title: 3D printed quantum dot light-emitting diodes.
abstract: Developing the ability to 3D print various classes of materials possessing distinct properties could enable the freeform generation of active electronics in unique functional, interwoven architectures. Achieving seamless integration of diverse materials with 3D printing is a significant challenge that requires overcoming discrepancies in material properties in addition to ensuring that all the materials are compatible with the 3D printing process. To date, 3D printing has been limited to specific plastics, passive conductors, and a few biological materials. Here, we show that diverse classes of materials can be 3D printed and fully integrated into device components with active properties. Specifically, we demonstrate the seamless interweaving of five different materials, including (1) emissive semiconducting inorganic nanoparticles, (2) an elastomeric matrix, (3) organic polymers as charge transport layers, (4) solid and liquid metal leads, and (5) a UV-adhesive transparent substrate layer. As a proof of concept for demonstrating the integrated functionality of these materials, we 3D printed quantum dot-based light-emitting diodes (QD-LEDs) that exhibit pure and tunable color emission properties. By further incorporating the 3D scanning of surface topologies, we demonstrate the ability to conformally print devices onto curvilinear surfaces, such as contact lenses. Finally, we show that novel architectures that are not easily accessed using standard microfabrication techniques can be constructed, by 3D printing a 2 × 2 × 2 cube of encapsulated LEDs, in which every component of the cube and electronics are 3D printed. Overall, these results suggest that 3D printing is more versatile than has been demonstrated to date and is capable of integrating many distinct classes of materials.
authors.affiliation: Department of Mechanical and Aerospace Engineering, Princeton University , Princeton, New Jersey 08544, United States.
authors.forename: Yong Lin
authors.initials: YL
authors.lastname: Kong
authors.forename: Ian A
authors.initials: IA
authors.lastname: Tamargo
authors.forename: Hyoungsoo
authors.initials: H
authors.lastname: Kim
authors.forename: Blake N
authors.initials: BN
authors.lastname: Johnson
authors.forename: Maneesh K
authors.initials: MK
authors.lastname: Gupta
authors.forename: Tae-Wook
authors.initials: TW
authors.lastname: Koh
authors.forename: Huai-An
authors.initials: HA
authors.lastname: Chin
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Steingart
authors.forename: Barry P
authors.initials: BP
authors.lastname: Rand
authors.forename: Michael C
authors.initials: MC
authors.lastname: McAlpine
keywords: 3D printing; additive manufacturing; hybrid materials integration; interwoven electronics; quantum dot light-emitting devices