We strive to control light

New paper published in Nature Communications! In this paper, we propose a method for dramatically increasing the speed of topographic optical imaging. Instead of the traditional plane by plane interrogation of the surface of interest, our idea is based on performing a binary search. Specifically, we collect a reduced set of images, each integrated during a full focal scan, whilst the illumination is synchronously modulated. The high speed of the technique and its ease of implementation could enable a paradigm shift in optical metrology, allowing the real-time characterization of large or rapidly moving samples. 

New paper published in Nanophotonics! Here, we present a scan-less technology that allows sub-micrometric imaging at thousands of frames per second.We use two acousto-optic deflectors (AODs) placed in a Mach–Zehnder interferometer and drive them simultaneously with multiple acoustic frequencies. As a result, orthogonal light stripes are obtained that interfere at the sample plane, forming a two-dimensional array of flickering spots. The light from the sample is collected with a single photodiode that, after spectrum analysis, allows for image reconstruction at speeds only limited by the AOD’s bandwidth and laser power.

New paper published in Journal of Physics Photonics! In In this review paper, we survey the main applications of acousto optic deflectors (AODs) in neuroscience, from fluorescence imaging to optogenetics. We also review the theory and physical mechanisms of these devices and describe the main configurations developed to accomplish flexible illumination strategies for a better understanding of brain function. 

New paper published in Scientific Reports! In In this article, we show that ultrasound waves featuring a Bessel-like profile can locally modulate the optical properties of a turbid medium to facilitate light guiding. Supported by wave optics and Monte Carlo simulations, we demonstrate how ultrasound enhances light focusing a factor of 7 compared to conventional methods based on placing optical elements outside the complex medium. Combined with point-by-point scanning, images of samples immersed in turbid media with an optical density up to 15, similar to that of weakly scattering biological tissue, can be reconstructed.

New paper published in Ultrasonics! In In this article, we report how combining wavefront sensing and Schlieren tomography enables rapid and direct quantification of 3D pressure fields while obviating any calibration steps. By simultaneously capturing optical phase and intensity information of the US-perturbed fluid using a Wavefront Sensor and Schlieren projections, respectively, 3D pressure fields over several millimeters cubic can be reconstructed after a few seconds. We present a detailed description of the approach and prove its feasibility by characterizing the US field after an acoustic lens, which is in excellent agreement with calibrated hydrophone measurements and simulations.

New paper published in Advanced Materials Technologies! In this article, we present a novel fabrication process compatible with any wet printing method that allows for microlens fabrication with tuned focusing performance. Our approach, called “print-n-release”, is based on modifying the geometry of printed prepolymer microdroplets by using a reconfigurable substrate. Specifically, we used flexible elastomeric materials subject to different types of stress. Upon release, and provided pinning of the contact line, the microdroplets deform because of substrate shrinking. Following a UV-curable step, the microdroplets can then be converted into microlenses whose final shape is no longer dictated exclusively by the wetting behavior between prepolymer and substrate. 

New paper published in Optics and Lasers in Engineering! In this article, we show how the combination of an acousto-optofluidic lens (TAG lens) with pulse illumination enables quantitative phase imaging (QPI) at rates only limited by the camera frame rate. We demonstrate the feasibility  of our approach by measuring different dynamic samples, including an evaporation droplet at rates exceeding 100 phase maps per second. The ease of implementation and tunability of the proposed system opens the door to democratizing QPI in fluid dynamics, histopathology and other fields involving thin transparent samples.

The ICREA Academia program has awarded Dr. Duocastella one of their grants! These awards distinguish the research career of teaching staff working at one of the eight Catalan public universities.

New paper published in Measurement Science and Technology! In this article, in collaboration with the company Sensofar SL, we present an optical system that features a large numerical aperture of 0.3 and a wide field of view (FOV) of 2.9 x 2.9 mm. Such a system is capable of characterizing additively manufactured parts in a single measurement, without the need for lateral stitching to increase the FOV. The proposed system exhibits optical properties that provide facility for large-field, high-resolution measurement of industrially-produced additively manufactured parts.

New paper published in ACS Photonics! In this article, we propose an innovative method for high-speed volumetric light-sheet microscopy. It is based on simultaneously illuminating the sample with a stack of parallel light-sheets created with acousto-optic deflectors. By using an extended depth-of-field detection system, all sample planes appear in focus, and the corresponding information can be acquired in a superimposed single frame. After applying a single-step inversion algorithm, a stack of frames can be decoded into a volumetric image whose signal-to-noise ratio and contrast are greatly enhanced. The method shows promise toward the investigation of fast dynamic sub-cellular processes in thick biological samples.

New paper published in Journal of Colloid and Interface Science in collaboration with the Laboratory of Nanotechnology for precision medicine at IIT. In this article, we show how two-photon polymerization in microfluidic channels is a suitable technique for the continued fabrication of anisotropic micro-particles in the sub-10 µm range. The proposed approach could support the fabrication of micro-hydrogels of well-defined morphology, stiffness, and surface properties for the sustained release of therapeutic agents.

Dr. Duocastella has received an ERC-CoG for his project DEEP!

New paper published in Micromachines. In this article we survey the physics, engineering strategies, and recent implementations of photonic nanojets for high-throughput generation of arbitrary nanopatterns, along with applications in optics, electronics, mechanics, and biosensing. An outlook of the potential impact of nanopatterning technologies based on photonic nanojets in several relevant biomedical areas is also provided.

We are happy to be part of Organvision, a technology proposal to image organoids in real-time and label-free. The project has been funded 3.7 million Euros by Horizon 2020 under the prestigious FET Open RIA program. Organvision comprises of 8 partners spread across 5 cities in 4 countries: Norway (Tromso), Germany (Hamburg, Berlin), Italy (Milan), and Spain (Barcelona).

New paper published in Applied Surface Science. Here, we present a theoretical and experimental study on the effects that film rigidity, elasticity, and plasticity play on laser catapulting. By combining the thermodynamic equations of the laser-generated propulsion force with the theory of thin plate bending, we derived an analytical model that fully describes the list of events responsible for disk ejection. The model is in good agreement with experiments using elastomers, polymers, and metals. A complete printability map based on the film mechanical parameters is reported, which can help to broaden the family of materials suitable for laser additive manufacturing.