With the advent of 5G and future trends for communication systems moving to millimeter wave(MMW)and higher frequencies,antennas will be required to have high gain,wide bandwidth,and low losses.3D printing realizes str...With the advent of 5G and future trends for communication systems moving to millimeter wave(MMW)and higher frequencies,antennas will be required to have high gain,wide bandwidth,and low losses.3D printing realizes structures by sequential stacking layer-by-layer,which enables the manufacturing of antennas with ar-bitrary shapes in a cheaper,faster,and flexible manner.This study provides a review of current state-of-the-art 3D printed antennas for different frequencies.First,an overview of 3D printing technology is presented.A huge number of 3D printed antennas,categorized by their material composition,have been described,including poly-mer,metallic,ceramic,composite material,and multi-material integrated antennas.Finally,the main challenges and prospects are discussed to provide insight into how 3D printing can be further progressed in antenna manu-facturing.展开更多
The achromatic subdiffraction lens with large numerical aperture(NA)is of significant importance in optical imaging,photolithography,spectroscopy,and nanophotonics.However,most of the previous research on sub-diffract...The achromatic subdiffraction lens with large numerical aperture(NA)is of significant importance in optical imaging,photolithography,spectroscopy,and nanophotonics.However,most of the previous research on sub-diffraction lenses has been restricted by limited bandwidth and efficiency as well as severe chromatic aberrations.In this paper,a semicircular gradient index lens(sGRIN)with a modified refractive index profile originated from a Maxwell fish-eye lens is put forward to achieve highly efficient(above 81%)achromatic(4–20 GHz)subdiffraction focusing at the focusing line(around 0.28λ)with large NA of 1.3 and broadband diffraction-limited far-field radiation(4–16 GHz)theoretically,which overcomes the drawbacks of previous works.The presented lens is designed by gradient dielectric metamaterials.Evanescent waves ignited at the lens/air interface and transformation of electromagnetic(EM)waves with high spatial frequency in sGRIN to EM waves with low spatial frequency in air are responsible for subdiffraction focusing and diffraction-limited far-field radiation,respectively.Experimental results demonstrate the excellent performance of achromatic subdiffraction focusing and diffraction-limited far-field radiation.The presented lens has great potential to be applied in subdiffraction imaging systems.展开更多
Understanding working principles and thermodynamics behind phase separations,which have significant influences on condensed molecular structures and their performances,can inspire to design and fabricate anomalously a...Understanding working principles and thermodynamics behind phase separations,which have significant influences on condensed molecular structures and their performances,can inspire to design and fabricate anomalously and desirably mechanoresponsive hydrogels.However,a combination of techniques from physicochemistry and mechanics has yet been established for the phase separation in hydrogels.In this study,a thermodynamic model is firstly formulated to describe solvent-aided phase and microphase separations in the hydrogels,which present significantly improved mechanoresponsive strengths.Flory-Huggins theory and interfacial energy equation have further been applied to model the thermodynamics of concentration-dependent and temperature-dependent phase separations.An intricately detailed phase map has finally been formulated to explore the working principle.The thermodynamic methodology of phase separations,combined with the constitutive stress-strain relationships,has a great potential to explore the working mechanisms in mechanoresponsive hydrogels.展开更多
基金supported by National Natural Science Foundation of China(Grant.No.52275310).
文摘With the advent of 5G and future trends for communication systems moving to millimeter wave(MMW)and higher frequencies,antennas will be required to have high gain,wide bandwidth,and low losses.3D printing realizes structures by sequential stacking layer-by-layer,which enables the manufacturing of antennas with ar-bitrary shapes in a cheaper,faster,and flexible manner.This study provides a review of current state-of-the-art 3D printed antennas for different frequencies.First,an overview of 3D printing technology is presented.A huge number of 3D printed antennas,categorized by their material composition,have been described,including poly-mer,metallic,ceramic,composite material,and multi-material integrated antennas.Finally,the main challenges and prospects are discussed to provide insight into how 3D printing can be further progressed in antenna manu-facturing.
基金National Key Research and Development Program of China(2017YPA0303702)National Natural Science Foundation of China(11634005,11872113,11974176,61671314).
文摘The achromatic subdiffraction lens with large numerical aperture(NA)is of significant importance in optical imaging,photolithography,spectroscopy,and nanophotonics.However,most of the previous research on sub-diffraction lenses has been restricted by limited bandwidth and efficiency as well as severe chromatic aberrations.In this paper,a semicircular gradient index lens(sGRIN)with a modified refractive index profile originated from a Maxwell fish-eye lens is put forward to achieve highly efficient(above 81%)achromatic(4–20 GHz)subdiffraction focusing at the focusing line(around 0.28λ)with large NA of 1.3 and broadband diffraction-limited far-field radiation(4–16 GHz)theoretically,which overcomes the drawbacks of previous works.The presented lens is designed by gradient dielectric metamaterials.Evanescent waves ignited at the lens/air interface and transformation of electromagnetic(EM)waves with high spatial frequency in sGRIN to EM waves with low spatial frequency in air are responsible for subdiffraction focusing and diffraction-limited far-field radiation,respectively.Experimental results demonstrate the excellent performance of achromatic subdiffraction focusing and diffraction-limited far-field radiation.The presented lens has great potential to be applied in subdiffraction imaging systems.
基金financially supported by the National Natural Science Foundation of China NSFC(Grant 11725208)Newton Mobility(Grant IE161019)through Royal SocietyNSFC.
文摘Understanding working principles and thermodynamics behind phase separations,which have significant influences on condensed molecular structures and their performances,can inspire to design and fabricate anomalously and desirably mechanoresponsive hydrogels.However,a combination of techniques from physicochemistry and mechanics has yet been established for the phase separation in hydrogels.In this study,a thermodynamic model is firstly formulated to describe solvent-aided phase and microphase separations in the hydrogels,which present significantly improved mechanoresponsive strengths.Flory-Huggins theory and interfacial energy equation have further been applied to model the thermodynamics of concentration-dependent and temperature-dependent phase separations.An intricately detailed phase map has finally been formulated to explore the working principle.The thermodynamic methodology of phase separations,combined with the constitutive stress-strain relationships,has a great potential to explore the working mechanisms in mechanoresponsive hydrogels.
