terms of size and population.1,2 With approximately 1.256 billion people (about 15% of the world’s population) and a land area of 30.3 million square kilometers (including adjacent islands), it occupies about 20.4% of the earth’s total land area.1 A significant fraction of the people in the Caribbean* and South America are of African descent, and there are many historical and cultural links among the people of these regions.3 South America has 422.5 million people, and the Caribbean has about 39.12 million people;1 hence, the total population of all three areas represents about 20% of the world’s population.1,2 Similarities in climate also mean that common approaches can be explored for establishing sustainable building materials, and the range of development indices offer unique opportunities for collaborations in research and education that can facilitate human development.4

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“…The resistivity difference between Pt and Au was much larger for thin films than their corresponding bulks. Comparisons of the resistance-change behaviors of Pt and Au thin films clearly reveals that Au metallization is more suitable to utilize as stretchable interconnects and electrodes than Pt thin film [13][14][15][28][29][30]. …”

Section: Figurementioning

confidence: 99%

Formation of metal interconnects and their resistance-change behavior during tensile stretching for stretchable packaging applications

Park

Han

et al. 2016

2016 Pan Pacific Microelectronics Symposium (Pan Pacific)

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We examined the resistance-change behavior of thin Pt and Au films on the PDMS elastomeric substrate. A maximum Young's modulus of 1.74 MPa was obtained for the PDMS substrate by adjusting the mixing ratio between base polymer and its curing agent to 10:1. Parylene coating on the PDMS surface was effective as an adhesion layer between metal interconnects and PDMS substrate. Without a Parylene coating, the resistance of a 150 nm-thick Pt film increased from 18.7to 3000 with stretching to 20% strain and became open at strains larger than 20%. On the other hand, the resistance of a Pt film, sputtered on a Parylene-treated PDMS, was initially 10.3 before loading, increased to 99.3 at 30% elongation, and then decreased to 23.8 after complete unloading. Thin Au metallization has better resistance properties for stretchable interconnect applications than Pt thin film. The resistance of a 150 nmthick Au film on a Parylene-coated PDMS substrate was 1.3 before loading, increased to 19 at 30% elongation, and then returned to 1.3 after complete unloading.

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Large strain deformation and cracking of nano-scale gold films on PDMS substrate

Cited by 45 publications

References 23 publications

Super-stretchable metallic interconnects on polymer with a linear strain of up to 100%

Super-stretchable metallic interconnects on polymer with a linear strain of up to 100%

Strengthening diversity and cooperation through international collaborations: A focus on Africa, South America, and the Caribbean

Formation of metal interconnects and their resistance-change behavior during tensile stretching for stretchable packaging applications

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