The integration of 3D printed sensors into hosting structures has become a growing area of research due to simplified assembly procedures, reduced system complexity, and lower fabrication cost. Embedding 3D printed sensors into structures or bonding the sensors on surfaces are the two techniques for the integration of sensors. This review extensively discusses the fabrication of sensors through different additive manufacturing techniques. Various additive manufacturing techniques dedicated to manufacture sensors as well as their integration techniques during the manufacturing process will be discussed. This review will also discuss the basic sensing mechanisms of integrated sensors and their applications. It has been proven that integrating 3D printed sensors into infrastructures can open new possibilities for research and development in additive manufacturing and sensor materials for smart goods and the Internet of Things.

Recently, the manufacturing of porous polydimethylsiloxane (PDMS) with engineered porosity has gained considerable interest due to its tunable material properties and diverse applications. An innovative approach to control the porosity of PDMS is to use transient liquid phase water to improve its mechanical properties, which has been explored in this work. Adjusting the ratios of deionized water to the PDMS precursor during blending and subsequent curing processes allows for controlled porosity, yielding water emulsion foam with tailored properties. The PDMS-to-water weight ratios were engineered ranging from 100:0 to 10:90, with the 65:35 specimen exhibiting the best mechanical properties with a Young’s Modulus of 1.17 MPa, energy absorption of 0.33 MPa, and compressive strength of 3.50 MPa. This led to a porous sample exhibiting a 31.46% increase in the modulus of elasticity over a bulk PDMS sample. Dowsil SE 1700 was then added, improving the storage capabilities of the precursor. The optimal storage temperature was probed, with −60 °C resulting in great pore stability throughout a three-week duration. The possibility of using these water emulsion foams for paste extrusion additive manufacturing (AM) was also analyzed by implementing a rheological modifier, fumed silica. Fumed silica’s impact on viscosity was examined, revealing that 9 wt% of silica demonstrates optimal rheological behaviors for AM, bearing a viscosity of 10,290 Pa·s while demonstrating shear-thinning and thixotropic behavior. This study suggests that water can be used as pore-formers for PDMS in conjunction with AM to produce engineered materials and structures for aerospace, medical, and defense industries as sensors, microfluidic devices, and lightweight structures.

Understanding the mechanical properties of three-dimensional (3D)-printed ceramics while keeping the parts intact is crucial for advancing their application in high-performance and biocompatible fields, such as biomedical and aerospace engineering. This study uses non-destructive nanoindentation techniques to investigate the mechanical performance of 3D-printed zirconia across pre-conditioned and sintered states. Vat photopolymerization-based additive manufacturing (AM) was employed to fabricate zirconia samples. The structural and mechanical properties of the printed zirconia samples were explored, focusing on hardness and elastic modulus variations influenced by printing orientation and post-processing conditions. Nanoindentation data, analyzed using the Oliver and Pharr method, provided insights into the elastic and plastic responses of the material, showing the highest hardness and elastic modulus in the 0° print orientation. The microstructural analysis, conducted via scanning electron microscopy (SEM), illustrated notable changes in grain size and porosity, emphasizing the influencing of the printing orientation and thermal treatment on material properties. This research uniquely investigates zirconia’s mechanical evolution at the nanoscale across different processing stages—pre-conditioned and sintered—using nanoindentation. Unlike prior studies, which have focused on bulk mechanical properties post-sintering, this work elucidates how nano-mechanical behavior develops throughout additive manufacturing, bridging critical knowledge gaps in material performance optimization.

Additive manufacturing (AM) enables the integration of multiple materials into architected designs with tailored functional material performance. In this work, modular layered structures composed of barium titanate (BTO) and polylactic acid (PLA) were fabricated using direct ink writing and fused filament fabrication to investigate compressive properties and directional piezoelectric sensing. Mechanical testing indicated that bulk BTO demonstrated high stiffness but was prone to brittle failure. In contrast, PLA exhibited ductile behavior with lower strength. However, the layered PLA-BTO structure achieved an optimal balance between strength and strain tolerance, facilitated by interlayer sliding and stress redistribution. Cyclic compressive testing conducted under a load of 5 N along the predetermined sensing axis exhibited significant directional piezoelectric selectivity in the layered PLA/BTO structure. This observation underscores the highly anisotropic piezoelectric performance of the structure, with the most pronounced voltage output along the x -axis (approximately 2.2 V), moderate response along the y -axis (approximately 0.9 V), and negligible activity along the z -axis (approximately 0.04 V). This anisotropy sensing capability is attributed to structural segmentation, where PLA layers act as insulating barriers and BTO layers form continuous charge pathways along selected axes. These results highlight the potential of AM-enabled layered architectures for programmable anisotropy, offering pathways toward localized directional sensing and energy-harvesting applications in robotics, aerospace, and structural health monitoring.

: Additive manufacturing enables the design of architected piezoelectric materials with tunable geometry and capacitive enhancement. In this work, field’s metal (FM) (32.5% Bi, 51% In, 16.5% Sn) infiltration was introduced as a novel strategy to enhance overall dielectric capacitance and charge transport within 3D-printed barium titanate (BTO) lattices. A 40 vol% BTO photopolymer resin (BT40) was formulated for digital light processing to fabricate 3D gyroid architectures with different controlled porosities. Following debinding and sintering to 96% theoretical density, and thermal poling ( d ₃₃ ≈ 120 pC N ⁻¹ ), the lattices were infiltrated with molten FM below the BTO Curie temperature (∼125 °C), forming continuous metallic networks. Rheological and optical analyses confirmed shear-thinning behavior and suitable curing depth for high-fidelity printing, while thermal and microstructural characterization verified complete binder burnout and tetragonal phase formation. Metal infiltration increased capacitance and conductivity by approximately two and three orders of magnitude, respectively, compared to non-infiltrated lattices. The 25% solid-fraction FM infiltrated gyroid achieved the highest performance, exhibiting approximately 80 times greater capacitance, 8000 times higher conductivity, and 64% higher upper-bound piezoelectric power density than bulk BTO. These findings demonstrate that FM infiltration of architected piezoceramic lattices enables simultaneous improvement of charge storage, transport, and energy conversion figure of merit at the materials level, offering a promising materials platform to improve the processing-architecture-processing relationship, impacting future sensing, smart-infrastructure and energy-harvesting devices.