47 research outputs found
Structured Optical Materials Controlled by Light
Materials of which the optical response is determined by their structure are
of much interest both for their fundamental properties and applications.
Examples range from simple gratings to photonic crystals. Obtaining control
over the optical properties is of crucial importance in this context, and it is
often attempted by electro-optical effect or by using magnetic fields. In this
paper, we introduce the use of light to switch and tune the optical response of
a structured material, exploiting a physical deformation induced by light
itself. In this new strategy, light drives an elastic reshaping, which leads to
different spectral properties and hence to a change in the optical response.
This is made possible by the use of liquid crystalline networks structured by
Direct Laser Writing. As a proof of concept, a grating structure with
sub-millisecond time-response is demonstrated for optical beam steering
exploiting an optically induced reversible shape-change. Experimental
observations are combined with finite-element modeling to understand the
actuation process dynamics and to obtain information on how to tune the time
and the power response of this technology. This optical beam steerer serves as
an example for achieving full optical control of light in broad range of
structured optical materials
Photonic Microhand with Autonomous Action
Grabbing and holding objects at the microscale is a complex function, even for microscopic living animals. Inspired by the hominid-type hand, a microscopic equivalent able to catch microelements is engineered. This microhand is light sensitive and can be either remotely controlled by optical illumination or can act autonomously and grab small particles on the basis of their optical properties. Since the energy is delivered optically, without the need for wires or batteries, the artificial hand can be shrunk down to the micrometer scale. Soft material is used, in particular, a custom-made liquid-crystal network that is patterned by a photolithographic technique. The elastic reshaping properties of this material allow finger movement, using environmental light as the only energy source. The hand can be either controlled externally (via the light field), or else the conditions in which it autonomously grabs a particle in its vicinity can be created. This microrobot has the unique feature that it can distinguish between particles of different colors and gray levels. The realization of this autonomous hand constitutes a crucial element in the development of microscopic creatures that can perform tasks without human intervention and self-organized automation at the micrometer scale
Light‐Powered Microrobots: Challenges and Opportunities for Hard and Soft Responsive Microswimmers
Worldwide research in microrobotics has exploded in the past two decades,
leading to the development of microrobots propelled in various manners. Despite
significant advances in the field and successful demonstration of a wide range of
applications, microrobots have yet to become the preferred choice outside a
laboratory environment. After introducing available microrobotic propulsion and
control mechanisms, microrobots that are manufactured and powered by light
are focused herein. Referring to pioneering works and recent interesting
examples, light is presented not only as a fabrication tool, by means of twophoton
polymerization direct laser writing, but also as an actuator for microrobots
in both hard and soft stimuli–responsive polymers. In this scenario, a
number of challenges that yet prevent polymeric light-powered microrobots from
reaching their full potential are identified, whereas potential solutions to overcome
said challenges are suggested. As an outlook, a number of real-world
applications that light-powered microrobots should be particularly suited for are
mentioned, together with the advances needed for them to achieve such purposes.
An interdisciplinary approach combining materials science, microfabrication,
photonics, and data science should be conducive to the next generation of
microrobots and will ultimately foster the translation of microrobotic applications
into the real world
Cellular Contact Guidance on Liquid Crystalline Networks with Anisotropic Roughness
: Cell contact guidance is widely employed to manipulate cell alignment and differentiation in vitro. The use of nano- or micro-patterned substrates allows efficient control of cell organization, thus opening up to biological models that cannot be reproduced spontaneously on standard culture dishes. In this paper, we explore the concept of cell contact guidance by Liquid Crystalline Networks (LCNs) presenting different surface topographies obtained by self-assembly of the monomeric mixture. The materials are prepared by photopolymerization of a low amount of diacrylate monomer dissolved in a liquid crystalline solvent, not participating in the reaction. The alignment of the liquid crystals, obtained before polymerization, determines the scaffold morphology, characterized by a nanometric structure. Such materials are able to drive the organization of different cell lines, e.g., fibroblasts and myoblasts, allowing for the alignment of single cells or high-density cell cultures. These results demonstrate the capabilities of rough surfaces prepared from the spontaneous assembly of liquid crystals to control biological models without the need of lithographic patterning or complex fabrication procedures. Interestingly, during myoblast differentiation, also myotube structuring in linear arrays is observed along the LCN fiber orientation. The implementation of this technology will open up to the formation of muscular tissue with well-aligned fibers in vitro mimicking the structure of native tissues