More Like this

1. Additive Opto-Thermomechanical Nanoprinting and Nanorepairing under Ambient Conditions

   https://doi.org/10.1021/acs.nanolett.0c01261  

   Alam, Md Shah; Zhan, Qiwen; Zhao, Chenglong (June 2020, Nano Letters)

   We demonstrate an opto-thermomechanical (OTM) nanoprinting method that allows us not only to additively print nanostructures with sub-100 nm accuracy but also to correct printing errors for nanorepairing under ambient conditions. Different from other existing nanoprinting methods, this method works when a nanoparticle on the surface of a soft substrate is illuminated by a continuous-wave (cw) laser beam in a gaseous environment. The laser heats the nanoparticle and induces a rapid thermal expansion of the soft substrate. This thermal expansion can either release a nanoparticle from the soft surface for nanorepairing or transfer it additively to another surface in the presence of optical forces for nanoprinting with sub-100 nm accuracy. Details of the printing mechanism and parameters that affect the printing accuracy are investigated. This additive OTM nanoprinting technique paves the way for rapid and affordable additive manufacturing or 3D printing at the nanoscale under ambient conditions. 

   more » « less
2. Design of Bistable Soft Deployable Structures via a Kirigami‐Inspired Planar Fabrication Approach

   https://doi.org/10.1002/admt.202300088  

   Mungekar, Mrunmayi; Ma, Leixin; Yan, Wenzhong; Kackar, Vishal; Shokrzadeh, Shyan; Jawed, Mohammad_Khalid (May 2023, Advanced Materials Technologies)

   Abstract Fully soft bistable mechanisms have shown extensive applications ranging from soft robotics, wearable devices, and medical tools, to energy harvesting. However, the lack of design and fabrication methods that are easy and potentially scalable limits their further adoption into mainstream applications. Herein, a top–down planar approach is presented by introducing Kirigami‐inspired engineering combined with a pre‐stretching process. Using this method, Kirigami‐Pre‐stretched Substrate‐Kirigami trilayered precursors are created in a planar manner; upon release, the strain mismatch—due to the pre‐stretching of substrate—between layers will induce an out‐of‐plane buckling to achieve targeted 3D bistable structures. By combining experimental characterization, analytical modeling, and finite element simulation, the effect of the pattern size of Kirigami layers and pre‐stretching on the geometry and stability of resulting 3D composites is explored. In addition, methods to realize soft bistable structures with arbitrary shapes and soft composites with multistable configurations are investigated, which may encourage further applications. This method is demonstrated by using bistable soft Kirigami composites to construct two soft machines: (i) a bistable soft gripper that can gently grasp delicate objects with different shapes and sizes and (ii) a flytrap‐inspired robot that can autonomously detect and capture objects. 

   more » « less
3. Evidence of non-isentropic release from high residual temperatures in shocked metals measured with ultrafast x-ray diffraction

   https://doi.org/10.1063/5.0217779  

   Yang, Hong; Armstrong, Michael_R; Austin, Ryan_A; Radousky, Harry_B; Patel, Akshat_Hetal; Wei, Tiwei; Goncharov, Alexander_F; Mao, Wendy_L; Granados, Eduardo; Lee, Hae_Ja; et al (August 2024, Journal of Applied Physics)

   Shock experiments are widely used to understand the mechanical and electronic properties of matter under extreme conditions. However, after shock loading to a Hugoniot state, a clear description of the post-shock thermal state and its impacts on materials is still lacking. We used diffraction patterns from 100-fs x-ray pulses to investigate the temperature evolution of laser-shocked Al–Zr metal film composites at time delays ranging from 5 to 75 ns driven by a 120-ps short-pulse laser. We found significant heating of both Al and Zr after shock release, which can be attributed to heat generated by inelastic deformation. A conventional hydrodynamic model that employs (i) typical descriptions of Al and Zr mechanical strength and (ii) elevated strength responses (which might be attributed to an unknown strain rate dependence) did not fully account for the measured temperature increase, which suggests that other strength-related mechanisms (such as fine-scale void growth) could play an important role in thermal responses under shock wave loading/unloading cycles. Our results suggest that a significant portion of the total shock energy delivered by lasers becomes heat due to defect-facilitated plastic work, leaving less converted to kinetic energy. This heating effect may be common in laser-shocked experiments but has not been well acknowledged. High post-shock temperatures may induce phase transformation of materials during shock release. Another implication for the study is the preservability of magnetic records from planetary surfaces that have a shock history from frequent impact events. 

   more » « less
4. Voltage modulated magnetic anisotropy of rare earth iron garnet thin films on a piezoelectric substrate

   https://doi.org/10.1063/5.0128842  

   Gross, Miela J.; Misba, Walid A.; Hayashi, Kensuke; Bhattacharya, Dhritiman; Gopman, Daniel B.; Atulasimha, Jayasimha; Ross, Caroline A. (December 2022, Applied Physics Letters)

   Voltage-tuning of magnetic anisotropy is demonstrated in ferrimagnetic insulating rare earth iron garnets on a piezoelectric substrate, (011)-oriented PMN-PT. A 42 nm thick yttrium-substituted dysprosium iron garnet (YDyIG) film is grown via pulsed laser deposition followed by a rapid thermal anneal to crystallize the garnet into ≈5  μm diameter grains. The annealed polycrystalline film is magnetically isotropic in the film plane with total anisotropy dominated by shape and magnetoelastic contributions. Application of an electric field perpendicular to the substrate breaks the in-plane easy axis along [01[Formula: see text]] and an intermediate axis along [100]. The results are explained in terms of the piezoelectric remanent strain caused by poling the substrate, which is transferred to the YDyIG and modulates the magnetoelastic anisotropy. 

   more » « less
5. Fabrication of hierarchical sapphire nanostructures using ultrafast laser induced morphology change

   https://doi.org/10.1088/1361-6528/adab7c  

   Cheung, Joshua; Chien, Kun-Chieh; Sokalski, Peter; Shi, Li; Chang, Chih-Hao (January 2025, Nanotechnology)

   Abstract Sapphire is an attractive material that stands to benefit from surface functionalization effects stemming from micro/nanostructures. Here we investigate the use of ultrafast lasers for fabricating sapphire nanostructures by exploring the relationship between irradiation parameters, morphology change, and selective etching. In this approach a femtosecond laser pulse is focused on the substrate to change the crystalline morphology to amorphous or polycrystalline, which is characterized by examining different vibrational modes using Raman spectroscopy. The irradiated regions are removed using a subsequent hydrofluoric acid etch. Laser confocal measurements quantify the degree of selective etching. The results indicate a threshold laser pulse intensity required for selective etching. This process was used to fabricate hierarchical sapphire nanostructures over large areas with enhanced hydrophobicity, with an apparent contact angle of 140 degrees, and a high roll-off angle, characteristic of the rose petal effect. Additionally, the structures have high broadband diffuse transmittance of up to 81.8% with low loss, with applications in optical diffusers. Our findings provide new insights into the interplay between the light-matter interactions, where Raman shifts associated with different vibrational modes can predict selective etching. These results advance sapphire nanostructure fabrication, with applications in infrared optics, protective windows, and consumer electronics. 

   more » « less