自供能柔性氧化石墨烯湿度传感器的喷墨印刷制备及性能研究

呼吸频率及呼吸模式检测可用于医疗诊断以及人体健康评估。传统的医学检测器件体积大、能耗高、使用不便捷。针对高性能、低成本、便携式电子产品的迫切需求, 本工作利用氧化石墨烯材料自发极化后对湿度敏感的特性, 通过喷墨印刷方法制备了一种可以实现自供能的平面型湿度传感器。所制备的传感器对湿度响应呈现为线性关系, 并且具有优异的灵敏度、快速响应和恢复特性、多次循环稳定性和长期老化稳定性等特性。基于该传感器可以实现对于人体呼吸频率和呼吸模式等的检测。制备的湿度传感器具有制作简单、成本低、不易受人体行动及外界环境干扰等优点, 适用于实时监测呼吸频率和呼吸模式。     

Fiber-Optic Photoacoustic Generator Realized by Inkjet-Printing of CNT-PDMS Composites on Fiber End Faces

In recent years, photoacoustic generators based on multiwalled carbon nanotubes (MWCNT) and polydimethylsiloxane (PDMS) are manufactured in a variety of ways, which influences the properties of the generators with respect to frequency bandwidth, sound wave pressure, robustness, and reproducibility. Due to the high optical absorption of MWCNTs and the high thermal expansion coefficient of PDMS, this combination is ideally suited for use as a photoacoustic generator. This study presents a novel method to produce photoacoustic generators based on long-term stable MWCNT and PDMS inks with a high reproducibility by means of inkjet-printing. The MWCNT-PDMS layers (thicknesses of 2–4 µm), printed directly onto the distal end face of a multimode glass fiber, show a good homogeneity and low optical transmission (19–21%). After the preparation of the fiber pieces, the inkjet printer performs all steps automatically in a time period of 30–60 s per layer. The generated ultrasonic pressure (0.39–0.54 MPa) and frequency bandwidth (1.5–12.7 MHz) can be measured at a distance of ≈4 mm with a laser fluency of 12.7 mJ cm⁻². These highly reproducible printed photoacoustic generators can be well used for nondestructive material testing and medical applications.     

Effect of print path process on sintering behavior and thermal shock resistance of Al2O3 ceramics fabricated by 3D inkjet-printing

In this study, Al₂O₃ ceramics parts were printed by inkjet printing technology with different printed paths distributions, such as the spiral printed path, round trip straight printed path and ladder lap printed path. The influences of inkjet printed paths on sintering performance and thermal shock resistance of the Al₂O₃ green bodies were investigated. The sintering performance of the green sample with the ladder lap printed path is the highest among the three samples. Sintered at 1550?℃, its bulk density and porosity reached 3.73?g/cm³ and 10.80%, respectively. In addition, the thermal shock resistance of the sample with the step print path reached 11 times. The results suggest that the optimization of the printed path provides an effective way to print 3D ceramics with good performances through 3D inkjet-printing technology.