Simulation of a Hemispherical Chamber for Thermal Inkjet Printing.

It is crucial to improve printing frequency and ink droplet quality in thermal inkjet printing. This paper proposed a hemispherical chamber, and we used the CFD (computational fluid dynamics model) to simulate the inkjet process. During the whole simulation process, we first researched the hemispherical chamber's inkjet state equipped with straight, conical shrinkage, and conical diffusion nozzles. Based on the broken time and volume of the liquid column, the nozzle geometry of the hemispherical chamber was determined to be a conical shrinkage nozzle with a specific size of 15 µm in height and 15 µm in diameter at the top, and 20 µm in diameter at the bottom. Next, we researched the inkjet performance of the square chamber, the round chamber, and the trapezoidal chamber. The round chamber showed the best inkjet performance using 1.8 µs as the driving time and 10 MPa as the maximum bubble pressure. After that, we compared the existing thermal inkjet printing heads. The results showed that the hemispherical chamber inkjet head had the best performance, achieving 30 KHz high-frequency printing and having the most significant volume ratio of droplet to the chamber, reaching 14.9%. As opposed to the current 15 KHz printing frequency of the thermal inkjet heads, the hemispherical chamber inkjet head has higher inkjet performance, and the volume ratio between the droplet and the chamber meets the range standard of 10-15%. The hemispherical chamber structure can be applied to thermal inkjet printing, office printing, 3D printing, and bio-printing.

Design of Chopsticks-Shaped Heating Resistors for a Thermal Inkjet: Based on TaN Film.

Efficient printing frequency is critical for thermal bubble inkjet printing, while the difficulty lies in the structural design and material selection of the heating resistors. In this paper, a TaN film was used as the main material of the heating resistors, and two TaN films were placed in parallel to form the chopsticks-shaped structure. The heating time was divided into two sections, in which 0-0.1 µs was the preheating and 1.2-1.8 µs was the primary heating. At 1.8 µs, the maximum temperature of the Si3N4 film could reach about 1100 °C. At the same time, the SiO2 film was added between the TaN film and Si3N4 film as a buffer layer, which effectively avoided the rupture of the Si3N4 film due to excessive thermal stress. Inside the inkjet print head, the maximum temperature of the chamber reached about 680 °C at 2.5 µs. Due to the high power of the heating resistors, the working time was greatly reduced and the frequency of the inkjet printing was effectively increased. At the interface between the back of the chip and the cartridge, the SiO2 film was used to connect to ensure a timely ink supply. Under the condition of 12 V at 40 kHz, the inkjet chip could print efficiently with 10 nozzles at the same time. The inkjet chip proposed in this paper is not limited to only office printing, but also provides a new reference for 3D printing, cell printing, and vegetable and fruit printing.

A Multilayer Interlaced Ag Nanosheet Film Prepared by an Electrodeposition Method on a PPy@PEDOT:PSS Film: A Strategy to Prepare Sensitive Surface-Enhanced Raman Scattering Substrates.

A highly sensitive multilayer interlaced silver (Ag) nanosheet (MISN) film was prepared on a PPy@PEDOT:PSS film via an electrodeposition method for surface-enhanced Raman scattering (SERS) applications. After the PPy@PEDOT:PSS film was pretreated with ascorbic acid solution, many sparse Ag nanoparticles (NPs) could be directly reduced on the surface of the PPy@PEDOT:PSS film in AgNO3 solution. Then, the MISN film was directionally grown along the surface of sparse Ag NPs by using an electrochemical galvanostatic method to form a Ag/PPy@PEDOT:PSS film for a SERS substrate. The results indicated that with the increase in electrodeposition time, the density of Ag nanosheets was also increased for boosting the SERS effect. Accordingly, owing to the directional growth of Ag NPs, the increase in the length-width ratio of single Ag nanosheets would further promote the SERS signal of the substrate. Moreover, the maximum enhancement factor of the SERS substrate could reach to 12,478, and the minimum limit of detection of melamine solution was down to 5.42 ng/mL. The SERS sensitivity of the Ag nanosheet film reached 100.65. This method of preparing the SERS substrate provides a novel and robust strategy for the low-cost and high-sensitivity detection in biomedicine, drugs, and food.

Design of H-Shape Chamber in Thermal Bubble Printer.

The utilization rate of ink liquid in the chamber is critical for the thermal bubble inkjet head. The difficult problem faced by the thermal bubble inkjet printing is how to maximize the use of ink in the chamber and increase the printing frequency. In this paper, by adding a flow restrictor and two narrow channels into the chamber, the H-shape flow-limiting structure is formed. At 1.8 µs, the speed of bubble expansion reaches the maximum, and after passing through the narrow channel, the maximum reverse flow rate of ink decreased by 25%. When the vapor bubble disappeared, the ink fills the nozzle slowly. At 20 µs, after passing through the narrow channel, the maximum flow rate of the ink increases by 39%. The inkjet printing frequency is 40 kHz, and the volume of the ink droplet is about 13.1 pL. The structure improves the frequency of thermal bubble inkjet printing and can maximize the use of liquid in the chamber, providing a reference for cell printing, 3D printing, bioprinting, and other fields.

Improved Weighted Non-Local Mean Filtering Algorithm for Laser Image Speckle Suppression.

Laser speckle noise caused by coherence between lasers greatly influences the produced image. In order to suppress the effect of laser speckles on images, in this paper we set up a combination of a laser-structured light module and an infrared camera to acquire laser images, and propose an improved weighted non-local mean (IW-NLM) filtering method that adopts an SSI-based adaptive h-solving method to select the optimal h in the weight function. The analysis shows that the algorithm not only denoises the laser image but also smooths pixel jumps in the image, while preserving the image details. The experimental results show that compared with the original laser image, the equivalent number of looks (ENL) index of the IW-NLM filtered image improved by 0.80%. The speckle suppression index (SSI) of local images dropped from 4.69 to 2.55%. Compared with non-local mean filtering algorithms, the algorithm proposed in this paper is an improvement and provides more accurate data support for subsequent image processing analysis.