Fully Stretchable Optoelectronic Sensors Based on Colloidal Quantum Dots for Sensing Photoplethysmographic Signals

TLDR

Flexible and stretchable optoelectronic devices, enabled by nanomaterials such as quantum dots, hold promise for displays, biosensors, robotics, and energy generation, but require careful structural design and material selection to achieve stretchability. This study reports stretchable optoelectronic sensors fabricated from colloidal quantum dots on elastomeric substrates whose optoelectronic properties remain stable under various deformations. The sensors employ a graphene electrode for extreme bendability, and ultrathin QD LEDs and photodetectors are transfer‑printed onto a prestrained elastomeric layout that forms wavy, buckled structures capable of stretching to a flat configuration while maintaining emissive and active areas. We demonstrate that these stretchable sensors can continuously monitor blood waves via photoplethysmography, offering a new class of foldable, health‑monitoring optoelectronic devices that meet the demand for wearable electronics.

Abstract

Flexible and stretchable optoelectronic devices can be potentially applied in displays, biosensors, biomedicine, robotics, and energy generation. The use of nanomaterials with superior optical properties such as quantum dots (QDs) is important in the realization of wearable displays and biomedical devices, but specific structural design as well as selection of materials should preferentially accompany this technology to realize stretchable forms of these devices. Here, we report stretchable optoelectronic sensors manufactured using colloidal QDs and integrated with elastomeric substrates, whose optoelectronic properties are stable under various deformations. A graphene electrode is adopted to ensure extreme bendability of the devices. Ultrathin QD light-emitting diodes and QD photodetectors are transfer-printed onto a prestrained elastomeric layout to form wavy configurations with regular patterns. The layout is mechanically stretchable until the structure is converted to a flat configuration. The emissive and active area itself can be stretched or compressed by buckled structures, which are applicable to wearable electronic devices. We demonstrate that these stretchable optoelectronic sensors can be used for continuous monitoring of blood waves via photoplethysmography signal recording. These and related systems create important and unconventional opportunities for stretchable and foldable optoelectronic devices with health-monitoring capability and, thus, meet the demand for wearable and body-integrated electronics.