Extrusion-based cell deposition has become a prominent technique for expanding bioprinting applications.However,the associated print resolution in the order of nanolitre or above has been a limiting factor.The demand ...Extrusion-based cell deposition has become a prominent technique for expanding bioprinting applications.However,the associated print resolution in the order of nanolitre or above has been a limiting factor.The demand for improving print resolution towards the scale of a single cell has driven the development of precision nozzle extrusion,although the benefits gained remain ambiguous.Here,aided by in situ imaging,we investigated the dynamics of cell organisation through an extrusion-based microcapillary tip with picolitre precision through in-air or immersion deposition.The microcapillary extrusion setup,termed‘Picodis’,was demonstrated by generating droplets of colouring inks immersed in an immiscible medium.Next,using 3T3 fibroblast cells as an experimental model,we demonstrated the deposition of cell suspension,and pre-aggregated cell pellets.Then,the dynamic organisation of cells within the microcapillary tip was described,along with cell ejection and deposition upon exiting the tip opening.The vision-assisted approach revealed that when dispersed in a culture medium,the movements of cells were distinctive based on the flow profiles and were purely driven by laminar fluid flow within a narrow tip.The primary process limitations were cell sedimentation,aggregation and compaction,along with trapped air bubbles.The use of picolitre-level resolution microcapillary extrusion,although it provides some level of control for a small number of cells,does not necessarily offer a reliable method when a specified number of cells are required.Our study provides insights into the process limitations of high-resolution cell ink extrusion,which may be useful for optimising biofabrication processes of cell-laden constructs for biomedical research.展开更多
An accelerating charged particle exerts a force upon itself. If we model the particle as a spherical shell of radius R, and calculate the force of one piece of this shell on another and eventually integrate over the w...An accelerating charged particle exerts a force upon itself. If we model the particle as a spherical shell of radius R, and calculate the force of one piece of this shell on another and eventually integrate over the whole particle, there will be a net force on the particle due to the breakdown of Newton’s third law. This symmetry breaking mechanism relies on the finite size of the particle;thus, as Feynman has stated, conceptually this mechanism doesn’t make good sense for point particles. Nonetheless, in the point particle limit, two terms survive in the self-force series: R0 and R-1 terms. The R0 term can alternatively be attributed to the well-known radiation reaction but the origin of R-1 term is not clear. In this study, we will show that this new term can be accounted for by an inductive mechanism in which the changing magnetic field induces an inductive force on the particle. Using this inductive mechanism, we derive R-1 term in an extremely easy way.展开更多
基金supported by the European Research Council(ERC-St G,758865,to YYSH)the financial support from the W.D.Armstrong Trust and the Macao Postgraduate Scholarship Fund。
文摘Extrusion-based cell deposition has become a prominent technique for expanding bioprinting applications.However,the associated print resolution in the order of nanolitre or above has been a limiting factor.The demand for improving print resolution towards the scale of a single cell has driven the development of precision nozzle extrusion,although the benefits gained remain ambiguous.Here,aided by in situ imaging,we investigated the dynamics of cell organisation through an extrusion-based microcapillary tip with picolitre precision through in-air or immersion deposition.The microcapillary extrusion setup,termed‘Picodis’,was demonstrated by generating droplets of colouring inks immersed in an immiscible medium.Next,using 3T3 fibroblast cells as an experimental model,we demonstrated the deposition of cell suspension,and pre-aggregated cell pellets.Then,the dynamic organisation of cells within the microcapillary tip was described,along with cell ejection and deposition upon exiting the tip opening.The vision-assisted approach revealed that when dispersed in a culture medium,the movements of cells were distinctive based on the flow profiles and were purely driven by laminar fluid flow within a narrow tip.The primary process limitations were cell sedimentation,aggregation and compaction,along with trapped air bubbles.The use of picolitre-level resolution microcapillary extrusion,although it provides some level of control for a small number of cells,does not necessarily offer a reliable method when a specified number of cells are required.Our study provides insights into the process limitations of high-resolution cell ink extrusion,which may be useful for optimising biofabrication processes of cell-laden constructs for biomedical research.
文摘An accelerating charged particle exerts a force upon itself. If we model the particle as a spherical shell of radius R, and calculate the force of one piece of this shell on another and eventually integrate over the whole particle, there will be a net force on the particle due to the breakdown of Newton’s third law. This symmetry breaking mechanism relies on the finite size of the particle;thus, as Feynman has stated, conceptually this mechanism doesn’t make good sense for point particles. Nonetheless, in the point particle limit, two terms survive in the self-force series: R0 and R-1 terms. The R0 term can alternatively be attributed to the well-known radiation reaction but the origin of R-1 term is not clear. In this study, we will show that this new term can be accounted for by an inductive mechanism in which the changing magnetic field induces an inductive force on the particle. Using this inductive mechanism, we derive R-1 term in an extremely easy way.
