EAGER: Carbon dioxide (CO2) microbubbles-based ultrasonically responsive pressure sensor

测量心脏腔内或心血管系统其他特定部位的血压的能力对心脏病的早期诊断和治疗至关重要。理想情况下，这些测量应该是非侵入性的。测量压力的一种方法是向血液中注入非常小的气泡，直径约为一微米，称为“微气泡”。微泡的工作原理是在超声波的作用下迅速收缩和膨胀。膨胀和收缩的频率可以用来测量气泡附近的压力。然而，使用这种方法很难检测到压力的微小变化，这些变化可能是健康问题的信号。这个研究项目包括探索一种新的方案来覆盖这些气泡，使它们更稳定，对局部血压的变化更敏感。研究人员正在制作和描述一个涂层材料库，然后测试涂层将使气泡对周围压力的反应增强的想法。如果成功，这种方法可以在一系列超声诊断中使用涂层微泡。该研究项目还包括训练学生和青年研究人员使用实验方法，目前正在进行几项外联活动，包括为一般公众举办研究开放日和科学讲座。在这个项目中，研究人员正在开发结合微流体学、流变学、聚合物合成和石墨烯化学的方法，以生产和表征聚乙二醇-氧化石墨烯（PEG-GO）封装的二氧化碳微泡，并操纵它们的压力敏感性。该研究利用了最近在可交联的PEG-GO水凝胶的合成和流变学方面的工作，以及PEG-GO水凝胶涂层在控制微泡压力响应方面的作用。通过系统地改变PEG的分子量和每个GO的反应官能团的平均数量和类型，合成了具有不同性能的PEG-GO材料库。使用核磁共振光谱、红外光谱、热重分析、扫描电子显微镜、原子力显微镜和流变学方法对样品进行表征，以确定结构-性能关系。初步结果表明，水凝胶具有稳定二氧化碳微泡的作用。研究人员推测，随着环境压力的变化，涂层的渗透率会发生变化，从而对压力-气泡尺寸关系产生协同效应。这种修改应该产生气泡大小对压力变化的显著响应，这应该允许检测压力的非常小的变化。研究人员正在使用微流体平台来产生聚乙二醇-氧化石墨烯封装的二氧化碳气泡，然后使用成像技术来确定它们在压力变化下的溶解情况。

The ability to measure blood pressure inside the chambers of the heart or at other specific places in the cardiovascular system is essential to the early diagnosis and treatment of heart disease. Ideally, these measurements should be non-invasive. One approach to measuring pressure involves injecting very small gas bubbles, about one micrometer in diameter, called "microbubbles" into the blood. Microbubbles work by rapidly contracting and expanding in response to an ultrasound beam. The frequency of the expansion and contraction can be used to measure the pressure near the bubble. However, it is difficult to detect the very small changes in pressure that can signal health problems using this approach. This research project involves exploring a novel scheme for coating these bubbles to make them both more stable and more sensitive to changes in the local blood pressure. The researchers are making and characterizing a library of coating materials, and then testing the idea that the coatings will create an enhanced response of the bubble to the surrounding pressure. If successful, this approach could enable the use of coated microbubbles in a range of ultrasound diagnostics. The research project also involves training of students and young researchers in experimental methods, and several outreach activities are being pursued, including research open houses and science lectures for the general public. In this project researchers are developing approaches to combine microfluidics, rheology, polymer synthesis, and graphene chemistry to produce and characterize polyethylene glycol-graphene oxide (PEG-GO) encapsulated carbon dioxide microbubbles and to manipulate their pressure sensitivity. The research leverages recent work on the synthesis and rheology of cross-linkable PEG-GO hydrogels and on the role of the PEG-GO hydrogel coating in controlling the pressure response of the microbubbles. A library of PEG-GO materials with different properties are being synthesized by systematically varying the molecular weight of the PEG and the average number and type of reactive functional groups per GO. Samples are being characterized using nuclear magnetic resonance spectroscopy, infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, atomic force microscopy, and rheometry methods to determine structure-property relationships. Preliminary results suggest that the hydrogel will stabilize carbon dioxide microbubbles. The researchers hypothesize that the coating will produce a synergistic effect on the pressure-bubble size relationship through the variation of the coating permeability as the ambient pressure changes. This modification should produce a dramatic response of bubble size to pressure changes, which should allow detection of very small changes in pressure. The researchers are using microfluidic platforms to generate PEG-GO encapsulated carbon dioxide bubbles and then using imaging to determine their dissolution in response to pressure changes.