| The prevalence of heart valve disease is 3.8% in china,about 25 million residents suffering from heart valve disease.Surprisingly,prevalence of the elder over75 years old is as high as 13.3%.With the aging of social population,the risk of heart valve disease for the middle-aged and elderly people was increasingly terrible.Although the surgery of mechanical heart valve replacement is the most effective treatment at present,there exists some problems in the artificial heart valve such as poor biocompatibility,easy thrombosis,poor durability and lifelong use of anticoagulants.Therefore,it is urgent for us to make the research on artificial heart valves materials about anti-adhesion and self-cleaning.Inspired by the typical hydrophobic surface in nature including lotus and combining medical and industrial research concepts,the design of bionic superhydrophobic self-cleaning surface,the study of wettability-related size effect,the preparation of cross-scale composite structure as well as the design of an extracorporeal circulation test system were carried out.The main contents and conclusions are as follows:1.Based on the characteristics of the typical animal heart valve structures,bionic array microstructures were constructed and the contact angles of droplets in the Wenzel and Cassie states on the corresponding surface were calculated.And the superhydrophobic uneven composite structure sequence was built in the order of decreasing contact angles.Droplets could spontaneously move from areas with large contact angles to areas with small contact angles for different surface tension.Therefore,droplets could complete not only the directional movement but also automatically rolling off in the set direction and the function of the surface self-cleaning could be achieved under the Marangoni effect of surface tension changing by the dual gradients of structural gradient and temperature gradient.2.The surface array microstructures were fabricated on the materials of brass and copper by LS-WEDM and the wettability characteristics were studied.It was revealed that the different droplet relative dimension on the diversity structures and materials exhibited the wettability size effect.Specifically,the effects of droplet relative dimension could be divided into two stages.Lower than 208.6,the CAs gradually decreased with the increasing of the droplet relative dimension.Based on a relatively larger droplet relative dimension larger than 178.8,the CAs exhibited an irregular variation tendency.Regarding the droplet bouncing behaviors,the period times were shortened gradually as the droplet relative dimensions decreased indicating that the droplets with large relative sizes were more difficult to overcome the adhesion of the array structure.When the droplet relative dimension increased to 13.5,the capillary force generated by the surface with more surface energy was not enough to counteract the gravity.Therefore,the whole period time became shorter on account of the less time required to get rid of the interaction between solid and liquid phases.3.The titanium alloys and high-entropy alloys were ablated by Nano-second laser with the distance of 50 ?m and 100 ?m.Besides,“micro column-micro protrusionsnanoparticle-fluorinated layer” cross-scale structures were obtained after 4h heat treatment,0.5h-4h fluorination treatment and composite treatment and the wettability-related were studied.It was found that the contact angles were greatly reduced through prolonged surface fluorination treatment and the wettability of metal surfaces processed by the fluorination treatment followed by heat treatment were improved in comparison to fluorination treatment alone.Moreover,there were highly cross-linked structures between the micropillars with a space of 50 ?m,which made the solid-liquid contact state change from the Cassie state to the Wenzel state.Meanwhile,droplet bouncing of five times appeared on the surface of the cross-linked structure after composite treatment.The fluorinated layer was partially cover the micro protrusions and nanoparticle.Therefore,a gap was formed between the organic adsorption layer and the fluorinated layer,which acted as a “mechanical spring”during the continuous droplet bouncing processes.In addition,the contact time significantly increased as a function of numbers of droplet bounces.The contact times of droplet bounce increased monotonically from 10.1 ms to 15.6 ms.4.Based on the service microenvironment of the artificial heart valve in the body,the extracorporeal circulating test system close to actual service conditions was built to study the wettability and self-clean properties of the biomimetic artificial heart valve materials.Porcine plasma was selected to construct the physiological environment of the blood system and a specific flow of circulating plasma medium was supplied to the valve material through a fluid pump.Meanwhile,the relay acquired square wave signal with a frequency of 1 Hz by the signal generator to simulate the regular beating of the heart.Thus,the adhesion and coagulation behaviors of proteins on the materials were in-situ observed with the use of optical microscopy on the test components fabricated by photocuring 3D printing machine during the study of wettability and self-clean properties. |
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