Optical Printing of Silicon Nanoparticles as Strain-Driven Nanopixels

Silicon nanoparticles (Si NPs) supporting Mie resonances exhibit vivid structural colors on the subwavelength scale. For future wearable devices, next generation Si-based optical units need to be dynamic and stretchable for display, sensing, or signal processing required by human–computer interaction. Here, by utilizing the distance-sensitive electromagnetic coupling of Mie resonances, we maximize the active tuning effect of Si NP-based structures including dimers, oligomers, and NPs on WS2, which we called Si nanopixels. Through the optical tweezers-assisted printing of Si nanopixels, patterns can be formed on arbitrary flexible substrates. The strain-sensitive tuning of scattering spectra indicates their promising application on strain sensing of various stretchable substrates via a simple “spray and test” process. In the case of Si nanopixels on polydimethylsiloxane (PDMS), local strains around 1% can be detected by a scattering measurement. Moreover, we demonstrate that the scattering intensity variation of Si nanopixels printed on wrinkled tungsten disulfide (WS2) is pixel-dependent and wavelength-dependent. This property facilitates the application of information encryption, and we demonstrate that three barcodes can be independently encoded into the R, G, and B scattering channels through ternary logic represented by the strain-tuning effects of scattering.具备米氏共振（Mie resonances）的硅纳米颗粒（Si NPs）在亚波长尺度下可呈现出鲜明的结构色。面向未来可穿戴设备，下一代硅基光学器件需具备动态可调与可拉伸特性，以满足人机交互所需的显示、传感或信号处理需求。本研究通过利用米氏共振的距离敏感型电磁耦合效应，最大化了基于硅纳米颗粒的结构（包括二聚体、寡聚体以及负载于二硫化钨（WS2）上的纳米颗粒）的主动调控效果，我们将这类结构命名为硅纳米像素（Si nanopixels）。借助光镊辅助打印硅纳米像素的工艺，可在任意柔性衬底上制备目标图案。散射光谱的应变敏感调控特性表明，通过简易的“喷涂-测试”流程，这类结构可应用于各类可拉伸衬底的应变传感。以聚二甲基硅氧烷（PDMS）衬底上的硅纳米像素为例，通过散射测量可检测到约1%的局部应变。此外，本研究证实，印刷于褶皱二硫化钨（WS2）衬底上的硅纳米像素，其散射强度变化具有像素依赖性与波长依赖性。该特性为信息加密应用提供了可能，本研究还展示了通过以散射应变调控效应为表征的三值逻辑，可将三条条形码分别独立编码至红、绿、蓝（R、G、B）散射通道中。