Abstract
New multi-stimuli responsive materials are required in smart systems applications to overcome current limitations in remote actuation and to achieve versatile operation in inaccessible environments. The incorporation of detection mechanisms to quantify in real time the response to external stimuli is crucial for the development of automated systems. Here, we present the first wireless opto-magnetic actuator with mechanochromic response. The device, based on a nanostructured-iron (Fe) layer transferred onto suspended elastomer structures with a periodically corrugated backside, can be actuated both optically (in a broadband spectral range) and magnetically. The combined opto-magnetic stimulus can accurately modulate the mechanical response (strength and direction) of the device. The structural coloration generated at the corrugated back surface enables to easily map and quantify, in 2D, the mechanical deflections by analyzing in real time the hue changes of images taken using a conventional RGB smartphone camera, with a precision of 0.05°. We demonstrate the independent and synergetic optical and magnetic actuation and detection with a detection limit of 1.8 mW·cm–2 and 0.34 mT, respectively. The simple operation, versatility, and cost-effectiveness of the wireless multiactuated device with highly sensitive mechanochromic mapping paves the way to a new generation of wirelessly controlled smart systems.
Highlights
Soft actuators and stimuli-responsive materials are attracting increasing attention in soft robotics, artificial muscles, wearables, and biomimetic devices[1−4] due to their ability to deform and adapt to different environments with high resiliency
The soft opto-magnetic actuator with mechanochromic detection is composed of interconnected semi-shell films comprising magnetic iron (Fe) nanostructures (500 nm) with an average thickness of 80 nm, referred as nanostructured-Fe film, mechanically coupled to a suspended 50 μm thick PDMS film whose back surface is periodically corrugated (Figure 1A)
We have developed a mechanochromic soft Fe/PDMS actuator that is capable of responding to both light and magnetic stimuli, either individually or combined
Summary
Soft actuators and stimuli-responsive materials are attracting increasing attention in soft robotics, artificial muscles, wearables, and biomimetic devices[1−4] due to their ability to deform and adapt to different environments with high resiliency. Current methods to quantify the mechanical response involve either incorporating complex wired electrical contacts and piezoelectric materials,[3,22,28−30] using external bulky laser positioning systems with limited multiplexing capabilities, or analyzing the shape changes via complicated and inefficient imaging analysis, especially for small structures To solve these technological issues, detection based on structural coloration presents several advantages, such as wireless and real-time sensing of the actuation strength.[31,32] the colorimetric detection in wirelessly controlled actuators requires the use of soft materials with sufficient light reflectance or transmittance, and the real-time readout and analysis should be based on image processing rather than on spectrometry to successfully integrate and simplify the detection and to enable fast 2D quantification mapping.[33−35]. This approach would enable the “remote” operation of the system, both actuation and detection, by adjusting the size of the sensor and the optics of the camera to achieve a proper spatial resolution even for long working distances
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