ecent Advances in the Science of Burst Wave Lithotripsy and Ultrasonic Propulsion

Objective.Retinal degeneration involving progressive deterioration and loss of function of photoreceptors is a major cause of permanent vision loss worldwide.Strategies to treat these incurable conditions incorporate retinal prostheses via electrically stimulating surviving retinal neurons with implanted devices in the eye,optogenetic therapy,and sonogenetic therapy.Existing challenges of these strategies include invasive manner,complex implantation surgeries,and risky gene therapy.Methods and Results.Here,we show that direct ultrasound stimulation on the retina can evoke neuron activities from the visual centers including the superior colliculus and the primary visual cortex(V1),in either normal-sighted or retinal degenerated blind rats in vivo.The neuron activities induced by the customized spherically focused 3.1 MHz ultrasound transducer have shown both good spatial resolution of 250μm and temporal resolution of 5 Hz in the rat visual centers.An additional customized 4.4 MHz helical transducer was further implemented to generate a static stimulation pattern of letter forms.Conclusion.Our findings demonstrate that ultrasound stimulation of the retina in vivo is a safe and effective approach with high spatiotemporal resolution,indicating a promising future of ultrasound stimulation as a novel and noninvasive visual prosthesis for translational applications in blind patients.

3D Printing of Nacre-Inspired Structures with Exceptional Mechanical and Flame-Retardant Properties

Flame-retardant and thermal management structures have attracted great attention duc to the requirement of high-temperature exposure in industrial,aerospace,and thermal power fields,but the development of protoctive fire-retardant structures with complex shapes to fit arbitrary surfaces is still challenging.Herein,we reported a rotation-blade casting-assisted 3D printing process to fabricate nacre-inspired structures with exceptional mechanical and flame-retardant properties,and the relatedi fundamental mechanisms are studied.3-(Trimethoxysilyl)propyl methacrylate(TMSPMA)modified boron nitride nanoplatelets(BNs)were aligned by rotation-blade casting during the 3D printing process to build the"hrick and mortar"architecture.The 3D printed structures are more lightweight,while having higher fracture toughness than the natural nacre,which is attributed to the crack deflection,aligned BN(a-BNs)bridging,and pull-outs reinforced structures by the covalent bonding between TMSPMA grafted a-BNs and polymer matrix.Thermal conductivity is enhanced by 25.5 times compared with pure polymer and 5.8 times of anisotropy due to the interconnection of a-BNs.3D printed heat-exchange structures with vertically aligned BNs in complex shapes were demonstrated for efficient thermal control of high-power light-emitting diocles.3D printed helmet and armor with a-BNs show exceptional mechanical and fire-retardant properties,demonstrating integrated mechanical and thermal protection.