RESUMEN
Electric field-assisted fused deposition modeling (E-FDM) is a promising technique in the field of 3D printing. This paper studies the start-up stage of the printing, which is a process of liquid gradually deforming and making an initial contact with the substrate under the action of electric stress. Polycaprolactone, a popular material for biomedicine, is selected as the printing material. With a home-built E-FDM system, the nozzle-to-substrate distance and the nozzle and substrate temperatures are all held steady. With a photography system, the process of meniscus deformation is recorded. And by image processing methods, the meniscus length and the volume of liquid at the nozzle can be obtained. At a set of initial liquid volumes (V i), nozzle voltage is ramped to a fixed value at a fixed rate. The effects of V i on the meniscus deformation during the start-up stage of the printing are examined. For sufficiently small V i, the meniscus deforms into a conical (Taylor cone) shape, and a fine jet with a diameter much smaller than the nozzle diameter appears. For sufficiently large V i, the meniscus exhibits a spindle shape when it touches the substrate. At an intermediate V i, a Taylor cone is formed, tending to eject a fine jet. After a short period of stagnation or even a slight retraction, no liquid is emitted. Through this study, it is suggested that for high-resolution printing, ramping the voltage at small V i may be preferable. This proposition is preliminarily confirmed in a direct writing test.
RESUMEN
Gastric cancer is the most common gastrointestinal cancer in China. The morbidity and mortality are extremely high and there are significant challenges in the treatment of gastric cancer. Recent studies have shown that the expressions of T lymphocyte subsets vary in the immune microenvironment of gastric cancer patients. T lymphocytes are not only the main effector cells of human cellular immunity, but also the important immunoregulatory cells. T lymphocytes not only reflect the state of the tumor microenvironment, but also closely relate with the prognosis of patients. T lymphocytes play a crucial guiding role in the clinical treatment. Currently, clinical trials related to immunological checkpoint inhibitors are still underway, among which PD-1/PD-L1 monoclonal antibody has been approved for the treatment of gastric cancer. The applications of tumor vaccines and adoptive cell therapies in gastric cancer are also being explored. How to screen patients suitable to immunotherapy, develop the best combination therapy and evaluate the effectiveness of immunotherapy need to be studied and solved.