Despite these vibrant innovations in bioelectronic devices and their ever advanced applications, the integration of bioelectronic devices to the human body still rely on century-old conventional methods such as surgical suturing or just physically place on top of tissues. These old approaches suffer from various limitations and challenges, including non-conformal contact, unstable electrical communications, and/or tissue damage. For example, surgically sutured epicardial pacing wires (used for short-term cardiac pacing after cardiac surgeries) often cause dreaded and life-threatening complications such as arrhythmias and tamponade.

 As a research group working on bioadhesive technologies (check our works on bioadhesives including Nature 575, 169-174, 2019; PNAS 117, 15497-15503, 2020), we were naturally interested on these challenges to seek an opportunity to offer a new promising solution based on our expertise. One day during endless brainstorming discussions, we picked up a 3M conductive tape in the corner of our laboratory that we typically use to adhere electronic elements to a printed circuit board (PCB) without using solders for a quick check. Right after seeing it, all of us asked one question almost simultaneously – Can we make something like this working for biological tissues?

After this Eureka moment, we systematically studied functional requirements that would be needed to provide ideal integration of bioelectronic devices to wet dynamic tissues overcoming the limitations of existing approaches. Based on literature reviews and discussions with various colleagues both in the academic side and clinical side (surgeons who use implantable electronics such as cardiac pacing wires), we boiled down several key requirements we needed to achieve: 1) Rapid and robust adhesion to wet dynamic tissue surface, 2) high electrical conductivity and charge injection capacity to allow electrical communications, 3) minimal to no adverse effect such as geometric distortion of delamination failure to the integrated bioelectronic devices, 4) atraumatic and on-demand retrieval of integrated bioelectronic devices.

Like all research projects, it turned out that achieving all of the functional requirements in one material was a highly non-trivial and challenging task. We could easily achieve the first requirement of rapid robust wet adhesion by taking advantage of our previous works on bioadhesives, but it simply could not satisfy other requirements. The first challenge was the poor electrical conductivity of most of the tissue adhesives including our bioadhesives that were far lower than what would be needed to ensure uninterrupted electrical communication between the bioelectronic devices and underlying tissues. The second challenge was the swelling of most tissue adhesive materials that can cause geometric distortion, delamination failures, and substantially decreased electrical functionality of bioelectronic devices.

After failing countless attempts to solve these seemingly intrinsic dilemmas, a long-sought solution came from a rather obvious source. One day, tired with another failed attempt, Jue suggested a rather silly idea – how about using graphene since I used it a lot during Ph.D.? While we felt it is kind of random thing to try as we did not have a rational guess, we just did it. To our surprise, the resultant dark-colored bioadhesive showed all properties we needed just in 1^st trial. It almost perfectly retained highly favorable rapid and robust wet adhesion capability; it had very high electrical conductivity; and most surprisingly, it only swelled orthogonally to the adhesion interface without lateral swelling (so did not affect the bioadhesive device at all). After a more careful investigation, it turned out that graphene mixed with the bioadhesive networks formed highly percolated and ordered lamellar microstructures that gave favorable mechanical properties without affecting bioadhesive capability, high electrical conductivity and charge injection capacity, and anisotropic swelling behavior. Excited on the lucky finding, we did more careful optimization of this material, and later proudly named it as the electrical bioadhesive interface (or e-bioadhesive interface) for bioelectronic devices.

Taking the unique advantages of the e-bioadhesive interface, we demonstrated several proof-of-concept applications of the e-bioadhesive interface including in vivo epicardial ECG recording and in vivo peripheral nerve stimulation. We hope that this newly available capability can benefit a broad range of bioelectronic devices to upgrade them into bioadhesive electronics and offer new opportunities for novel bioelectronic devices and applications. We envision that our e-bioadhesive can accelerate the translation and ultimate adoption of various bioelectronic devices into real clinical applications. With our new e-bioadhesive technology, we wish it can become a general platform for bioelectronic devices both in academic and industrial sectors and provides valuable insights for the future development of biointegrative electronics.

For more details, check out our paper “Electrical bioadhesive interface for bioelectronics” on Nature Materials. 

Jue Deng & Hyunwoo Yuk

Massachusetts Institute of Technology