It is well-recognized that the electromechanical response of a nanostructure is affected by its element size. In the present article, the size dependent stability behavior and nanotweezers fabricated from nanowires ar...It is well-recognized that the electromechanical response of a nanostructure is affected by its element size. In the present article, the size dependent stability behavior and nanotweezers fabricated from nanowires are investigated by modified couple stress elasticity （MCSE）. The governing equation of the nanotweezers is obtained by taking into account the presence of Coulomb and intermolecular attractions. To solve the equation, four techniques, i.e., the modified variational iteration method （MVIM）, the monotonic iteration method （MIM）, the MAPLE numerical solver, and a lumped model, are used. The variations of the arm displacement of the tweezers versus direct current （DC） voltage are obtained. The instability parameters, i.e., pull-in voltage and deflection of the system, are computed. The results show that size-dependency will affect the stability of the nanotweezers significantly if the diameter of the nanowire is of the order of the length scale. The impact of intermolecular attraction on the size-dependent stability of the system is discussed.展开更多
Diameter- and chirality-dependent interactions between aromatic molecule-based nanotweezers and single-walled carbon nanotubes (SWNTs) are revealed by density functional theory calculations. We found that the threshol...Diameter- and chirality-dependent interactions between aromatic molecule-based nanotweezers and single-walled carbon nanotubes (SWNTs) are revealed by density functional theory calculations. We found that the threshold diameter of selected SWNTs is determined by the end-to-end distance of the nanotweezer. Large-diameter SWNTs are preferred by a nanotweezer with an obtuse folding angle, whereas small-diameter SWNTs are favored by a nanotweezer with an acute folding angle. The adsorption can be further stabilized by the orientational alignment of the hexagonal rings of the nanotweezer and the SWNT sidewall. Therefore, by taking advantage of the supramolecular recognition ability of the aromatic molecule-based nanotweezer, SWNTs can be enriched with both controllable diameter and chirality.展开更多
Surface plasmonic resonance(SPR)has been a corner stone for approaching single molecular detection due to its highsensitivity capability and simple detection mechanism,and has brought major advancements in biomedicine...Surface plasmonic resonance(SPR)has been a corner stone for approaching single molecular detection due to its highsensitivity capability and simple detection mechanism,and has brought major advancements in biomedicine and life science technology.Over decades,the successful integration of SPR with versatile techniques has been demonstrated.However,several crucial limitations have hindered this technique for practical applications,such as long detection time and low overall sensitivity.This review aims to provide a comprehensive summary of existing approaches in enhancing the performance of SPR sensors based on“passive”and“active”methods.Firstly,passive enhancement is discussed from a material aspect,including signal amplification tags and modifications of conventional substrates.Then,the focus is on the most popular active enhancement methods including electrokinetic,optical,magnetic,and acoustic manipulations that are summarized with highlights on their advantageous features and ability to concentrate target molecules at the detection sites.Lastly,prospects and future development directions for developing SPR sensing towards a more practical,single molecular detection technique in the next generation are discussed.This review hopes to inspire researchers’interests in developing SPR-related technology with more innovative and influential ideas.展开更多
The killing of tumor cells by ionizing radiation beams in cancer radiotherapy is currently based on a rather empirical understanding of the basic mechanisms and effectiveness of DNA damage by radiation.By contrast,the...The killing of tumor cells by ionizing radiation beams in cancer radiotherapy is currently based on a rather empirical understanding of the basic mechanisms and effectiveness of DNA damage by radiation.By contrast,the mechanical behaviour of DNA encompassing sequence sensitivity and elastic transitions to plastic responses is much better understood.A novel approach is proposed here based on a micromechanical Silicon Nanotweezers device.This instrument allows the detailed biomechanical characterization of a DNA bundle exposed to an ionizing radiation beam delivered here by a therapeutic linear particle accelerator(LINAC).The micromechanical device endures the harsh environment of radiation beams and still retains molecular-level detection accuracy.In this study,the first real-time observation of DNA damage by ionizing radiation is demonstrated.The DNA bundle degradation is detected by the micromechanical device as a reduction of the bundle stiffness,and a theoretical model provides an interpretation of the results.These first real-time observations pave the way for both fundamental and clinical studies of DNA degradation mechanisms under ionizing radiation for improved tumor treatment.展开更多
The precise control and manipulation of micro-and nanoparticles using an optical endoscope are potentially important in biomedical studies,bedside diagnosis and treatment in an aquatic internal organ environment,but t...The precise control and manipulation of micro-and nanoparticles using an optical endoscope are potentially important in biomedical studies,bedside diagnosis and treatment in an aquatic internal organ environment,but they have not yet been achieved.Here,for the first time,we demonstrate optical nonlinear endoscopic tweezers(ONETs)for directly controlling and manipulating aquatic micro-and nanobeads as well as gold nanorods.It is found that two-photon absorption can enhance the trapping force on fluorescent nanobeads by up to four orders of magnitude compared with dielectric nanobeads of the same size.More importantly,two-photon excitation leads to a plasmon-mediated optothermal attracting force on nanorods,which can extend far beyond the focal spot.This new phenomenon facilitates a snowball effect that allows the fast uploading of nanorods to a targeted cell followed by thermal treatment within 1 min.As two-photon absorption allows an operation wavelength at the center of the transmission window of human tissue,our work demonstrates that ONET is potentially an unprecedented tool for precisely specifying the location and dosage of drug particles and for rapidly uploading metallic nanoparticles to individual cancer cells for treatment.展开更多
文摘It is well-recognized that the electromechanical response of a nanostructure is affected by its element size. In the present article, the size dependent stability behavior and nanotweezers fabricated from nanowires are investigated by modified couple stress elasticity （MCSE）. The governing equation of the nanotweezers is obtained by taking into account the presence of Coulomb and intermolecular attractions. To solve the equation, four techniques, i.e., the modified variational iteration method （MVIM）, the monotonic iteration method （MIM）, the MAPLE numerical solver, and a lumped model, are used. The variations of the arm displacement of the tweezers versus direct current （DC） voltage are obtained. The instability parameters, i.e., pull-in voltage and deflection of the system, are computed. The results show that size-dependency will affect the stability of the nanotweezers significantly if the diameter of the nanowire is of the order of the length scale. The impact of intermolecular attraction on the size-dependent stability of the system is discussed.
基金This work was supported by the the National Natural Science Foundation of China(NSFC)(Nos.10774003,10474123,10434010,90626223,and 20731162012)the National Basic Research Program of China(973 Program)(Nos.2002CB613505 and 2007CB936200,MOST of China)+2 种基金the Program for New Century Excellent Talents in University of Ministry of Education of China,National Foundation for Fostering Talents of Basic Science(No.J0630311)and Nebraska Research Initiative of USA(No.4132050400)We thank R.M.Tromp and A.Afzali for helpful discussions of solvent effects.
文摘Diameter- and chirality-dependent interactions between aromatic molecule-based nanotweezers and single-walled carbon nanotubes (SWNTs) are revealed by density functional theory calculations. We found that the threshold diameter of selected SWNTs is determined by the end-to-end distance of the nanotweezer. Large-diameter SWNTs are preferred by a nanotweezer with an obtuse folding angle, whereas small-diameter SWNTs are favored by a nanotweezer with an acute folding angle. The adsorption can be further stabilized by the orientational alignment of the hexagonal rings of the nanotweezer and the SWNT sidewall. Therefore, by taking advantage of the supramolecular recognition ability of the aromatic molecule-based nanotweezer, SWNTs can be enriched with both controllable diameter and chirality.
基金the National Natural Science Foundation of China(No.61905145)Guangdong Natural Science Foundation and Province Project(No.2021A1515011916)Shenzhen Science and Technology R&D and Innovation Foundation(No.JCYJ20200109105608771).
文摘Surface plasmonic resonance(SPR)has been a corner stone for approaching single molecular detection due to its highsensitivity capability and simple detection mechanism,and has brought major advancements in biomedicine and life science technology.Over decades,the successful integration of SPR with versatile techniques has been demonstrated.However,several crucial limitations have hindered this technique for practical applications,such as long detection time and low overall sensitivity.This review aims to provide a comprehensive summary of existing approaches in enhancing the performance of SPR sensors based on“passive”and“active”methods.Firstly,passive enhancement is discussed from a material aspect,including signal amplification tags and modifications of conventional substrates.Then,the focus is on the most popular active enhancement methods including electrokinetic,optical,magnetic,and acoustic manipulations that are summarized with highlights on their advantageous features and ability to concentrate target molecules at the detection sites.Lastly,prospects and future development directions for developing SPR sensing towards a more practical,single molecular detection technique in the next generation are discussed.This review hopes to inspire researchers’interests in developing SPR-related technology with more innovative and influential ideas.
基金G.P.received a Doctoral Scholarship from the Institut National du Cancer and additional financial support provided by CNRS.
文摘The killing of tumor cells by ionizing radiation beams in cancer radiotherapy is currently based on a rather empirical understanding of the basic mechanisms and effectiveness of DNA damage by radiation.By contrast,the mechanical behaviour of DNA encompassing sequence sensitivity and elastic transitions to plastic responses is much better understood.A novel approach is proposed here based on a micromechanical Silicon Nanotweezers device.This instrument allows the detailed biomechanical characterization of a DNA bundle exposed to an ionizing radiation beam delivered here by a therapeutic linear particle accelerator(LINAC).The micromechanical device endures the harsh environment of radiation beams and still retains molecular-level detection accuracy.In this study,the first real-time observation of DNA damage by ionizing radiation is demonstrated.The DNA bundle degradation is detected by the micromechanical device as a reduction of the bundle stiffness,and a theoretical model provides an interpretation of the results.These first real-time observations pave the way for both fundamental and clinical studies of DNA degradation mechanisms under ionizing radiation for improved tumor treatment.
文摘The precise control and manipulation of micro-and nanoparticles using an optical endoscope are potentially important in biomedical studies,bedside diagnosis and treatment in an aquatic internal organ environment,but they have not yet been achieved.Here,for the first time,we demonstrate optical nonlinear endoscopic tweezers(ONETs)for directly controlling and manipulating aquatic micro-and nanobeads as well as gold nanorods.It is found that two-photon absorption can enhance the trapping force on fluorescent nanobeads by up to four orders of magnitude compared with dielectric nanobeads of the same size.More importantly,two-photon excitation leads to a plasmon-mediated optothermal attracting force on nanorods,which can extend far beyond the focal spot.This new phenomenon facilitates a snowball effect that allows the fast uploading of nanorods to a targeted cell followed by thermal treatment within 1 min.As two-photon absorption allows an operation wavelength at the center of the transmission window of human tissue,our work demonstrates that ONET is potentially an unprecedented tool for precisely specifying the location and dosage of drug particles and for rapidly uploading metallic nanoparticles to individual cancer cells for treatment.
