PSI - Issue 37

Shirsha Bose et al. / Procedia Structural Integrity 37 (2022) 131–138 Bose et al., 2021/ Structural Integrity Procedia 00 (2019) 000 – 000

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5c). It is interesting to note that the stress transferred from the collagen to metallic layers were much higher in dry environment (ur Rehman et al., 2012; Xue et al., 2020). The high levels of stress transfer might affect the longevity of these devices. The lower stress level generated in the wet substrate might be beneficial during in-vivo applications. However, these need further investigations especially of the interfacial behaviour. 4. Conclusions and future outlooks The use of collagen film as a substrate in flexible electronics is a contemporary concept, and its successful implementation is subjected to investigations of several factors, one of these being the interfacial adhesion of the softer matrix to stiffer metallic layers. The following are the major conclusions from this study: • The stress generated for the chromium layer in the square micro-island slightly exceeded its yield strength, which is an indication of the onset of plastic deformation. This might affect the performance of this devices. • The collagen-chromium interface exhibited good adhesion at lower strain levels (1.25%). However, with increasing strain, the interfacial delamination grew rapidly for the square micro-island, surpassing that for the circular one. This finding implies that it would be advisable to opt for circular configuration, which would also reduce the cost/weight of the metallic layers. • The wet collagen substrate demonstrated stress levels, which were lower by two orders of magnitude as compared to those for the dry one. Moreover, the stress transferred to the metallic layers in wet conditions was significantly lower. Hence, such devices might be used for in-vivo applications, though further investigations should be done to understand their structural stability. Acknowledgement VVS gratefully acknowledges financial support from the Government of the Russian Federation under the mega grant program, contract no. 075-15-2021-578, 31 May 2021, hosted by Perm National Research Polytechnic Bose, S., Li, S., Mele, E. and Silberschmidt, V. V (2020) ‘Dry vs. wet: Properties and performance of collagen films. Part I. mechanical behaviour and strain- rate effect’, Journal of the Mechanical Behavior of Biomedical Materials, 111, p. 103983. doi: 10.1016/j.jmbbm.2020.103983. Cordill, M. J., Fischer, F. D., Rammerstorfer, F. G. and Dehm, G. (2010) ‘Adhesion energies of Cr thin films on polyimide determined from buckling: Experiment and model’, Acta Materialia, 58(16), pp. 5520– 5531. Espinosa, H. D. and Prorok, B. C. (2003) ‘Size effects on the mechanical behavior of gold thin films’, Journal of Materials S cience, 38(20), pp. 4125 – 4128. Graz, I. M., Cotton, D. P., Robinson, A. and Lacour, S. P. (2011) ‘Silicone substrate with in situ strain relief for stretcha ble thin- film transistors’, Applied Physics Letters, 98(12), p. 124101. Kang, S., Yoon, T., Ma, B. S., Cho, M. S. and Kim, T. S. (2021) ‘Liquid -assisted adhesion control of graphene – copper interface for damage-free mechanical transfer’, Applied Surface Science, 551, p. 149229. Lei, J., Zou, B., Zhang, R., Zhang, K., Xie, R., Zhang, W., Wu, J., Li, S., Zheng, B. and Huo, F. (2019) ‘Regenerating leather waste for flexible pressure sensing applications’, Journal of Leather Science and Engineering, 1(1), pp. 1– 9. Li, H., Wang, Z., Lu, S., Ma, Y. and Feng, X. (2019) ‘Elastomers with microislands as strain isolating substrates for stretchable electronics’, Advanced Materials Technologies, 4(2), p. 1800365. Liao, X., Zhang, Z., Liang, Q., Liao, Q. and Zhang, Y. (2017) ‘Flexible, cuttable, and self -waterproof bending strain sensors using microcracked gold nanofilms@ paper substrat e’, ACS Applied Materials & Interfaces, 9(4), pp. 4151 – 4158. Lin, G., Sun, W. and Chen, P. (2020) ‘Topography - driven delamination of thin patch adhered to wrinkling surface’, International Journal of Mechanical Sciences, 178, p. 105622. Lin, M. T., Tong, C. J. and Shiu, K. S. (2008) ‘Monotonic and fatigue testing of freestanding submicron thin beams application for MEMS’, Microsystem Technologies, 14(7), pp. 1041 – 1048. Lucchini, R., Cattarinuzzi, E., Maraghechi, S., Gastaldi, D., Adami, A., Lorenzelli, L. and Vena, P. (2016) ‘Delamination phenomena in aluminum/polyimide deformable interconnects: In-situ micro- tensile testing’, Materials & Design, 89, pp. 121– 128. University. References Bose, S., Li, S., Mele, E. and Silberschmidt, V. V. (2020) ‘Dry vs. wet: Properties and performance of collagen films. Part I I. Cyclic and time dependent behaviours’, Journal of Mechanical Behaviour of Biomedical Materials, p. 104040. doi: 10.1016/j.jmbbm.2020.104040.