Active Bioelectronic Systems with Large-Scale Silicon-Nanomembrane Transistor Array as Chronic Neural Interfaces 

Enming Song* 

* Institute of Optoelectronics, Fudan University, Shanghai 200433, China (sem@fudan.edu.cn)

Abstract 

Flexible engineered systems that establish high-performance, long-lived electrical interfaces to the brain and other tissue parts, at a variety of scales ranging from individual-neuron resolution level to macroscopic area coverage, are of particular interest to the neuroscience and biomedical researches [1-4]. Conventional material approaches of state-of-art, fully-integrated electronic systems, such as deep brain stimulators, pacemakers and cochlear implants, generally feature stiff, thick (millimeter-scale) materials constructed by bulk metal, ceramics and wafers [5]. These resulting systems directly contact or insert into adjacent surface of bio-tissues by passive, rigid electrodes, where the materials used for these systems are fundamentally mismatched with the curved, compliant and time-dynamic tissues, with the potential of injury and associated foreign-body response that induces device degradation at biotic/electrode interfaces [6]. Here, our work reports a scalable approach with microscale transfer-printing technology to establish flexible bioelectronic systems that can integrate tens of thousands of single-crystalline silicon nanomembrane (Si-NM) transistors (100 nm thick) in interconnected arrays as functional neural interfaces on thin polymer substrates across full-scale brain dimension [4,7,8]. Specifically, the advanced technology has been exploited for deterministic assembly of prefabricated microelectronic devices sourced from semiconductor wafers, using patterned poly (dimethylsiloxane) (PDMS) stamps [7,9]. This scheme, as shown in Figures 1a and 1b, can support rapid, parallel transfer of large collections of variable types of devices (e.g. > 32,000 CMOS transistors and inorganic light emitted diodes) from rigid, planar silicon wafers to shape-conformal membranes as receiving surfaces, with various densities and pitch spacings across large areas (~150 cm2 ) on polymer films for neural electrophysiological mapping [7,10,11]. The scales of the demonstrated electronic neural interfaces yield significance of importance, with magnitudes of values that greatly surpass those from previous publications [12]. Subsequent cointegration of these bioelectronic systems with thermally grown SiO2 at submicron thickness that serves as biofluid barriers can offer long-term stability, over projected lifetime across many decades of in-vivo implantation in human brain [6,10]. Results will create significant opportunities for flexible bio-integrated electronic systems as chronic neural implants in animal model studies and human healthcare [13]

Fig. 1. Photographs of a large collection of silicon nanomembrane transistors (total ~32,000) printed on a large polymer film cut into the approximate outline of a human brain, while flat (a) and bent (b). Inset shows device yield as function of printing number.

References 

1. E. Song, et al., “Materials for flexible bioelectronic systems as chronic neural interfaces," Nat. Mater., 19 (2020) 590. 2. E. Song, et al., “ Miniaturized electromechanical devices for the characterization of the biomechanics of deep tissue." Nat. Biomed. Eng., 5, (2021) 759. 3. S. M. Won # , E. Song # , J. Reeder # & J. A. Rogers * , “Emerging modalities and implantable technologies for neuromodulation," Cell, 181 (2020) 115. 4. E. Song et al., “Flexible electronic/optoelectronic microsystems with scalable designs for chronic biointegration,” Proc. Natl. Acad. Sci., 116 (2019) 15398. 5. E. Song et al., “Ultrathin trilayer assemblies as long-lived barriers against water and ion penetration in flexible bioelectronic systems,” ACS Nano, 12 (2018) 10317. 6. E. Song, J. Li & J. A. Rogers, “Barrier materials for flexible bioelectronic implants with chronic stability—current approaches and future directions,” APL Mater., 7 (2019) 050902. 7. E. Song et al., “Thickness-dependent electronic transport in ultrathin single crystalline silicon nanomembranes," Adv. Electron. Mater., 5 (2019) 1900232. 8. E. Song et al., “Recent advances in microsystem approaches for mechanical characterization of soft biological tissues,” Microsystems and Nanoengineering, 8 (2022) 77. 9. E. Song et al., “Bendable photodetector on fibers wrapped with flexible ultra-thin single crystalline silicon nanomembranes,” ACS Appl. Mater. Interfaces, 9 (2017) 12171. 10. E. Song et al., “Transferred, ultrathin oxide bilayers as biofluid barriers for flexible electronic implants,” Adv. Funct. Mater., 28 (2018) 1702284. 11. E. Song, et al., “Thin, transferred layers of silicon dioxide and silicon nitride as water and ion barriers for implantable flexible electronic systems," Adv. Electron. Mater., 3 (2017) 1700077. 12. S. M. Won # , E. Song # , J. Zhao, J. Li, J. Rivnay & J.A. Rogers * , "Recent advances in materials, devices, and systems for neural interfaces," Adv. Mater., 30 (2018)1800534. 13. E. Song, et al., “Soft, biocompatible materials and skin-like electronics as wearable devices: an interview with John A. Rogers,” National Science Review, 10 (2023) nwac191.