Light‐Powered Microrobots: Challenges and Opportunities for Hard and Soft Responsive Microswimmers

Bunea, Ada‐Ioana; Martella, Daniele; Nocentini, Sara; Parmeggiani, Camilla; Taboryski, Rafael J.; Wiersma, Diederik S.

doi:10.1002/aisy.202000256

Cited by 79 publications

(59 citation statements)

References 211 publications

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“…The structures were printed using the Nanoscribe Photonic Professional GT+ system (Nanoscribe, Karlsruhe, Germany). This system makes use of the 2PP fabrication technique to reach a lateral resolution < 200 nm and an axial resolution < 700 nm [ 28 ]. The system employs a 780 nm Ti-Sapphire laser with a 150 fs pulse durations at 80 MHz repetition rate [ 26 ], and can print either by scanning the laser over the field of view (FOV) of the objective lens with galvo mirrors or by moving the sample using a piezoelectric stage.…”

Section: Methodsmentioning

confidence: 99%

Bioinspired Microstructured Polymer Surfaces with Antireflective Properties

et al. 2021

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Over the years, different approaches to obtaining antireflective surfaces have been explored, such as using index-matching, interference, or micro- and nanostructures. Structural super black colors are ubiquitous in nature, and biomimicry thus constitutes an interesting way to develop antireflective surfaces. Moth-eye nanostructures, for example, are well known and have been successfully replicated using micro- and nanofabrication. However, other animal species, such as birds of paradise and peacock spiders, have evolved to display larger structures with antireflective features. In peacock spiders, the antireflective properties of their super black patches arise from relatively simple microstructures with lens-like shapes organized in tightly packed hexagonal arrays, which makes them a good candidate for cheap mass replication techniques. In this paper, we present the fabrication and characterization of antireflective microarrays inspired by the peacock spider’s super black structures encountered in nature. Firstly, different microarrays 3D models are generated from a surface equation. Secondly, the arrays are fabricated in a polyacrylate resin by super-resolution 3D printing using two-photon polymerization. Thirdly, the resulting structures are inspected using a scanning electron microscope. Finally, the reflectance and transmittance of the printed structures are characterized at normal incidence with a dedicated optical setup. The bioinspired microlens arrays display excellent antireflective properties, with a measured reflectance as low as 0.042 ± 0.004% for normal incidence, a wavelength of 550 nm, and a collection angle of 14.5°. These values were obtained using a tightly-packed array of slightly pyramidal lenses with a radius of 5 µm and a height of 10 µm.

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Section: Methodsmentioning

confidence: 99%

Bioinspired Microstructured Polymer Surfaces with Antireflective Properties

et al. 2021

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“…Further discussions of the advantages of using light to actuate or manipulate microscale devices can be found in recent reviews. [94,132]…”

Section: Photonics and Plasmonicsmentioning

confidence: 99%

Shape‐Changing Particles: From Materials Design and Mechanisms to Implementation

et al. 2021

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emerging fabrication and synthesis techniques have recently enabled their extension to micro and nanoscale objects. Miniaturization of shape-changing structures allows for their integration into new application areas. As soft actuators are being developed at the micrometer scale, their applications are being realized in biomedical science such as in minimally invasive biopsies, [10,11] targeted drug and cell delivery, [12][13][14] and responsive microfluidics. [15] Since the size of shape-changing structures are approaching the wavelength of visible light, novel approaches to modulate light-matter interactions are being explored with applications in tunable photonics. [16][17][18] Small-scale shapechanging architectures are now being considered as smart building blocks of materials that can be assembled and reconfigured on demand. [19,20] In this review, we discuss mechanisms that facilitate shape changes in micro-and nanostructures as well as their usefulness in several emerging applications. We refer to these structures as "shape-changing particles." We examine a variety of shape-transformations, except the simple case of isotropic volume-change. In Section 2, we review numerous mechanisms that have been recently exploited to change the shape of particles in response to stimuli such as temperature, pH, light, and magnetic fields. We discuss the properties of commonly used materials, including liquid crystal elastomers, [21] responsive hydrogels, [22] and shape-memory polymers [23] as well as techniques for fabricating particles from these materials. We highlight various types of shape transformations such as changing the aspect ratio of microand nanoscale anisotropic particles, [24] bending of microcylinders and particle chains, [25,26] twisting of microribbons, [27] and folding of microscale sheets. [28] Finally, we discuss the challenges and opportunities for programmable shape-morphing and the kinetics of shape change that are controlled by particle size and the mode of stimulation. In Section 3, we review recent applications of shape-changing particles, including photonics, microfluidics, microrobotics, drug delivery, and surgery. In each of these categories, we discuss seminal advances that have been enabled by shape-changing particles, and we discuss their benefits compared to conventional approaches. In Section 4, we identify key unresolved challenges in current applications and areas of research that hold promise for advancing the current state of knowledge of dynamic materials design. Demands for next-generation soft and responsive materials have sparked recent interest in the development of shape-changing particles and particle assemblies. Over the last two decades, a variety of mechanisms that drive shape change have been explored and integrated into particulate systems. Through a combination of top-down fabrication and bottom-up synthesis techniques, shape-morphing capabilities extend from the microscale to the nanoscale. Consequently, shape-morphing particles are rapidly emerging in a variety of co...

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“…corresponding progress has enabled numerous scientific applications in microoptics, [3][4][5][6] mechanics, [7][8][9] biology, [10][11][12] and robotics. [13][14][15][16] However, certain applications require ingredient material properties that polymers just do not provide. For example, the viscoelastic behavior of polymers implies that mechanical resonances with quality factors substantially exceeding ten are not in reach.…”

Section: Doi: 101002/adma202103205mentioning

confidence: 99%