3D‐Printed Autonomous Sensory Composites

Abstract

materials (solids, thin-films, and liquids) and functions into a single seamless autonomous sensory composite by avoiding the use of a premade substrate, and 3D-printing all required materials without any external processing.We present a monolithic integration of strain sensitive elements with an organic electrochemical transistor (OECT)based amplifier and an electrochromic element powered at 1.5 V DC fabricated using a low-temperature additive manufacturing approach (additive manufacturing system is shown in Figure 1B; integration scheme of the composite is in Figure 1C and photograph is shown in Figure 1D). There are two challenges in material interface engineering that currently limit the creation of functional 3D composites using a single fabrication method. First, local control of surface energy and texture at material interfaces is essential to assemble multiple materials, specifically for confining solvent inks on solid layers with high fidelity. [22] Similarly, controlling the droplet deployment order is essential (see the Experimental Section and Figure S1, Supporting Information). Second, reducing the operating voltage in active electrical signal processors is strongly tied to achieving defect-free, extremely uniform, thin gate dielectrics in field effect transistors or encapsulating electrolytes in OECTs. We solve this by using a drop-on-demand multimaterial inkjetbased 3D printing platform (see Figure 1B) that is capable of printing UV curable materials with a ≈35 µm lateral resolution [23] while simultaneously printing solvent-evaporated films, and encapsulated liquids (images of droplets in-flight and printed lines are in Figure S2, Supporting Information). Equipped with light-emitting diode (LED) arrays for UV curing, the system can digitally assemble UV curable polymers of varying elastic moduli and surface energies. Droplets of different materials are deployed simultaneously to assemble multiple materials in the same layer, where the resolution is the size of each droplet. When solvent-based inks are printed, a compact ceramic heater on the printhead carriage enables rapid local forced convection heating of the uppermost printed layers. Printed liquids can be confined by sidewalls and also be completely encapsulated inside UV curable matrices. The structure of the final composite to be printed is represented as voxels (volume elements), where the choice of the material for each voxel is made based on the required function. In total, six different materials are printed here (ink compositions are in Table S1, Supporting Information); full details of the materials and the printing process are in the Experimental Section and the Supporting Information.The mechanical matrix of the autonomous sensory composite is made from a basis of two UV curable acrylate polymer materials of varying mechanical stiffness; rigid formulation (elastic modulus ≈637.76 MPa) and the elastic material (elastic modulus ≈678.5 kPa) span three orders of magnitude in stiffness ( Figure S3, Supporting Information). The active reg...

Recent Progress in Biomimetic Additive Manufacturing Technology: From Materials to Functional Structures

“…The selection of these composites is ultimately depends on the design requirements of electronic devices and the type of 3D‐printing processes to be used. The fillers are a key in 3D‐printing materials, which could be organic, metallic, ceramic, or combinations of thereof . The binder helps the homogeneous dispersion of fillers as well as binding the fillers together.…”

“…The inkjet printing process relies on localized and controlled ink dispensing onto the substrate, which can fabricate electronic sensor with a wide variety of materials including metal, organic, ceramic, and colloid. However, limited by the nozzle size, the resolution of this method is usually larger than 30 μm . The stereolithography‐based 3D printing and the direct laser writing processes are widely used for much smaller resolution that could go down to 200 nm .…”

“…d) Schematic of printing process (left), optical image of autonomous sensory system (middle), and pixel change when the strain sensor is extended (right). Reproduced with permission . Copyright 2017, Wiley‐VCH.…”

3D Printed Polymer Photodetectors

“…3D printing of electronic materials is an emerging fabrication method for devices such as electrodes, batteries, strain sensors, capacitors, antennas, electrically driven soft actuators, and radio frequency transmitters . These devices have been used in a number of applications including the augmentation of cellular constructs and organ models with electrical components such as sensors and antennas, the direct printing of electronic devices on moving surfaces including human hands, and artificial electronic skins .…”

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“…Enabling materials and technology to address this unmet need would pave the way for real freedom‐of‐design of unique devices and sensors due to out‐of‐plane functional electronics . Immediate fields that would benefit from advancement in this field are biomedical devices, antennas, soft robotics, and in general, Internet of things (IoT) applications . One approach to obtaining electronics on 3D surfaces is based on printing electrical circuits on flat surface, followed by reshaping them into 3D structures.…”