Transient Light‐Emitting Diodes Constructed from Semiconductors and Transparent Conductors that Biodegrade Under Physiological Conditions

Abstract

Transient forms of electronics, systems that disintegrate, dissolve, resorb, or sublime in a controlled manner after a well‐defined operating lifetime, are of interest for applications in hardware secure technologies, temporary biomedical implants, “green” consumer devices and other areas that cannot be addressed with conventional approaches. Broad sets of materials now exist for a range of transient electronic components, including transistors, diodes, antennas, sensors, and even batteries. This work reports the first examples of transient light‐emitting diodes (LEDs) that can completely dissolve in aqueous solutions to biologically and environmentally benign end products. Thin films of highly textured ZnO and polycrystalline Mo serve as semiconductors for light generation and conductors for transparent electrodes, respectively. The emitted light spans a range of visible wavelengths, where nanomembranes of monocrystalline silicon can serve as transient filters to yield red, green, and blue LEDs. Detailed characterization of the material chemistries and morphologies of the constituent layers, assessments of their performance properties, and studies of their dissolution processes define the underlying aspects. These results establish an electroluminescent light source technology for unique classes of optoelectronic systems that vanish into benign forms when exposed to aqueous conditions in the environment or in living organisms.

Bioresorbable Materials on the Rise: From Electronic Components and Physical Sensors to In Vivo Monitoring Systems

“…Dissolution of ZnO in physiological conditions was recently investigated by Lu et al, who used ZnO as semiconductor in the fabrication of bioresorbable light‐emitting diodes (LEDs). ZnO samples (200 µm × 200 µm squares, thickness ≈200 nm) immersed in PBS at pH = 7.4 and 37 °C completely dissolved in 48 h, with a dissolution rate of about 4.1 nm h −1 (≈100 nm day −1 ).…”

“…Copyright 2019, The Authors, Published by American Association for the Advancement of Science. c) Left: Sketch and optical microscope images of the bioresorbable ZnO LED . Middle: Optical microscope images during dissolution of the bioresorbable LED in PBS at pH 7.4 and 37 °C.…”

“…Right: Electrical characteristic of the ZnO LED; insets: optical microscope images showing device electroluminescence. Reproduced with permission . Copyright 2019, John Wiley and Sons.…”

“…Very recently, Lu et al demonstrated a fully bioresorbable LED based on a II–VI semiconductor, namely, ZnO, and an ultrathin transparent electrode of Mo (Figure c), advancing the state‐of‐the‐art research on this subject, with respect to partially biodegradable riboflavin‐ and peptide‐based organic LEDs, and demonstrating full biodegradability of the two key elements of a LED, namely, direct bandgap semiconductor that allows recombination of injected electrons and holes for light emission, and transparent electrode that allows escaping of the emitted light. Specifically, a ZnO layer (200 nm thick) used as n‐type semiconductor was deposited on top of a Si (12 µm thick) membrane used as p‐type semiconductor, whereas W (100 nm) and Mo (8 nm) were used for electrical contacts.…”

Materials, Mechanics Designs, and Bioresorbable Multisensor Platforms for Pressure Monitoring in the Intracranial Space

“…Here, bioresorbable constituent materials minimize inflammatory responses and eliminate the need for secondary surgical extraction. [ 9–13 ] Recent examples include not only pressure but also temperature sensors for the intracranial space; [ 14–16 ] photonic devices for monitoring physiological status and neural activity; [ 17 ] wireless electronic systems for neuroregenerative therapy; [ 18 ] platforms for spatiotemporal mapping of electrical activity from the cerebral cortex; [ 19 ] drug release vehicles for infection abatement; [ 20 ] and systems for measuring blood flow. [ 21 ] Realizing consistent performance throughout a clinically relevant monitoring period with devices that bioresorb completely over slightly longer timescales represents an important goal.…”