Search Results (8)

Vat photopolymerization (VPP) is an effective additive manufacturing (AM) process known for its high dimensional accuracy and excellent surface finish. It employs vector scanning and mask projection techniques to cure photopolymer resin at a specific wavelength. Among the mask projection methods, digital light processing (DLP) and liquid crystal display (LCD) VPP have gained significant popularity in various industries. To upgrade DLP and LCC VPP into a high-speed process, increasing both the printing speed and projection area in terms of the volumetric print rate is crucial. However, challenges arise, such as the high separation force between the cured part and the interface and a longer resin refilling time. Additionally, the divergence of the light-emitting diode (LED) makes controlling the irradiance homogeneity of large-sized LCD panels difficult, while low transmission rates of near ultraviolet (NUV) impact the processing time of LCD VPP. Furthermore, limitations in light intensity and fixed pixel ratios of digital micromirror devices (DMDs) constrain the increase in the projection area of DLP VPP. This paper identifies these critical issues and provides detailed reviews of available solutions, aiming to guide future research towards developing a more productive and cost-effective high-speed VPP in terms of the high volumetric print rate. Full article

The objective of this study was to present a methodology and manufacturing workflow for non-invasive ventilation interfaces (NIV) for neonates and small infants. It aimed to procure a fast and feasible solution for personalized NIV produced in-house with the aim of improving fit and comfort for the patient. Three-dimensional scans were obtained by means of an intraoral (Trios 3) and a facial scanner (3dMd Flex System). Fusion 360 3D-modelling software was employed to automatize the design of the masks and their respective casting molds. These molds were additively manufactured by stereolithography (SLA) and fused filament fabrication (FFF) technologies. Silicone was poured into the molds to produce the medical device. In this way, patient individualized oronasal and nasal masks were produced. An automated design workflow and use of additive manufacturing enabled a fast and feasible procedure. Despite the cost for individualization likely being higher than for standard masks, a user-friendly workflow for in-house manufacturing of these medical appliances proved to have potential for improving NIV in neonates and infants, as well as increasing comfort. Full article

In the process of digital micromirror device (DMD) digital mask projection lithography, the lithography efficiency will be enhanced greatly by path planning of pattern transfer. This paper proposes a new dual operator and dual population ant colony (DODPACO) algorithm. Firstly, load operators and feedback operators are used to update the local and global pheromones in the white ant colony, and the feedback operator is used in the yellow ant colony. The concept of information entropy is used to regulate the number of yellow and white ant colonies adaptively. Secondly, take eight groups of large-scale data in TSPLIB as examples to compare with two classical ACO and six improved ACO algorithms; the results show that the DODPACO algorithm is superior in solving large-scale events in terms of solution quality and convergence speed. Thirdly, take PCB production as an example to verify the time saved after path planning; the DODPACO algorithm is used for path planning, which saves 34.3% of time compared with no path planning, and is about 1% shorter than the suboptimal algorithm. The DODPACO algorithm is applicable to the path planning of pattern transfer in DMD digital mask projection lithography and other digital mask lithography. Full article

With medium wave infrared (MWIR) focal plane array-based (FPA) compressive imaging (CI), high-resolution images can be obtained with a low-resolution MWIR sensor. However, restricted by the size of digital micro-mirror devices (DMD), aperture interference is inevitable. According to the system model of FPA CI, aperture interference aggravates the blocky structural artifacts (BSA) in the reconstructed images, which reduces the image quality. In this paper, we propose a novel DMD mask design strategy, which can effectively suppress BSA and maximize the reconstruction efficiency. Compared with random binary codes, the storage space and computation cost can be significantly reduced. Based on the actual MWIR FPA CI system, we demonstrate the proposed DMD masks can effectively suppress the BSA in the reconstructed images. In addition, a new evaluation index, blocky root mean square error, is proposed to indicate the BSA in FPA CI. Full article

In the Hadamard transform (HT) near-infrared (NIR) spectrometer, there are defects that can create a nonuniform distribution of spectral energy, significantly influencing the absorbance of the whole spectrum, generating stray light, and making the signal-to-noise ratio (SNR) of the spectrum inconsistent. To address this issue and improve the performance of the digital micromirror device (DMD) Hadamard transform near-infrared spectrometer, a split waveband scan mode is proposed to mitigate the impact of the stray light, and a new Hadamard mask of variable-width stripes is put forward to improve the SNR of the spectrometer. The results of the simulations and experiments indicate that by the new scan mode and Hadamard mask, the influence of stray light is restrained and reduced. In addition, the SNR of the spectrometer also is increased. Full article

A maskless lithography method to realize the rapid and cost-effective fabrication of micro-optics elements with arbitrary surface profiles is reported. A digital micro-mirror device (DMD) is applied to flexibly modulate that the exposure dose according to the surface profile of the structure to be fabricated. Due to the fact that not only the relationship between the grayscale levels of the DMD and the exposure dose on the surface of the photoresist, but also the dependence of the exposure depth on the exposure dose, deviate from a linear relationship arising from the DMD and photoresist, respectively, and cannot be systemically eliminated, complicated fabrication art and large fabrication error will results. A method of compensating the two nonlinear effects is proposed that can be used to accurately design the digital grayscale mask and ensure a precise control of the surface profile of the structure to be fabricated. To testify to the reliability of this approach, several typical array elements with a spherical surface, aspherical surface, and conic surface have been fabricated and tested. The root-mean-square (RMS) between the test and design value of the surface height is about 0.1 μm. The proposed method of compensating the nonlinear effect in maskless lithography can be directly used to control the grayscale levels of the DMD for fabricating the structure with an arbitrary surface profile. Full article

Fabrication of hydrogel microstructures has attracted considerable attention. A large number of applications, such as fabricating tissue engineering scaffolds, delivering drugs to diseased tissue, and constructing extracellular matrix for studying cell behaviors, have been introduced. In this article, an ultraviolet (UV)-curing method based on a digital micromirror device (DMD) for fabricating poly(ethylene glycol) diacrylate (PEGDA) hydrogel microstructures was presented. By controlling UV projection in real-time using a DMD as digital dynamic mask instead of a physical mask, polymerization of the pre-polymer solution could be controlled to create custom-designed hydrogel microstructures. Arbitrary microstructures could also be fabricated within several seconds (<5 s) using a single-exposure, providing a much higher efficiency than existing methods, while also offering a high degree of flexibility and repeatability. Moreover, different cell chains, which can be used for straightforwardly and effectively studying the cell interaction, were formed by fabricated PEGDA microstructures. Full article

We report in this paper a novel, inexpensive and flexible method for fabricating micrometer- and nanometer-scale three-dimensional (3D) polymer structures using visible light sources instead of ultra-violet (UV) light sources or lasers. This method also does not require the conventional micro-photolithographic technique (i.e., photolithographic masks) for patterning and fabricating polymer structures such as hydrogels. The major materials and methods required for this novel fabrication technology are: (1) any cross-linked network of photoactive polymers (examples of fabricated poly(ethylene glycol) (PEG)-diacrylate hydrogel structures are shown in this paper); (2) an Optically-induced Dielectrophoresis (ODEP) System which includes an “ODEP chip” (i.e., any chip that changes its surface conductivity when exposed to visible light), an optical microscope, a projector, and a computer; and (3) an animator software hosted on a computer that can generate virtual or dynamic patterns which can be projected onto the “ODEP chip” through the use of a projector and a condenser lens. Essentially, by placing a photosensitive polymer solution inside the microfluidic platform formed by the “ODEP chip” bonded to another substrate, and applying an alternating current (a.c.) electrical potential across the polymer solution (typically ~20 V_p-p at 10 kHz), solid polymer micro/nano structures can then be formed on the “ODEP chip” surface when visible-light is projected onto the chip. The 2D lateral geometry (x and y dimensions) and the thickness (height) of the micro/nano structures are dictated by the image geometry of the visible light projected onto the “ODEP chip” and also the time duration of projection. Typically, after an image projection with intensity ranging from ~0.2 to 0.4 mW/cm² for 10 s, ~200 nm high structures can be formed. In our current system, the thickness of these polymer structures can be controlled to form from ~200 nanometers to ~3 micrometers structures. However, in the in-plane dimensions, only ~7 μm resolution can be achieved now, due to the optical diffraction limit and the physical dimensions of DMD mirrors in the projector. Nevertheless, with higher quality optical components, the in-plane resolution is expected to be sub-micron. Full article