3D printing has revolutionized manufacturing across various sectors. While methods like fused deposition modeling (FDM) are widely used, they often lack the high resolution offered by photocuring techniques such as stereolithography (SLA) and digital light processing (DLP). However, these photocuring methods rely on complex and bulky mechanical systems that limit speed, portability, and material complexity. The paper highlights the limitations of current 3D printing technologies, emphasizing the need for a compact, portable, and low-cost alternative. Silicon photonics, with its ability to create compact, cost-effective, and high-performance optical microsystems using scalable CMOS fabrication, is presented as a potential solution. Integrated optical phased arrays, capable of non-mechanical light beam steering, are identified as a key enabling technology. The research aims to combine silicon photonics and photochemistry to create a chip-based 3D printer, eliminating the need for moving parts and significantly improving portability and cost-effectiveness.

The introduction provides a comprehensive overview of existing 3D printing technologies, comparing extrusion-based methods (like FDM) with photocuring techniques (SLA, DLP, MSLA). The limitations of current methods, including bulky mechanical systems impacting portability, resolution, print speed, and material complexity, are clearly articulated. The review highlights the research efforts toward volumetric 3D printing to address these limitations, but notes the persistence of bulky mechanical systems in these advanced approaches. The paper emphasizes the potential of silicon photonics and integrated optical phased arrays to overcome these limitations, arguing that the existing literature lacks any application of these technologies to 3D printing, making this research novel.

The paper proposes a chip-based 3D printer comprising a millimeter-scale silicon photonics chip at the bottom of a stationary well containing visible-light-curable resin. The chip projects reconfigurable visible-light holograms to selectively solidify the resin, creating the 3D object. Key components include a liquid resin designed for visible-light curing (as opposed to the typical UV-activated resins), a 2D grid of on-chip visible-light integrated optical phased arrays to act as the aperture's pixels, and integrated modulators to control the amplitude and phase of light emitted by each pixel. The system uses silicon nitride waveguides due to their low absorption in the visible spectrum and CMOS compatibility. To overcome the limitations of silicon nitride's low thermo-optic coefficient, liquid crystal material with strong birefringence is integrated to enable dynamic modulation. Heterogeneous integration with a CMOS electronics chip is proposed for control. The proof-of-concept uses a visible-light integrated optical phased array with a liquid-crystal-based cascaded-phase-shifter architecture. A custom three-component photosystem-based resin is developed for efficient visible-light curing (637 nm wavelength). The experimental setup involves a fabricated and packaged photonic chip, a sample stage with resin wells, and a 637 nm diode laser. The beam emitted by the array is characterized, and the system is used to print voxels and patterns in one and two dimensions. The curing rate is characterized by measuring voxel size as a function of curing time.

The research successfully demonstrated the first chip-based 3D printing system. A stereolithography-inspired version of the proposed system was experimentally realized using a visible-light integrated optical phased array and a custom visible-light-curable resin. The system successfully printed sub-millimeter-scale voxels within seconds, demonstrating the feasibility of rapid, high-resolution printing. The non-mechanical beam steering capability of the optical phased array was used to print lines in one dimension and arbitrary patterns in two dimensions without any moving parts. The experimental results closely matched simulations, validating the design and functionality of the integrated optical phased array. The custom visible-light-curable resin proved effective, with a curing process simple enough to be performed outside of a specialized chemistry laboratory environment.

The successful demonstration of the chip-based 3D printer represents a significant step towards creating compact, portable, and low-cost 3D printing systems. The results confirm the potential of silicon photonics and integrated optical phased arrays for revolutionizing 3D printing technology. The elimination of complex mechanical systems simplifies the design and increases portability, while the rapid curing of the custom resin enhances print speed. The ability to print arbitrary patterns in two dimensions opens possibilities for creating more intricate and complex objects. The work addresses the need for advanced 3D-printing technology by offering a highly compact and low-cost solution.

This paper presents the first chip-based 3D printer, combining silicon photonics and photochemistry. The proof-of-concept demonstrated the successful printing of sub-millimeter voxels and 2D patterns using a visible-light integrated optical phased array and a custom resin. Future work will focus on extending this technology to full 3D volumetric printing, optimizing the resin for improved properties, and integrating the CMOS electronics for complete system control.

The current proof-of-concept demonstrates 2D printing; scaling up to full 3D volumetric printing requires further development. The resolution and printing speed could be further optimized by improving the design and performance of the optical phased array and resin. The current system uses a single wavelength; expanding to multi-wavelength printing would enable the use of a wider range of materials. A full system integration with the CMOS electronics remains a future step.