Methanol is a safe, economic and easy-to-handle hydrogen source. It has rarely been used in transfer hydrogenation reactions, however. We herein report that a cyclometalated rhodium complex, rhodacycle, catalyzes high...Methanol is a safe, economic and easy-to-handle hydrogen source. It has rarely been used in transfer hydrogenation reactions, however. We herein report that a cyclometalated rhodium complex, rhodacycle, catalyzes highly chemoselective hydrogenation of α,β-unsaturated ketones with methanol as the hydrogen source. A wide variety of chalcones, styryl methyl ketones and vinyl methyl ketones, including sterically demanding ones, were reduced to the saturated ketones in refluxing methanol in a short reaction time, with no need for inter gas protection, and no reduction of the carbonyl moieties was observed. The catalysis described provides a practically easy and operationally safe method for the reduction of olefinic bonds in α,β-unsaturated ketone compounds.展开更多
The finite element method for the conventional theory of mechanism-based strain gradient plasticity is used to study the indentation size effect. For small indenters （e.g., radii on the order of 10μm）, the maximum ...The finite element method for the conventional theory of mechanism-based strain gradient plasticity is used to study the indentation size effect. For small indenters （e.g., radii on the order of 10μm）, the maximum allowable geometrically necessary dislocation （GND） density is introduced to cap the GND density such that the latter does not become unrealistically high. The numerical results agree well with the indentation hardness data of iridium. The GND density is much larger than the density of statistically stored dislocations （SSD） underneath the indenter, but this trend reverses away from the indenter. As the indentation depth （or equivalently, contact radius） increases, the GND density decreases but the SSD density increases.展开更多
Imaging systems in nature have attracted a lot of research interest due to their superior optical and imaging characteristics, Recent advancements in materials science, mechanics, and stretchable electronics have led ...Imaging systems in nature have attracted a lot of research interest due to their superior optical and imaging characteristics, Recent advancements in materials science, mechanics, and stretchable electronics have led to successful development of bioinspired cameras that resemble the structures and functions of biological light-sensing organs. In this review, we discuss some recent progresses in mechanics of bioinspired imaging systems, including tunable hemispherical eyeball camera and artificial compound eye camera. The mechanics models and results reviewed in this article can provide efficient tools for design and optimization of such systems, as well as other related optoelectronic systems that combine rigid elements with soft substrates.展开更多
A new protocol that enables asymmetric hydroaminomethylation of styrenes to afford chiral amines has been developed. Catalysed by an Rh-phosphine species and a chiral phosphoric acid, styrenes are converted into β-ch...A new protocol that enables asymmetric hydroaminomethylation of styrenes to afford chiral amines has been developed. Catalysed by an Rh-phosphine species and a chiral phosphoric acid, styrenes are converted into β-chiral amines with good enantioselectivities under syngas in the presence of an amine and Hantzsch ester. The reaction involves two key steps, hydroformylation and reductive amination, with the former catalysed by the Rh species whilst the latter by the phosphoric acid.展开更多
The buckling of thin gel film has attracted much attention due to its applications in the design of three- dimensional structure from two-dimensional template. We have established an analytical model to study the swel...The buckling of thin gel film has attracted much attention due to its applications in the design of three- dimensional structure from two-dimensional template. We have established an analytical model to study the swelling-induced buckling of a thin gel strip with one edge clamped and the others free. The closed-form solutions for the amplitude and wavelength of the buckled shape are obtained by energy minimization of the total potential energy. The analytical results agree well with finite element analysis based on the inhomogeneous gel theory without any parameter fitting. The model provides a route to study complex postbuckling behaviors of thin gel films and guidelines to design the buckled configuration quantitatively by controlling the swelling ratio.展开更多
Liquid metal(LM)exhibits a distinct combination of high electrical conductivity comparable to that of metals and exceptional deformability derived from its liquid state,thus it is considered a promising material for h...Liquid metal(LM)exhibits a distinct combination of high electrical conductivity comparable to that of metals and exceptional deformability derived from its liquid state,thus it is considered a promising material for high-performance soft electronics.However,rapid patterning LM to achieve a sensory system with high sensitivity remains a challenge,mainly attributed to the poor rheological property and wettability.Here,we report a rheological modification strategy of LM and strain redistribution mechanics to simultaneously simplify the scalable manufacturing process and significantly enhance the sensitivity of LM sensors.By incorporating SiO_(2)particles into LM,the modulus,yield stress,and viscosity of the LM-SiO_(2)composite are drastically enhanced,enabling 3D printability on soft materials for stretchable electronics.The sensors based on printed LM-SiO_(2)composite show excellent mechanical flexibility,robustness,strain,and pressure sensing performances.Such sensors are integrated onto different locations of the human body for wearable applications.Furthermore,by integrating onto a tactile glove,the synergistic effect of strain and pressure sensing can decode the clenching posture and hitting strength in boxing training.When assisted by a deeplearning algorithm,this tactile glove can achieve recognition of the technical execution of boxing punches,such as jab,swing,uppercut,and combination punches,with 90.5%accuracy.This integrated multifunctional sensory system can find wide applications in smart sport-training,intelligent soft robotics,and human-machine interfaces.展开更多
Wearable human-machine interface(HMI)is an advanced technology that has a wide range of applications from robotics to augmented/virtual reality(AR/VR).In this study,an optically driven wearable human-interactive smart...Wearable human-machine interface(HMI)is an advanced technology that has a wide range of applications from robotics to augmented/virtual reality(AR/VR).In this study,an optically driven wearable human-interactive smart textile is proposed by integrating a polydimethylsiloxane(PDMS)patch embedded with optical micro/nanofibers(MNF)array with a piece of textiles.Enabled by the highly sensitive pressure dependent bending loss of MNF,the smart textile shows high sensitivity(65.5 kPa^(−1))and fast response(25 ms)for touch sensing.Benefiting from the warp and weft structure of the textile,the optical smart textile can feel slight finger slip along the MNF.Furthermore,machine learning is utilized to classify the touch manners,achieving a recognition accuracy as high as 98.1%.As a proof-of-concept,a remote-control robotic hand and a smart interactive doll are demonstrated based on the optical smart textile.This optical smart textile represents an ideal HMI for AR/VR and robotics applications.展开更多
The ability to sense heat and touch is essential for healthcare,robotics,and human–machine interfaces.By taking advantage of the engineerable waveguiding properties,we design and fabricate a flexible optical microfib...The ability to sense heat and touch is essential for healthcare,robotics,and human–machine interfaces.By taking advantage of the engineerable waveguiding properties,we design and fabricate a flexible optical microfiber sensor for simultaneous temperature and pressure measurement based on theoretical calculation.The sensor exhibits a high temperature sensitivity of 1.2 nm/℃ by measuring the shift of a high-order mode cutoff wavelength in the short-wavelength range.In the case of pressure sensing,the sensor shows a sensitivity of 4.5%per kilopascal with a fast temporal frequency response of 1000 Hz owing to the strong evanescent wave guided outside the microfiber.The cross talk is negligible because the temperature and pressure signals are measured at different wavelengths based on different mechanisms.The properties of fast temporal response,high temperature,and pressure sensitivity enable the sensor for real-time skin temperature and wrist pulse measurements,which is critical to the accurate analysis of pulse waveforms.We believe the sensor will have great potential in wearable optical devices ranging from healthcare to humanoid robots.展开更多
Cutting-edge technologies of stretchable,skin-mountable,and wearable electronics have attracted tremendous attention recently due to their very wide applications and promising performances.One direction of particular ...Cutting-edge technologies of stretchable,skin-mountable,and wearable electronics have attracted tremendous attention recently due to their very wide applications and promising performances.One direction of particular interest is to investigate novel properties in stretchable electronics by exploring multifunctional materials.Here,we report an integrated strain sensing system that is highly stretchable,rehealable,fully recyclable,and reconfigurable.This system consists of dynamic covalent thermoset polyimine as the moldable substrate and encapsulation,eutectic liquid metal alloy as the strain sensing unit and interconnects,and off-the-shelf chip components for measuring and magnifying functions.The device can be attached on different parts of the human body for accurately monitoring joint motion and respiration.Such a strain sensing system provides a reliable,economical,and ecofriendly solution to wearable technologies,with wide applications in health care,prosthetics,robotics,and biomedical devices.展开更多
With appropriate stimuli,such as heat,humidity,or magnetic field,shape memory polymers(SMPs)can recover to their original shapes from temporary,programmed states.Using thermal responsive SMPs as substrates,we demonstr...With appropriate stimuli,such as heat,humidity,or magnetic field,shape memory polymers(SMPs)can recover to their original shapes from temporary,programmed states.Using thermal responsive SMPs as substrates,we demonstrate a simple method to realize hybrid surface morphologies through confined thin film wrinkling in localized areas.The bilayer system was fabricated by depositing a layer of aluminum thin?lm on top of a SMP substrate programmed with a tensile strain.After the system was heated by a heating wire,hybrid wrinkling patterns were formed in a confined circular area around the heat source,with an inner spoke pattern and an outer ring pattern.Wrinkling patterns showed good symmetry,and the size of the wrinkling area can be tuned by controlling the heat input.This study o?ers a simple but effective approach to fabricate hybrid morphological features in micro-scale.With appropriate stimuli,such as heat,humidity,or magnetic field,shape memory polymers(SMPs)can recover to their original shapes from temporary,programmed states.Using thermal responsive SMPs as substrates,we demonstrate a simple method to realize hybrid surface morphologies through confined thin film wrinkling in localized areas.The bilayer system was fabricated by depositing a layer of aluminum thin?lm on top of a SMP substrate programmed with a tensile strain.After the system was heated by a heating wire,hybrid wrinkling patterns were formed in a confined circular area around the heat source,with an inner spoke pattern and an outer ring pattern.Wrinkling patterns showed good symmetry,and the size of the wrinkling area can be tuned by controlling the heat input.This study offers a simple but effective approach to fabricate hybrid morphological features in micro-scale.展开更多
A chiral cobalt pincer complex,when combined with an achiral electron-rich mono-phosphine ligand,catalyzes efficient asymmetric hydrogenation of a wide range of aryl ketones,affording chiral alcohols with high yields ...A chiral cobalt pincer complex,when combined with an achiral electron-rich mono-phosphine ligand,catalyzes efficient asymmetric hydrogenation of a wide range of aryl ketones,affording chiral alcohols with high yields and moderate to excellent enantioselectivities(29 examples,up to 93%ee).Notably,the achiral mono-phosphine ligand shows a remarkable effect on the enantioselectivity of the reaction.展开更多
基金the Higher Committee for Education Development in Iraq for financial support(AHB)the Commonwealth Scholarships Commission in the UK for a Split-Site PhD Scholarship(RB)
文摘Methanol is a safe, economic and easy-to-handle hydrogen source. It has rarely been used in transfer hydrogenation reactions, however. We herein report that a cyclometalated rhodium complex, rhodacycle, catalyzes highly chemoselective hydrogenation of α,β-unsaturated ketones with methanol as the hydrogen source. A wide variety of chalcones, styryl methyl ketones and vinyl methyl ketones, including sterically demanding ones, were reduced to the saturated ketones in refluxing methanol in a short reaction time, with no need for inter gas protection, and no reduction of the carbonyl moieties was observed. The catalysis described provides a practically easy and operationally safe method for the reduction of olefinic bonds in α,β-unsaturated ketone compounds.
基金Project supported by the National Science Foundation （No. CMS-0084980） ONR （No. N00014-01-1-0205, program officer Dr. Y.D.S. Rajapakse）, by the Foundation for the Author of National Excellent Doctoral Dissertation of China （FANEDD） （No. 2007B30）.
文摘The finite element method for the conventional theory of mechanism-based strain gradient plasticity is used to study the indentation size effect. For small indenters （e.g., radii on the order of 10μm）, the maximum allowable geometrically necessary dislocation （GND） density is introduced to cap the GND density such that the latter does not become unrealistically high. The numerical results agree well with the indentation hardness data of iridium. The GND density is much larger than the density of statistically stored dislocations （SSD） underneath the indenter, but this trend reverses away from the indenter. As the indentation depth （or equivalently, contact radius） increases, the GND density decreases but the SSD density increases.
基金support from ACS Petroleum Research Fund(Grant No.53780-DNI7)NSF(Grant No.CMMI-1405355)
文摘Imaging systems in nature have attracted a lot of research interest due to their superior optical and imaging characteristics, Recent advancements in materials science, mechanics, and stretchable electronics have led to successful development of bioinspired cameras that resemble the structures and functions of biological light-sensing organs. In this review, we discuss some recent progresses in mechanics of bioinspired imaging systems, including tunable hemispherical eyeball camera and artificial compound eye camera. The mechanics models and results reviewed in this article can provide efficient tools for design and optimization of such systems, as well as other related optoelectronic systems that combine rigid elements with soft substrates.
文摘A new protocol that enables asymmetric hydroaminomethylation of styrenes to afford chiral amines has been developed. Catalysed by an Rh-phosphine species and a chiral phosphoric acid, styrenes are converted into β-chiral amines with good enantioselectivities under syngas in the presence of an amine and Hantzsch ester. The reaction involves two key steps, hydroformylation and reductive amination, with the former catalysed by the Rh species whilst the latter by the phosphoric acid.
基金supports from the National Natural Science Foundation of China(Grant Nos.11372272,11622221and 11621062)the National Basic Research Program(Grant No.2015CB351901)the Fundamental Research Funds for the Central Universities
文摘The buckling of thin gel film has attracted much attention due to its applications in the design of three- dimensional structure from two-dimensional template. We have established an analytical model to study the swelling-induced buckling of a thin gel strip with one edge clamped and the others free. The closed-form solutions for the amplitude and wavelength of the buckled shape are obtained by energy minimization of the total potential energy. The analytical results agree well with finite element analysis based on the inhomogeneous gel theory without any parameter fitting. The model provides a route to study complex postbuckling behaviors of thin gel films and guidelines to design the buckled configuration quantitatively by controlling the swelling ratio.
基金J.X.acknowledges financial support from the NSF,USA(CMMI-1762324)Facebook.Y.Q.and H.W.acknowledge financial support from the National Natural Science Foundation of China(Grant no.12202388,11672269,11972323)+2 种基金China Postdoctoral Science Foundation(Grant no.2022M710129,2023T160581)Zhejiang Provincial Natural Science Foundation of China(Grant no.LQ22A020009,LR20A020002)the“Pioneer”and“Leading Goose”R&D Program of Zhejiang(Grant no.2023C01051).
文摘Liquid metal(LM)exhibits a distinct combination of high electrical conductivity comparable to that of metals and exceptional deformability derived from its liquid state,thus it is considered a promising material for high-performance soft electronics.However,rapid patterning LM to achieve a sensory system with high sensitivity remains a challenge,mainly attributed to the poor rheological property and wettability.Here,we report a rheological modification strategy of LM and strain redistribution mechanics to simultaneously simplify the scalable manufacturing process and significantly enhance the sensitivity of LM sensors.By incorporating SiO_(2)particles into LM,the modulus,yield stress,and viscosity of the LM-SiO_(2)composite are drastically enhanced,enabling 3D printability on soft materials for stretchable electronics.The sensors based on printed LM-SiO_(2)composite show excellent mechanical flexibility,robustness,strain,and pressure sensing performances.Such sensors are integrated onto different locations of the human body for wearable applications.Furthermore,by integrating onto a tactile glove,the synergistic effect of strain and pressure sensing can decode the clenching posture and hitting strength in boxing training.When assisted by a deeplearning algorithm,this tactile glove can achieve recognition of the technical execution of boxing punches,such as jab,swing,uppercut,and combination punches,with 90.5%accuracy.This integrated multifunctional sensory system can find wide applications in smart sport-training,intelligent soft robotics,and human-machine interfaces.
基金We acknowledge funding from the National Natural Science Foundation of China(No.61975173)Major Scientific Research Project of Zhejiang Lab(No.2019MC0AD01)+1 种基金Key Research and Development Project of Zhejiang Province(No.2021C05003)the CIE-Tencent Robotics X Rhino-Bird Focused Research Program(No.2020-01-006).
文摘Wearable human-machine interface(HMI)is an advanced technology that has a wide range of applications from robotics to augmented/virtual reality(AR/VR).In this study,an optically driven wearable human-interactive smart textile is proposed by integrating a polydimethylsiloxane(PDMS)patch embedded with optical micro/nanofibers(MNF)array with a piece of textiles.Enabled by the highly sensitive pressure dependent bending loss of MNF,the smart textile shows high sensitivity(65.5 kPa^(−1))and fast response(25 ms)for touch sensing.Benefiting from the warp and weft structure of the textile,the optical smart textile can feel slight finger slip along the MNF.Furthermore,machine learning is utilized to classify the touch manners,achieving a recognition accuracy as high as 98.1%.As a proof-of-concept,a remote-control robotic hand and a smart interactive doll are demonstrated based on the optical smart textile.This optical smart textile represents an ideal HMI for AR/VR and robotics applications.
基金National Key Research and Development Program of China(2018YFB2200400)National Natural Science Foundation of China(61975173,62075192)+2 种基金Natural Science Foundation of Zhejiang Province(LQ21F050001,LQ22F050021)Major Scientific Research Project of Zhejiang Lab(2019MC0AD01)Key Research and Development Project of Zhejiang Province(2021C05003)。
文摘The ability to sense heat and touch is essential for healthcare,robotics,and human–machine interfaces.By taking advantage of the engineerable waveguiding properties,we design and fabricate a flexible optical microfiber sensor for simultaneous temperature and pressure measurement based on theoretical calculation.The sensor exhibits a high temperature sensitivity of 1.2 nm/℃ by measuring the shift of a high-order mode cutoff wavelength in the short-wavelength range.In the case of pressure sensing,the sensor shows a sensitivity of 4.5%per kilopascal with a fast temporal frequency response of 1000 Hz owing to the strong evanescent wave guided outside the microfiber.The cross talk is negligible because the temperature and pressure signals are measured at different wavelengths based on different mechanisms.The properties of fast temporal response,high temperature,and pressure sensitivity enable the sensor for real-time skin temperature and wrist pulse measurements,which is critical to the accurate analysis of pulse waveforms.We believe the sensor will have great potential in wearable optical devices ranging from healthcare to humanoid robots.
基金supported by the National Science Foundation(Grant No.CMMI-1405355)。
文摘Cutting-edge technologies of stretchable,skin-mountable,and wearable electronics have attracted tremendous attention recently due to their very wide applications and promising performances.One direction of particular interest is to investigate novel properties in stretchable electronics by exploring multifunctional materials.Here,we report an integrated strain sensing system that is highly stretchable,rehealable,fully recyclable,and reconfigurable.This system consists of dynamic covalent thermoset polyimine as the moldable substrate and encapsulation,eutectic liquid metal alloy as the strain sensing unit and interconnects,and off-the-shelf chip components for measuring and magnifying functions.The device can be attached on different parts of the human body for accurately monitoring joint motion and respiration.Such a strain sensing system provides a reliable,economical,and ecofriendly solution to wearable technologies,with wide applications in health care,prosthetics,robotics,and biomedical devices.
基金The financial supports from NSF(CMMI-1405355)and ACS Petroleum Research Fund(53780-DNI7)are gratefully acknowledged.
文摘With appropriate stimuli,such as heat,humidity,or magnetic field,shape memory polymers(SMPs)can recover to their original shapes from temporary,programmed states.Using thermal responsive SMPs as substrates,we demonstrate a simple method to realize hybrid surface morphologies through confined thin film wrinkling in localized areas.The bilayer system was fabricated by depositing a layer of aluminum thin?lm on top of a SMP substrate programmed with a tensile strain.After the system was heated by a heating wire,hybrid wrinkling patterns were formed in a confined circular area around the heat source,with an inner spoke pattern and an outer ring pattern.Wrinkling patterns showed good symmetry,and the size of the wrinkling area can be tuned by controlling the heat input.This study o?ers a simple but effective approach to fabricate hybrid morphological features in micro-scale.With appropriate stimuli,such as heat,humidity,or magnetic field,shape memory polymers(SMPs)can recover to their original shapes from temporary,programmed states.Using thermal responsive SMPs as substrates,we demonstrate a simple method to realize hybrid surface morphologies through confined thin film wrinkling in localized areas.The bilayer system was fabricated by depositing a layer of aluminum thin?lm on top of a SMP substrate programmed with a tensile strain.After the system was heated by a heating wire,hybrid wrinkling patterns were formed in a confined circular area around the heat source,with an inner spoke pattern and an outer ring pattern.Wrinkling patterns showed good symmetry,and the size of the wrinkling area can be tuned by controlling the heat input.This study offers a simple but effective approach to fabricate hybrid morphological features in micro-scale.
基金financial support of the National Natural Science Foundation of China(No.21672133)。
文摘A chiral cobalt pincer complex,when combined with an achiral electron-rich mono-phosphine ligand,catalyzes efficient asymmetric hydrogenation of a wide range of aryl ketones,affording chiral alcohols with high yields and moderate to excellent enantioselectivities(29 examples,up to 93%ee).Notably,the achiral mono-phosphine ligand shows a remarkable effect on the enantioselectivity of the reaction.
