Conformable Holographic Photonic Ink Sensors Based on Adhesive Tapes for Strain Measurements

Mechanically Tunable Flexible Photonic Device for Strain Sensing Applications

Flexible photonic devices based on soft polymers enable real-time sensing of environmental conditions in various industrial applications. A myriad of fabrication techniques have been established for producing optical devices, including photo and electron-beam lithography, nano/femtosecond laser writing, and surface imprinting or embossing. However, among these techniques, surface imprinting/embossing is simple, scalable, convenient to implement, can produce nanoscale resolutions, and is cost-effective. Herein, we utilize the surface imprinting method to replicate rigid micro/nanostructures onto a commonly available PDMS substrate, enabling the transfer of rigid nanostructures into flexible forms for sensing at a nanometric scale. The sensing nanopatterned sheets were mechanically extended, and the extension was remotely monitored via optical methods. Monochromatic light (450, 532, and 650 nm) was transmitted through the imprinted sensor under various force/stress levels. The optical response was recorded on an image screen and correlated with the strain created by the applied stress levels. The optical response was obtained in diffraction pattern form from the flexible grating-based sensor and in an optical-diffusion field form from the diffuser-based sensor. The calculated Young's modulus in response to the applied stress, measured through the novel optical method, was found in a reasonable range compared to the reported range of PDMS (360-870 kPa) in the literature.

Strain -multiplexing optical-tuning based on single-pulsed holographic nanostructures

Holographic flexible and rigid nanostructures in the visible to near infrared range play vital roles in various applications, including displays, data storage, imaging, and security. However, personalized use of holography is limited due to the time-consuming, costly and complex nanofabrication procedures. Personalized holography can be improved/extended through rapid, efficient and low-cost techniques on rigid, flexible and edible materials. Here, we utilize a single-pulsed nanosecond (ns) laser ablation in Denisyuk reflection mode to record one/two-dimension (1/2D) nanostructures on various substrates, including rigid glass coated with soft polymers, gelatin, and conductive (gold) and non-conductive materials (ink) as holographic multilayer metastructures (HMMs). The tunability of optical properties was investigated by illuminating monochromatic and broadband light sources on flexible-template nanostructures. The surface morphologies of the nano-structures were changed by applying mechanical force, which in turn tuned the far-field optical response depending upon the amount of applied force, acting as an optical shape and force sensor. Nanostructures engineered on an edible material (gelatin) as well as on soft polymers (polymeric diffusers) were also demonstrated for suitable application in food industries and optoelectronics.