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Porosity-based heterojunctions enable leadless optoelectronic modulation of tissues

Abstract

Homo- and heterojunctions play essential roles in semiconductor-based devices such as field-effect transistors, solar cells, photodetectors and light-emitting diodes. Semiconductor junctions have been recently used to optically trigger biological modulation via photovoltaic or photoelectrochemical mechanisms. The creation of heterojunctions typically involves materials with different doping or composition, which leads to high cost, complex fabrications and potential side effects at biointerfaces. Here we show that a porosity-based heterojunction, a largely overlooked system in materials science, can yield an efficient photoelectrochemical response from the semiconductor surface. Using self-limiting stain etching, we create a nanoporous/non-porous, soft–hard heterojunction in p-type silicon within seconds under ambient conditions. Upon surface oxidation, the heterojunction yields a strong photoelectrochemical response in saline. Without any interconnects or metal modifications, the heterojunction enables efficient non-genetic optoelectronic stimulation of isolated rat hearts ex vivo and sciatic nerves in vivo with optical power comparable to optogenetics, and with near-infrared capabilities.

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Fig. 1: Nanoporous/non-porous silicon materials enable efficient photoelectrochemical effects, and their biomimetic structure makes them suitable for application in biointerfaces.
Fig. 2: Microscopy analysis of the material structure.
Fig. 3: Screening of etching conditions for photocurrent generation.
Fig. 4: Electrochemical analysis of the nanoporous silicon.
Fig. 5: Pacing of isolated hearts ex vivo.
Fig. 6: In vivo sciatic nerve stimulation.

Data availability

All data supporting the results of this study are presented in the manuscript or the Supplementary Information. All raw data are available at https://osf.io/abyq2/.

Code availability

Custom code used in this study is available at https://osf.io/abyq2/.

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Acknowledgements

We thank K. Watters for scientific editing of the manuscript. This work was supported by the US Air Force Office of Scientific Research (FA9550-18-1-0503, FA9550-20-1-0387), the National Science Foundation (NSF DMR-2105321, NSF CBET-2128140, NSF MPS-2121044) and the US Army Research Office (W911NF-21-1-0090). A.P. acknowledges support from the Materials Research Science and Engineering Center-funded Graduate Research Fellowship (NSF DMR-2011854). This work made use of the Pritzker Nanofabrication Facility at the Pritzker School of Molecular Engineering at the University of Chicago, which receives support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-2025633), a node of the National Science Foundation’s National Nanotechnology Coordinated Infrastructure; the Scanning Probe Imaging and Development facility of the Northwestern University Atomic and Nanoscale Characterization Experimental Center, which has received support from the SHyNE Resource (NSF ECCS-2025633); the International Institute for Nanotechnology; and Northwestern’s MRSEC programme (NSF DMR-1720139). We acknowledge the MRSEC Shared User Facilities at the University of Chicago (NSF DMR-1420709) and the shared facilities at the University of Chicago Materials Research Science and Engineering Center, supported by the National Science Foundation under award number DMR-2011854. We acknowledge the support of J. Jureller with imaging and materials characterization. A.P. thanks G. Olack for assistance with STEM sample preparation using focused ion beam milling. We thank F. Shi for the help on the STEM imaging; this work made use of instruments in the Electron Microscopy Service (Research Resources Center, University of Illinois Chicago).

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Authors and Affiliations

Authors

Contributions

B.T. supervised the research. A.P. and B.T. conceived the nanoporous/non-porous heterojunction concept. M.Y.R. initiated the project, made the initial observations and performed preliminary experiments. A.P. performed the majority of the experiments and data collection. J.S., P.L., Y.L. and J.P. assisted with the material characterization. J.Y. assisted with the in vivo experiments. A.P. wrote the computer code for data analysis. A.P. and M.Y.R. prepared the manuscript with input from all other authors.

Corresponding authors

Correspondence to Bozhi Tian or Menahem Y. Rotenberg.

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Competing interests

University of Chicago filed provisional patent applications for the synthesis of porous silicon materials and their applications to biomodulation. Inventors: B.T., A.P. and M.Y.R. All remaining authors declare no competing interests.

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Nature Materials thanks Silvestro Micera, Nicolas Voelcker and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary information

Supplementary Information

Supplementary Figs. 1–34, descriptions of Supplementary Videos 1–4, Methods and References.

Reporting Summary.

Supplementary Video 1

Laser pacing of an isolated heart.

Supplementary Video 2

Heart pacing and control conditions.

Supplementary Video 3

Optical stimulation of a sciatic nerve.

Supplementary Video 4

Stimulation of a sciatic nerve through an optical fibre.

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Prominski, A., Shi, J., Li, P. et al. Porosity-based heterojunctions enable leadless optoelectronic modulation of tissues. Nat. Mater. 21, 647–655 (2022). https://doi.org/10.1038/s41563-022-01249-7

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