Biomedical Microdevices

, Volume 15, Issue 6, pp 925–939 | Cite as

A comparison of polymer substrates for photolithographic processing of flexible bioelectronics

  • Dustin Simon
  • Taylor Ware
  • Ryan Marcotte
  • Benjamin R. Lund
  • Dennis W. SmithJr.
  • Matthew Di Prima
  • Robert L. Rennaker
  • Walter VoitEmail author


Flexible bioelectronics encompass a new generation of sensing devices, in which controlled interactions with tissue enhance understanding of biological processes in vivo. However, the fabrication of such thin film electronics with photolithographic processes remains a challenge for many biocompatible polymers. Recently, two shape memory polymer (SMP) systems, based on acrylate and thiol-ene/acrylate networks, were designed as substrates for softening neural interfaces with glass transitions above body temperature (37 °C) such that the materials are stiff for insertion into soft tissue and soften through low moisture absorption in physiological conditions. These two substrates, acrylate and thiol-ene/acrylate SMPs, are compared to polyethylene naphthalate, polycarbonate, polyimide, and polydimethylsiloxane, which have been widely used in flexible electronics research and industry. These six substrates are compared via dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), and swelling studies. The integrity of gold and chromium/gold thin films on SMP substrates are evaluated with optical profilometry and electrical measurements as a function of processing temperature above, below and through the glass transition temperature. The effects of crosslink density, adhesion and cure stress are shown to play a critical role in the stability of these thin film materials, and a guide for the future design of responsive polymeric materials suitable for neural interfaces is proposed. Finally, neural interfaces fabricated on thiol-ene/acrylate substrates demonstrate long-term fidelity through both in vitro impedance spectroscopy and the recording of driven local field potentials for 8 weeks in the auditory cortex of laboratory rats.


Flexible electronics Smart polymers Neural interfaces 



The authors would like to thank the FDA for the use of the Bruker Contour GT-K1 3D Optical Microscope. The opinions and/or conclusions expressed are solely those of the authors and in no way imply a policy or position of the Food and Drug Administration. This material is based partially based upon work supported from several sources: the National Institutes of Neurological Disorders and Stroke 5R01DC008982; the National Science Foundation Partnerships for Innovation and Graduate Research Fellowship under Grant No. 1147385; FUSION support from the State of Texas.

Author declaration

“Syzygy Memory Plastics, Inc. funds undergraduate research in the Advanced Polymers Research Laboratory (APRL) at the University of Texas at Dallas. Taylor Ware and Walter Voit have a significant financial interest in Syzygy Memory Plastics, Inc. This financial interest has been disclosed to UT Dallas and a conflict of interest management plan is in place to manage the potential conflict of interest associated with this research program.”

Supplementary material

10544_2013_9782_MOESM1_ESM.docx (1.4 mb)
ESM 1 (DOCX 1383 kb)


  1. A. Altuna, L. Menendez de la Prida, E. Bellistri, G. Gabriel, A. Guimerá, J. Berganzo, R. Villa, L.J. Fernández, SU-8 based microprobes with integrated planar electrodes for enhanced neural depth recording. Biosens. Bioelectron. 37(1), 1–5 (2012)CrossRefGoogle Scholar
  2. M. Behl, A. Lendlein, Shape-memory polymers. Materials Today 10(4), 20–28 (2007)CrossRefGoogle Scholar
  3. M. Berggren, A. Richter–Dahlfors, Organic bioelectronics. Adv. Mater. 19(20), 3201–3213 (2007)CrossRefGoogle Scholar
  4. M. Cakmak, Y.D. Wang, M. Simhambhatla, Processing characteristics, structure development, and properties of uni and biaxially stretched poly(ethylene 2,6 naphthalate) (PEN) films. Polym. Eng. Sci. 30(12), 721–733 (1990)CrossRefGoogle Scholar
  5. K.C. Cheung, in Thin-Film Microelectrode Arrays for Biomedical Applications Implantable Neural Prostheses, 2, ed. by D. Zhou, E. Greenbaum (Springer, New York, 2010), pp. 157–190Google Scholar
  6. S.F. Cogan, Neural stimulation and recording electrodes. Annu. Rev. Biomed. Eng. 10(1), 275–309 (2008)CrossRefGoogle Scholar
  7. E. Delivopoulos, I.R. Minev, S.P. Lacour. Evaluation of negative photo-patternable PDMS for the encapsulation of neural electrodes. Neural Engineering (NER), 2011 5th International IEEE/EMBS Conference on, 2011, pp. 490–494.Google Scholar
  8. A.P. Dorey, J. Knight, The variation of resistance of gold films with time and annealing procedure. Thin Solid Films 4(6), 445–451 (1969)CrossRefGoogle Scholar
  9. K. Gall, C.M. Yakacki, Y. Liu, R. Shandas, N. Willett, K.S. Anseth, Thermomechanics of the shape memory effect in polymers for biomedical applications. J. Biomed. Mater. Res. A 73A(3), 339–348 (2005)CrossRefGoogle Scholar
  10. H. Gleskova, I. Cheng, S. Wagner, Z. Suo. Thermomechanical criteria for overlay alignment in flexible thin-film electronic circuits. Appl. Phys Lett. 88(1), 011905-011905-011903 (2006).Google Scholar
  11. O. Graudejus, P. Görrn, S. Wagner, Controlling the morphology of gold films on poly(dimethylsiloxane). ACS Appl. Mater. Interfaces 2(7), 1927–1933 (2010)CrossRefGoogle Scholar
  12. A.R. Grayson, R.S. Shawgo, A.M. Johnson, N.T. Flynn, Y. Li, M.J. Cima, R. Langer, A BioMEMS review: MEMS technology for physiologically integrated devices. Proc. IEEE 92(1), 6–21 (2004)CrossRefGoogle Scholar
  13. W.M. Grill, S.E. Norman, R.V. Bellamkonda, Implanted neural interfaces: biochallenges and engineered solutions. Annu. Rev. Biomed. Eng. 11, 1–24 (2009)CrossRefGoogle Scholar
  14. J.L. Halary, F. Lauprêtre, L. Monnerie. Polymer materials: Macroscopic properties and molecular interpretations (Wiley, Hoboken, NJ, 2011)Google Scholar
  15. J.P. Harris, J.R. Capadona, R.H. Miller, B.C. Healy, K. Shanmuganathan, S.J. Rowan, C. Weder, D.J. Tyler, Mechanically adaptive intracortical implants improve the proximity of neuronal cell bodies. J. Neural Eng. 8(6), 066011 (2011a)CrossRefGoogle Scholar
  16. J.P. Harris, A.E. Hess, S.J. Rowan, C. Weder, C.A. Zorman, D.J. Tyler, J.R. Capadona, In vivo deployment of mechanically adaptive nanocomposites for intracortical microelectrodes. J. Neural Eng. 8(4), 046010 (2011b)CrossRefGoogle Scholar
  17. N.G. Hatsopoulos, J.P. Donoghue, The science of neural interface systems. Annu. Rev. Neurosci. 32, 249 (2009)CrossRefGoogle Scholar
  18. C.E. Hoyle, A.B. Lowe, C.N. Bowman, Thiol-click chemistry: a multifaceted toolbox for small molecule and polymer synthesis. Chem. Soc. Rev. 39(4), 1355–1387 (2010)CrossRefGoogle Scholar
  19. S. Isoda, M. Kochi, H. Kambe, Molecular aggregation of solid aromatic polymers. II. Mechanical properties of aromatic polyimide film. J. Polym. Sci. Polym. Phys. Ed. 20(5), 837–844 (1982)CrossRefGoogle Scholar
  20. P. Jin, N. Liu, J. Lin, J. Tan, P.D. Prewett, Replication of micro-optical elements with continuous relief by ultraviolet embossing with thiol-ene-based resist. Appl. Opt. 50(21), 4063–4067 (2011)CrossRefGoogle Scholar
  21. D.R. Kipke, W. Shain, G. Buzsáki, E. Fetz, J.M. Henderson, J.F. Hetke, G. Schalk, Advanced neurotechnologies for chronic neural interfaces: new horizons and clinical opportunities. J. Neurosci. 28(46), 11830 (2008)CrossRefGoogle Scholar
  22. T.Y. Lee, J. Carioscia, Z. Smith, C.N. Bowman, Thiol−Allyl Ether−Methacrylate ternary systems. Evolution mechanism of polymerization-induced shrinkage stress and mechanical properties. Macromolecules 40(5), 1473–1479 (2007)CrossRefGoogle Scholar
  23. A. Lendlein, S. Kelch, Shape-memory polymers. Angew. Chem. Int. Ed. 41, 2034 (2002)CrossRefGoogle Scholar
  24. A. Lendlein, R. Langer, Biodegradable, elastic shape-memory polymers for potential biomedical applications. Science 296(5573), 1673–1676 (2002)CrossRefGoogle Scholar
  25. C. Li, J. Han, C.H. Ahn, Flexible biosensors on spirally rolled micro tube for cardiovascular in vivo monitoring. Biosens. Bioelectron. 22(9–10), 1988–1993 (2007)CrossRefGoogle Scholar
  26. T. Liang, Y. Makita, S. Kimura, Effect of film thickness on the electrical properties of polyimide thin films. Polymer 42(11), 4867–4872 (2001)CrossRefGoogle Scholar
  27. H. Lu, J.A. Carioscia, J.W. Stansbury, C.N. Bowman, Investigations of step-growth thiol-ene polymerizations for novel dental restoratives. Dent. Mater. 21(12), 1129–1136 (2005)CrossRefGoogle Scholar
  28. W.A. MacDonald, M.K. Looney, D. MacKerron, R. Eveson, R. Adam, K. Hashimoto, K. Rakos, Latest advances in substrates for flexible electronics. J. Soc. Inf. Disp. 15(12), 1075–1083 (2007)CrossRefGoogle Scholar
  29. I. Maesoon, C. Il-Joo, W. Fan, K.D. Wise, Y. Euisik. Neural probes integrated with optical mixer/splitter waveguides and multiple stimulation sites. Micro Electro Mechanical Systems (MEMS), 2011 I.E. 24th International Conference on, pp. 1051–1054 (2011).Google Scholar
  30. A. Mata, A. Fleischman, S. Roy, Characterization of polydimethylsiloxane (PDMS) properties for biomedical micro/nanosystems. Biomed. Microdevices 7(4), 281–293 (2005)CrossRefGoogle Scholar
  31. M.A. Meitl, Z.-T. Zhu, V. Kumar, K.J. Lee, X. Feng, Y.Y. Huang, I. Adesida, R.G. Nuzzo, J.A. Rogers, Transfer printing by kinetic control of adhesion to an elastomeric stamp. Nat. Mater. 5(1), 33–38 (2006)CrossRefGoogle Scholar
  32. J.P. Mercier, J.J. Aklonis, M. Litt, A.V. Tobolsky, Viscoelastic behavior of the polycarbonate of bisphenol A. J. Appl. Polym. Sci. 9(2), 447–459 (1965)CrossRefGoogle Scholar
  33. H. Metz, J. McElhaney, A.K. Ommaya, A comparison of the elasticity of live, dead, and fixed brain tissue. J. Biomech. 3(4), 453–458 (1970)CrossRefGoogle Scholar
  34. R.G. Nuzzo, F.A. Fusco, D.L. Allara, Spontaneously organized molecular assemblies. 3. Preparation and properties of solution adsorbed monolayers of organic disulfides on gold surfaces. J. Am. Chem. Soc. 109(8), 2358–2368 (1987)CrossRefGoogle Scholar
  35. G. Pearson, W. Read Jr., W.L. Feldmann, Deformation and fracture of small silicon crystals. Acta Metall. 5(4), 181–191 (1957)CrossRefGoogle Scholar
  36. M.T. Pottiger, J.C. Coburn, J.R. Edman, The effect of orientation on thermal expansion behavior in polyimide films. J. Polymer Sci., Part B: Polymer Phys. 32(5), 825–837 (1994)CrossRefGoogle Scholar
  37. D.T. Reilly, A.H. Burstein, V.H. Frankel, The elastic modulus for bone. J. Biomech. 7(3), 271–275 (1974)CrossRefGoogle Scholar
  38. R.L. Rennaker, S. Street, A.M. Ruyle, A.M. Sloan, A comparison of chronic multi-channel cortical implantation techniques: manual versus mechanical insertion. J. Neurosci. Methods 142(2), 169–176 (2005)CrossRefGoogle Scholar
  39. D.C. Rodger, A.J. Fong, W. Li, H. Ameri, A.K. Ahuja, C. Gutierrez, I. Lavrov, H. Zhong, P.R. Menon, E. Meng, J.W. Burdick, R.R. Roy, V.R. Edgerton, J.D. Weiland, M.S. Humayun, Y.-C. Tai, Flexible parylene-based multielectrode array technology for high-density neural stimulation and recording. Sensors Actuators B Chem. 132(2), 449–460 (2008)CrossRefGoogle Scholar
  40. J.A. Rogers, R.G. Nuzzo, Recent progress in soft lithography. Mater. Today 8(2), 50–56 (2005)CrossRefGoogle Scholar
  41. D.L. Safranski, K. Gall, Effect of chemical structure and crosslinking density on the thermo-mechanical properties and toughness of (meth)acrylate shape memory polymer networks. Polymer 49(20), 4446–4455 (2008)CrossRefGoogle Scholar
  42. T. Saxena, L. Karumbaiah, E.A. Gaupp, R. Patkar, K. Patil, M. Betancur, G.B. Stanley, R.V. Bellamkonda, The impact of chronic blood–brain barrier breach on intracortical electrode function. Biomaterials 34(20), 4703–4713 (2013)CrossRefGoogle Scholar
  43. A.F. Senyurt, H. Wei, C.E. Hoyle, S.G. Piland, T.E. Gould, Ternary Thiol−Ene/Acrylate photopolymers: effect of acrylate structure on mechanical properties. Macromolecules 40(14), 4901–4909 (2007)CrossRefGoogle Scholar
  44. T. Someya, T. Sekitani, S. Iba, Y. Kato, H. Kawaguchi, T. Sakurai, A large-area, flexible pressure sensor matrix with organic field-effect transistors for artificial skin applications. Proc. Natl. Acad. Sci. U. S. A. 101(27), 9966 (2004)CrossRefGoogle Scholar
  45. T. Stieglitz, M. Schuettler, B. Rubehn, T. Boretius, J. Badia, X. Navarro. Evaluation of polyimide as substrate material for electrodes to interface the peripheral nervous system. Neural Engineering (NER), 2011 5th International IEEE/EMBS Conference on, pp. 529–533 (2011).Google Scholar
  46. J. Subbaroyan, D.C. Martin, D.R. Kipke, A finite-element model of the mechanical effects of implantable microelectrodes in the cerebral cortex. J. Neural Eng. 2, 103 (2005)CrossRefGoogle Scholar
  47. A. Ulman, Formation and structure of self-assembled monolayers. Chem. Rev. 96(4), 1533 (1996)CrossRefGoogle Scholar
  48. G. Urban, G. Jobst, F. Keplinger, E. Aschauer, O. Tilado, R. Fasching, F. Kohl, Miniaturized multi-enzyme biosensors integrated with pH sensors on flexible polymer carriers for in vivo applications. Biosens. Bioelectron. 7(10), 733–739 (1992)CrossRefGoogle Scholar
  49. J. Viventi, D.-H. Kim, L. Vigeland, E.S. Frechette, J.A. Blanco, Y.-S. Kim, A.E. Avrin, V.R. Tiruvadi, S.-W. Hwang, A.C. Vanleer, D.F. Wulsin, K. Davis, C.E. Gelber, L. Palmer, J. Van der Spiegel, J. Wu, J. Xiao, Y. Huang, D. Contreras, J.A. Rogers, B. Litt, Flexible, foldable, actively multiplexed, high-density electrode array for mapping brain activity in vivo. Nat. Neurosci. 14(12), 1599–1605 (2011)CrossRefGoogle Scholar
  50. T. Ware, D. Simon, D.E. Arreaga-Salas, J. Reeder, R. Rennaker, E.W. Keefer, W. Voit, Fabrication of responsive, softening neural interfaces. Adv. Funct. Mater. 22(16), 3470–3479 (2012a)CrossRefGoogle Scholar
  51. T. Ware, D. Simon, K. Hearon, C. Liu, S. Shah, J. Reeder, N. Khodaparast, M.P. Kilgard, D.J. Maitland, R.L. Rennaker II, W.E. Voit, Three-dimensional flexible electronics enabled by shape memory polymer substrates for responsive neural interfaces. Macromol. Mater. Eng. 297(12), 1193–1202 (2012b)CrossRefGoogle Scholar
  52. T. Ware, D. Simon, C. Liu, T. Musa, S. Vasudevan, A.M. Sloan, E.W. Keefer, R.L. Rennaker, W. Voit, Thiol-ene/Acrylate substrates for softening intracortical electrodes. J. Biomed. Mater. Res. B Appl. Biomater. (2013). doi: 10.1002/jbmb.32946 Google Scholar
  53. M.L. White, Encapsulation of integrated circuits. Proc. IEEE 57(9), 1610–1615 (1969)CrossRefGoogle Scholar
  54. D.F. Williams, On the mechanisms of biocompatibility. Biomaterials 29(20), 2941–2953 (2008)CrossRefGoogle Scholar
  55. I. Willner, B. Willner, Biomaterials integrated with electronic elements: en route to bioelectronics. Trends Biotechnol. 19(6), 222–230 (2001)CrossRefGoogle Scholar
  56. O. Yizhar, L.E. Fenno, T.J. Davidson, M. Mogri, K. Deisseroth, Optogenetics in neural systems. Neuron 71(1), 9–34 (2011)CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media New York 2013

Authors and Affiliations

  • Dustin Simon
    • 1
  • Taylor Ware
    • 1
  • Ryan Marcotte
    • 3
  • Benjamin R. Lund
    • 4
  • Dennis W. SmithJr.
    • 4
  • Matthew Di Prima
    • 1
    • 6
  • Robert L. Rennaker
    • 5
  • Walter Voit
    • 1
    • 2
    Email author
  1. 1.Department of Materials Science and EngineeringThe University of Texas at DallasRichardsonUSA
  2. 2.Department of Mechanical EngineeringThe University of Texas at DallasRichardsonUSA
  3. 3.Department of Electrical Engineering, MS: EC 33The University of Texas at DallasRichardsonUSA
  4. 4.Department of ChemistryThe University of Texas at DallasRichardsonUSA
  5. 5.School of Brain and Behavioral Sciences, GR 41The University of Texas at DallasRichardsonUSA
  6. 6.Food and Drug Administration, CDRH/OSEL/DSFMSilver SpringUSA

Personalised recommendations