Transformable 3D electrode system for covering biological tissues

• Applicant: Professor Yoon Seok Park, Ph.D.
• Subject Area: Microsystems ; Biomaterials ; Synthesis and Properties of Functional Materials
• Term: from 2017 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 388060870

Nature is not flat. All objects around us, from huge mountain to micro-scale hair, are curvilinear and have unusual formats. For the purposes of monitoring, treatment, and replacement of biological system in a body, interconnection between living beings and electronics is required. However, since the flat, rigid interfaces of electronic devices are far different from those found in nature, the connection part of conventional electronics is still unsuitable to make proper connections with biological tissues. Thereby, large gaps arise between some parts of the curvilinear tissue and the flat electrode creating only a poor connection for monitoring and stimulating organs. In order to solve these problems, flexible materials that can transform into various shapes are required. In this respect, an ultra-thin flexible contact between the brain and bio-integrated electronics has been studied by the Rogers research group where I am planning to do my post-doc. However, if the size of a wrinkle is shorter than in the brain (< 2 mm), as in the retina of eyes (0.5 – 4 µm), the flexibility of the electrode alone is not enough and the coverage of the device on the cells will be insufficient. For this purpose, we propose a transformable 3D electrode system. The transformable electrode system is a combination of an existing technique, the assembly of 3D structures by compressive buckling, and a new way to keep stretched silicone substrates under tensile stress. The compressive buckling is uses by two components: The first is a stretched silicone substrate and the other is a 2D structure attached to the stretched substrate. The 2D structure will compress and transform to 3D, when the tensile stress on the substrate is released. In order to maintain the tensile stress on the stretched silicone a second technique is required: a water-dissoluble silk fibroin will be coated on the stretched silicone substrate and dissolved when compressive buckling of the electrode is required. The working principle of the transformable electrode system is (i) first the 2D structure that will be transformed to 3D electrode is prepared on the strain-maintaining layer by transfer printing and (ii) the prepared transformable electrode is positioned on the targeted tissue. (iii) After attaching to the tissue, the water-dissolvable layer will be degraded and the tensile stress of the stretched silicone substrate will be released. (iv) Finally, the 2D electrode transforms into a 3D structure, providing intimate contact to the curvilinear tissue. The proposed idea can provide a high performance interconnection between electronics and complex biological tissues (e.g. brain, spinal cord and retina), and thereby enabling highly accurate monitoring or stimulation by these contacts.

• DFG Programme: Research Fellowships
• International Connection: USA
• Participating Institution: Northwestern University ; Department of Materials Science and Engineering
• Host: Professor John A. Rogers, Ph.D.