Extrusion-based 3D bioprinting is a direct deposition approach used to create three-dimensional(3D)tissue scaffolds typically comprising hydrogels.Hydrogels are hydrated polymer networks that are chemically or physica...Extrusion-based 3D bioprinting is a direct deposition approach used to create three-dimensional(3D)tissue scaffolds typically comprising hydrogels.Hydrogels are hydrated polymer networks that are chemically or physically cross-linked.Often,3D bioprinting is performed in air,despite the hydrated nature of hydrogels and the potential advantage of using a liquid phase to provide cross-linking and otherwise functionalize the hydrogel.In this work,we print gelatin alginate hydrogels directly into a cross-linking solution of calcium chloride and investigate the influence of nozzle diameter,distance between nozzle and surface,calcium chloride concentration,and extrusion rate on the dimensions of the printed hydrogel.The hydrogel layer height was generally found to increase with increasing extrusion rate and nozzle distance,according to the increased volume extruded and the available space,respectively.In addition,the hydrogel width was generally found to increase with decreasing nozzle distance and cross-linking concentration corresponding to confinement-induced spreading and low crosslinking regimes,respectively.Width/height ratios of^1 were generally achieved when the nozzle diameter and distance were comparable above a certain cross-linking concentration.Using these relationships,biocompatible 3D multilayer structures were successfully printed directly into calcium chloride cross-linking solution.展开更多
Atomic force microscopy(AFM)-based electrochemical etching of a highly oriented pyrolytic graphite(HOPG)surface is studied toward the single-atomic-layer lithography of intricate patterns.Electrochemical etching is pe...Atomic force microscopy(AFM)-based electrochemical etching of a highly oriented pyrolytic graphite(HOPG)surface is studied toward the single-atomic-layer lithography of intricate patterns.Electrochemical etching is performed in the water meniscus formed between the AFM tip apex and HOPG surface due to a capillary effect under controlled high relative humid-ity(~75%)at otherwise ambient conditions.The conditions to etch nano-holes,nano-lines,and other intricate patterns are investigated.The clectrochemical reactions of HOPG etching should not generatc debris duc to the conversion of graphite to gaseous CO and CO_(2)based on etching reactions.However,debris is observed on the etched HOPG surface,and incom-plete gasification of carbon occurs during the etching process,resulting in the generation of solid intermediates.Moreover,the applied potential is of critical importance for precise etching,and the precision is also significantly influenced by the AFM tip wear.This study shows that the AFM-based electrochemical etching has the potential to remove the material in a single-atomic-layer precision.This result is likely because the etching process is based on anodic dissolution,resulting in the material removal atom by atom.展开更多
Manufacturing at the atomic scale is the next generation of the industrial revolution.Atomic and close-to-atomic scalemanufacturing(ACSM)helps to achieve this.Atomic force microscopy(AFM)is a promising method for this...Manufacturing at the atomic scale is the next generation of the industrial revolution.Atomic and close-to-atomic scalemanufacturing(ACSM)helps to achieve this.Atomic force microscopy(AFM)is a promising method for this purposesince an instrument to machine at this small scale has not yet been developed.As the need for increasing the number ofelectronic components inside an integrated circuit chip is emerging in the present-day scenario,methods should be adoptedto reduce the size of connections inside the chip.This can be achieved using molecules.However,connecting moleculeswith the electrodes and then to the external world is challenging.Foundations must be laid to make this possible for thefuture.Atomic layer removal,down to one atom,can be employed for this purpose.Presently,theoretical works are beingperformed extensively to study the interactions happening at the molecule-electrode junction,and how electronic transportis affected by the functionality and robustness of the system.These theoretical studies can be verified experimentally only if nano electrodes are fabricated.Silicon is widely used in the semiconductor industry to fabricate electronic components.Likewise,carbon-based materials such as highly oriented pyrolytic graphite,gold,and silicon carbide find applications inthe electronic device manufacturing sector.Hence,ACSM of these materials should be developed intensively.This paperpresents a review on the state-of-the-art research performed on material removal at the atomic scale by electrochemical andmechanical methods of the mentioned materials using AFM and provides a roadmap to achieve effective mass productionof these devices.展开更多
The realization of a mixed-phase microstructure in strained BiFeO_(3)(BFO)thin films has led to numerous novel effects derived from the coexistence of the tetragonal-like monoclinic phase(T phase)and rhombohedral-like...The realization of a mixed-phase microstructure in strained BiFeO_(3)(BFO)thin films has led to numerous novel effects derived from the coexistence of the tetragonal-like monoclinic phase(T phase)and rhombohedral-like monoclinic phase(R phase).Strong strain and polarization diiferences between the phases should result in a high level of transformation plasticity,which enables the continuous alteration of the relative proportion of R and T states in response to external forces.Although the potential for utilizing such plasticity to control mixed-phase populations under external stimuli is evident,direct experi・mental evidence backed by equilibrium predictions has not yet been fully demonstrated.Here we demonstrate deterministic control of mixed-phase populations in an epitaxially strained BFO thin film through the application of localized stresses and electric fields in a reversible manne匚The results illustrate and rationalize deterministic control of mixed phases in strained BFO films,which could be crucial in tuning their functional properties.The findings also highlight a new multiparametric technique in the scanning probe lithography toolbox based on tip-assisted electric and strain field manipulation of functional properties that might find application beyond the ferroelectric domain and structural phase lithography.展开更多
Scanning probe microscopy(SPM)and atomic force microscopy(AFM)are widely used for surface imaging and characterization,combining nano-to atomic-scale precision with highly sensitive force measurements.Thus,AFM is cons...Scanning probe microscopy(SPM)and atomic force microscopy(AFM)are widely used for surface imaging and characterization,combining nano-to atomic-scale precision with highly sensitive force measurements.Thus,AFM is considered an enabling technology,impacting many scientific fields,including life and materials sciences.In addition to mapping interaction forces,AFM can be used for the precise application of forces(controlling both location and magnitude),in combination with the application of electrical bias and controlled environments.Moreover,when combined with advances in nanoscale probe technology,SPM-based nanofabrication enables state-of-the-art nanomanufacturing at interfaces.展开更多
基金the Ministry of Higher Education of Saudi Arabia under the King Abdullah Scholarship Program(IR10133)Enterprise Ireland(CF-2016-0389-P)+2 种基金the European Union’sHorizon 2020 research and innovation program under Marie Sklodowska-Curie Grant Agreement No.644175Science Foundation Ireland(13/TIDA/B2701)This project was co-funded by the European Regional Development Fund(ERDF)under Ireland’s European Structural and Investment Funds Programmes 2014–2020.
文摘Extrusion-based 3D bioprinting is a direct deposition approach used to create three-dimensional(3D)tissue scaffolds typically comprising hydrogels.Hydrogels are hydrated polymer networks that are chemically or physically cross-linked.Often,3D bioprinting is performed in air,despite the hydrated nature of hydrogels and the potential advantage of using a liquid phase to provide cross-linking and otherwise functionalize the hydrogel.In this work,we print gelatin alginate hydrogels directly into a cross-linking solution of calcium chloride and investigate the influence of nozzle diameter,distance between nozzle and surface,calcium chloride concentration,and extrusion rate on the dimensions of the printed hydrogel.The hydrogel layer height was generally found to increase with increasing extrusion rate and nozzle distance,according to the increased volume extruded and the available space,respectively.In addition,the hydrogel width was generally found to increase with decreasing nozzle distance and cross-linking concentration corresponding to confinement-induced spreading and low crosslinking regimes,respectively.Width/height ratios of^1 were generally achieved when the nozzle diameter and distance were comparable above a certain cross-linking concentration.Using these relationships,biocompatible 3D multilayer structures were successfully printed directly into calcium chloride cross-linking solution.
基金The authors would like to thank the support received from the Science Foundation Ireland(SFI)(No.15/RP/B3208)‘111’project by the State Administration of Foreign Experts Affairs and the Ministry of Education of China(No.B07014)+2 种基金the National Natural Science Foundation of China(NSFC)(No.61635008)This project has also received funding from Enterprise Ireland and the European Union's Horizon 2020 Research and Inno-vation Programme under the Marie Sklodowska-Curie Grant(No.713654)from Science Foundation Ireland and the Sustainable Energy Authority of Ireland(SEAI)under the SFI Career Develop-ment Award Grant(17/CDA/4637).
文摘Atomic force microscopy(AFM)-based electrochemical etching of a highly oriented pyrolytic graphite(HOPG)surface is studied toward the single-atomic-layer lithography of intricate patterns.Electrochemical etching is performed in the water meniscus formed between the AFM tip apex and HOPG surface due to a capillary effect under controlled high relative humid-ity(~75%)at otherwise ambient conditions.The conditions to etch nano-holes,nano-lines,and other intricate patterns are investigated.The clectrochemical reactions of HOPG etching should not generatc debris duc to the conversion of graphite to gaseous CO and CO_(2)based on etching reactions.However,debris is observed on the etched HOPG surface,and incom-plete gasification of carbon occurs during the etching process,resulting in the generation of solid intermediates.Moreover,the applied potential is of critical importance for precise etching,and the precision is also significantly influenced by the AFM tip wear.This study shows that the AFM-based electrochemical etching has the potential to remove the material in a single-atomic-layer precision.This result is likely because the etching process is based on anodic dissolution,resulting in the material removal atom by atom.
基金the Science Foundation Ireland(SFI)(Nos.15/RP/B32O8&SFI/17/CDA/4637)‘111’project by the State Administration of Foreign Experts Affairs and the Ministry of Education of China(No.B07014).
文摘Manufacturing at the atomic scale is the next generation of the industrial revolution.Atomic and close-to-atomic scalemanufacturing(ACSM)helps to achieve this.Atomic force microscopy(AFM)is a promising method for this purposesince an instrument to machine at this small scale has not yet been developed.As the need for increasing the number ofelectronic components inside an integrated circuit chip is emerging in the present-day scenario,methods should be adoptedto reduce the size of connections inside the chip.This can be achieved using molecules.However,connecting moleculeswith the electrodes and then to the external world is challenging.Foundations must be laid to make this possible for thefuture.Atomic layer removal,down to one atom,can be employed for this purpose.Presently,theoretical works are beingperformed extensively to study the interactions happening at the molecule-electrode junction,and how electronic transportis affected by the functionality and robustness of the system.These theoretical studies can be verified experimentally only if nano electrodes are fabricated.Silicon is widely used in the semiconductor industry to fabricate electronic components.Likewise,carbon-based materials such as highly oriented pyrolytic graphite,gold,and silicon carbide find applications inthe electronic device manufacturing sector.Hence,ACSM of these materials should be developed intensively.This paperpresents a review on the state-of-the-art research performed on material removal at the atomic scale by electrochemical andmechanical methods of the mentioned materials using AFM and provides a roadmap to achieve effective mass productionof these devices.
基金UK Research and Innovation,MR/T043172/1Raymond G.P.McQuaid+4 种基金Department for Employment and Learning,Northern Ireland,USI-082Amit KumarEngineering and Physical Sciences Research Council,EP/S037179/1Amit KumarEP/LO15323/01,Nathan Black.
文摘The realization of a mixed-phase microstructure in strained BiFeO_(3)(BFO)thin films has led to numerous novel effects derived from the coexistence of the tetragonal-like monoclinic phase(T phase)and rhombohedral-like monoclinic phase(R phase).Strong strain and polarization diiferences between the phases should result in a high level of transformation plasticity,which enables the continuous alteration of the relative proportion of R and T states in response to external forces.Although the potential for utilizing such plasticity to control mixed-phase populations under external stimuli is evident,direct experi・mental evidence backed by equilibrium predictions has not yet been fully demonstrated.Here we demonstrate deterministic control of mixed-phase populations in an epitaxially strained BFO thin film through the application of localized stresses and electric fields in a reversible manne匚The results illustrate and rationalize deterministic control of mixed phases in strained BFO films,which could be crucial in tuning their functional properties.The findings also highlight a new multiparametric technique in the scanning probe lithography toolbox based on tip-assisted electric and strain field manipulation of functional properties that might find application beyond the ferroelectric domain and structural phase lithography.
文摘Scanning probe microscopy(SPM)and atomic force microscopy(AFM)are widely used for surface imaging and characterization,combining nano-to atomic-scale precision with highly sensitive force measurements.Thus,AFM is considered an enabling technology,impacting many scientific fields,including life and materials sciences.In addition to mapping interaction forces,AFM can be used for the precise application of forces(controlling both location and magnitude),in combination with the application of electrical bias and controlled environments.Moreover,when combined with advances in nanoscale probe technology,SPM-based nanofabrication enables state-of-the-art nanomanufacturing at interfaces.
