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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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/.
Custom code used in this study is available at https://osf.io/abyq2/.
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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).
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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Supplementary Figs. 1–34, descriptions of Supplementary Videos 1–4, Methods and References.
Laser pacing of an isolated heart.
Heart pacing and control conditions.
Optical stimulation of a sciatic nerve.
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
Nature Materials (2022)