Fracture in Microscale SU-8 Polymer Thin Films

Das, Aditya Kumar; Sinha, Avick; Rao, V. Ramgopal; Jonnalagadda, Krishna

doi:10.1007/s11340-017-0262-6

Cited by 10 publications

(7 citation statements)

References 57 publications

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“…During in situ compression testing of these kirigami structures, the geometry was found to play a critical role in their flexibility and stretchability. Indeed, we found that structural design enables intrinsically stiff and brittle bulk materials such as Si and SU‐8 (≈2–3 and 10–12% tensile strain to fracture, respectively) to undergo large deformation . This results in an overall deformable and compliant structure, which can sustain large‐scale deformation, including twisting and bending.…”

Section: Comparison Between Kirigami Structures In Terms Of Response mentioning

confidence: 97%

Fabrication and Deformation of 3D Multilayered Kirigami Microstructures

Humood

Shi

Han

et al. 2018

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Mechanically guided 3D microassembly with controlled compressive buckling represents a promising emerging route to 3D mesostructures in a broad range of advanced materials, including single-crystalline silicon (Si), of direct relevance to microelectronic devices. During practical applications, the assembled 3D mesostructures and microdevices usually undergo external mechanical loading such as out-of-plane compression, which can induce damage in or failure of the structures/devices. Here, the mechanical responses of a few mechanically assembled 3D kirigami mesostructures under flat-punch compression are studied through combined experiment and finite element analyses. These 3D kirigami mesostructures consisting of a bilayer of Si and SU-8 epoxy are formed through integration of patterned 2D precursors with a prestretched elastomeric substrate at predefined bonding sites to allow controlled buckling that transforms them into desired 3D configurations. In situ scanning electron microscopy measurement enables detailed studies of the mechanical behavior of these structures. Analysis of the load-displacement curves allows the measurement of the effective stiffness and elastic recovery of various 3D structures. The compression experiments indicate distinct regimes in the compressive force/displacement curves and reveals different geometry-dependent deformation for the structures. Complementary computational modeling supports the experimental findings and further explains the geometry-dependent deformation.

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Section: Comparison Between Kirigami Structures In Terms Of Response mentioning

confidence: 97%

Fabrication and Deformation of 3D Multilayered Kirigami Microstructures

Humood

Shi

Han

et al. 2018

Small

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“…Their fracture energy (≈1500 J m −2 ) can be an order of magnitude higher than those of common polymers in electronics (e.g., SU-8), and it is comparable to that of natural rubber (Figure 2b). [30,31] The mechanical behaviors of CNFF can be further modified by tuning the concentrations of ANFs and PVA in the liquid precursor. A stretchable kirigami membrane from CNFF can bear loads ≈1000 times higher than its own weight without mechanical failure or propagation of the cuts (Figure 2c).…”

Section: Resultsmentioning

confidence: 99%

“…Specifically, with the same set of geometrical designs, the simulated energy release rates exceeded the intrinsic fracture energy of the constituent materials (e.g., ≈10 J m −2 for silicon or ≈107 J m −2 for SU-8) even at low levels of stretching (<10%) (Figure S4, Supporting Information), suggesting early onset of crack propagation and potential failure of the device. [31,34,35] Indeed, the driving force for fracture in kirigami structures is dependent on various parameters including the geometrical configuration of the cuts, the degree of imposed elongation, as well as the stiffness of the constituent materials, etc. Therefore, careful evaluation of specific designs with reference to the intrinsic fracture toughness of the constituent materials is important.…”

Section: Resultsmentioning

confidence: 99%

Robust and Multifunctional Kirigami Electronics with a Tough and Permeable Aramid Nanofiber Framework

Liu

Wang

et al. 2022

Advanced Materials

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components combine excellent electronic performance and good stretchability, [8,9] but their delicate structures are prone to mechanical damage. Transfer printing of serpentine electronics onto elastomer films could enhance their overall structural robustness. [10,11] However, the dense polymer substrate may hinder water and vapor transport arising from biological tissues, causing potential issues for wearable applications. [12][13][14][15] In addition, poor conformability of dense films on non-developable 3D surfaces is another limitation. [16,17] Kirigami-inspired structures have recently emerged as promising candidates for stretchable electronics. [18][19][20][21][22][23]

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“…52 This leads to difficulties in maintaining a uniaxial stress state, extracting full-field surface deformation, and stretch ratio accurately. To overcome these complications, the geometry and lateral dimensions of the specimen were chosen appropriately, 53 as shown in Figure 2A. Polymers undergo large deformation above the glass transition temperature, T g , even at low loading rates.…”

Section: Mechanical Testingmentioning

confidence: 99%

Strain and temperature induced phase changes inspin‐coated PVDFthin films

Kartheek

Neergat

Jonnalagadda

2023

Journal of Polymer Science

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Poly (vinylidene fluoride) (PVDF) is widely utilized for its unique pyro and piezoelectric properties related to its electro-active β-PVDF. In the past few decades, methods of producing β-PVDF by mechanical stretching of non-polar α-PVDF have been extensively documented. The aim of the present study is to understand the correlation between phase and mechanical behavior of β-PVDF obtained directly from spin-coating, and its stretch-induced transformation from α-PVDF. The effect of thermal annealing and in-plane anisotropy on mechanical properties of spin-coated PVDF freestanding thin films is investigated, under in-situ tensile loading, in conjunction with digital image correlation, to measure the full-field deformation. Stress-strain behavior of spin-coated β-PVDF and α-PVDF are correlated with mechanical stretchinduced phase transformation in α-PVDF. The mechanical strength and failure strain exhibited by spin-coated and annealed α-PVDF

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Fracture in Microscale SU-8 Polymer Thin Films

Cited by 10 publications

References 57 publications

Fabrication and Deformation of 3D Multilayered Kirigami Microstructures

Fabrication and Deformation of 3D Multilayered Kirigami Microstructures

Robust and Multifunctional Kirigami Electronics with a Tough and Permeable Aramid Nanofiber Framework

Strain and temperature induced phase changes inspin‐coated PVDFthin films

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