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Scientific Highlights

This section includes a list of the highlighted IMB-CNM scientific papers published in journals included in the Science Citation Index (SCI), per year of publication.

FDTD simulations of the near-field interaction between two identical nearly touching plasmonic NPs. Adv. Fun. Mat.
Soft Optomechanical Systems for Sensing, Modulation, and Actuation
Ferran Pujol-Vila, Pau Güell-Grau, Josep Nogués, Mar Alvarez, Borja Sepúlveda

Soft optomechanical systems have the ability to reversibly respond to optical and mechanical external stimuli by changing their own properties (e.g., shape, size, viscosity, stiffness, color or transmittance). These systems typically combine the optical properties of plasmonic, dielectric or carbon-based nanomaterials with the high elasticity and deformability of soft polymers, thus opening the path for the development of new mechanically tunable optical systems, sensors, and actuators for a wide range of applications. This review focuses on the recent progresses in soft optomechanical systems, which are here classified according to their applications and mechanisms of optomechanical response. The first part summarizes the soft optomechanical systems for mechanical sensing and optical modulation based on the variation of their optical response under external mechanical stimuli, thereby inducing mechanochromic or intensity modulation effects. The second part describes the soft optomechanical systems for the development of light induced mechanical actuators based on different actuation mechanisms, such as photothermal effects and phase transitions, among others. The final section provides a critical analysis of the main limitations of current soft optomechanical systems and the progress that is required for future devices.

Adv. Funct. Mater. 2023, DOI: 10.1002/adfm.202213109

Confocal microscopy image of the wrinkled PDMS surface. Adv. Mat.
Elastic Plasmonic-Enhanced Fabry–Pérot Cavities with Ultrasensitive Stretching Tunability
Pau Güell-Grau, Francesc Pi, Rosa Villa, Olof Eskilson, Daniel Aili, Josep Nogués, Borja Sepúlveda, Mar Alvarez

The emerging stretchable photonics field faces challenges, like the robust integration of optical elements into elastic matrices or the generation of large optomechanical effects. Here, the first stretchable plasmonic-enhanced and wrinkled Fabry–Pérot (FP) cavities are demonstrated, which are composed of self-embedded arrays of Au nanostructures at controlled depths into elastomer films. The novel self-embedding process is triggered by the Au nanostructures’ catalytic activity, which locally increases the polymer curing rate, thereby inducing a mechanical stress that simultaneously pulls the Au nanostructures into the polymer and forms a wrinkled skin layer. This geometry yields unprecedented optomechanical effects produced by the coupling of the broad plasmonic modes of the Au nanostructures and the FP modes, which are modulated by the wrinkled optical cavity. As a result, film stretching induces drastic changes in both the spectral position and intensity of the plasmonic-enhanced FP resonances due to the simultaneous cavity thickness reduction and cavity wrinkle flattening, thus increasing the cavity finesse. These optomechanical effects are exploited to demonstrate new strain-sensing approaches, achieving a strain detection limit of 0.006%, i.e., 16-fold lower than current optical strain-detection schemes.

Adv. Mater. 2022, 34, 2106731. DOI: 10.1002/adma.202106731

Cartoon of microrobots at cell scale for biomedical applications
Robotic probes at the cell scale
José A. Plaza

The miniaturization of robotic tools and probes enables the fundamental study of mechanical properties of cells and tissues.

Science Robotics, 25 Jan 2023, Vol 8, Issue 74, DOI: 10.1126/scirobotics.adf9996

El tallo verde es una estructura compostable y en las hojas de la flor se produce la evaporación. Crédito: Carles Tortosa
A plant-like battery: a biodegradable power source ecodesigned for precision agriculture
Marina Navarro-Segarra, Carles Tortosa, Carlos Ruiz-Díez, Denis Desmaële, Teresa Gea, Raquel Barrena, Neus Sabaté and Juan Pablo Esquivel

The natural environment has always been a source of inspiration for the research community. Nature has evolved over thousands of years to create the most complex living systems, with the ability to leverage inner and outside energetic interactions in the most efficient way. This work presents a flow battery profoundly inspired by nature, which mimics the fluid transport in plants to generate electric power. The battery was ecodesigned to meet a life cycle for precision agriculture (PA) applications; from raw material selection to disposability considerations, the battery is conceived to minimize its environmental impact while meeting PA power requirements.

Energy & Environmental Science, 2022, Issue 7, DOI:10.1039/D2EE00597B

Ejercito de chips de silicio en forma de estrella sobre una población de células HeLa | CSIC.
Intracellular Mechanical Drugs Induce Cell-Cycle Altering and Cell Death
Arjona, M. I., Duch, M., Hernández-Pinto, A., Vázquez, P., Agusil, J. P., Gómez-Martínez, R., Redondo-Horcajo, M., Amirthalingam, E., Pérez-García, L., Suárez, T., Plaza, J. A.

Current advances in materials science have demonstrated that extracellular mechanical cues can define cell function and cell fate. However, a fundamental understanding of the manner in which intracellular mechanical cues affect cell mechanics remains elusive. How intracellular mechanical hindrance, reinforcement, and supports interfere with the cell cycle and promote cell death is described here. Reproducible devices with highly controlled size, shape, and with a broad range of stiffness are internalized in HeLa cells. Once inside, they induce characteristic cell-cycle deviations and promote cell death. Device shape and stiffness are the dominant determinants of mechanical impairment. Device structural support to the cell membrane and centering during mitosis maximize their effects, preventing spindle centering, and correct chromosome alignment. Nanodevices reveal that the spindle generates forces larger than 114 nN which overcomes intracellular confinement by relocating the device to a less damaging position. By using intracellular mechanical drugs, this work provides a foundation to defining the role of intracellular constraints on cell function and fate, with relevance to fundamental cell mechanics and nanomedicine.

Adv. Mater. 2022, 34, 2109581.

Graphene active sensor arrays for chronic, wireless monitoring of wide frequency band epicortical neural activity
Graphene active sensor arrays for long-term and wireless mapping of wide frequency band epicortical brain activity
Garcia-Cortadella, R., Schwesig, G., Jeschke, C., Illa, X., Gray, A.L., Savage, S., Stamatidou, E., Schiessl, I., Masvidal-Codina, E., Kostarelos, K., Guimerà-Brunet, A., Sirota, A., Garrido, J.A.

Graphene active sensors have demonstrated promising capabilities for the detection of electrophysiological signals in the brain. Their functional properties, together with their flexibility as well as their expected stability and biocompatibility have raised them as a promising building block for large-scale sensing neural interfaces. However, in order to provide reliable tools for neuroscience and biomedical engineering applications, the maturity of this technology must be thoroughly studied. Here, we evaluate the performance of 64-channel graphene sensor arrays in terms of homogeneity, sensitivity and stability using a wireless, quasi-commercial headstage and demonstrate the biocompatibility of epicortical graphene chronic implants. Furthermore, to illustrate the potential of the technology to detect cortical signals from infra-slow to high-gamma frequency bands, we perform proof-of-concept long-term wireless recording in a freely behaving rodent. Our work demonstrates the maturity of the graphene-based technology, which represents a promising candidate for chronic, wide frequency band neural sensing interfaces.

Nature Communications, (2021), 12, 1, (211), 10.1038/s41467-020-20546-w

Direct Visualization of Anti-Ferroelectric Switching Dynamics via Electrocaloric Imaging
Direct Visualization of Anti-Ferroelectric Switching Dynamics via Electrocaloric Imaging
Vales-Castro, P., Vellvehi, M., Perpiñà, X., Caicedo, J. M., Jordà, X., Faye, R., Roleder, K., Kajewski, D., Perez-Tomas, A., Defay, E., Catalan, G.

The large electrocaloric coupling in PbZrO3 allows using high-speed infrared imaging for visualizing anti-ferroelectric switching dynamics via the associated temperature change. It is found that in ceramic samples of homogeneous temperature and thickness, switching is fast due to the generation of multiple nucleation sites, with devices responding in the millisecond range. By introducing gradients of thickness, however, it is possible to change the dynamics to propagation limited, whereby a single-phase boundary sweeps across the sample like a cold front, at a speed of ≈20 cm s−1. Additionally, introducing thermostatic temperature differences between two sides of the sample enables the simultaneous generation of a negative electrocaloric effect on one side and a positive one on the other, yielding a Janus-like electrocaloric response.

Advanced Electronic Materials, 2021, 2100380, DOI: 10.1002/aelm.202100380

Gut-on-a-chip: Mimicking and monitoring the human intestine
Gut-on-a-chip: Mimicking and monitoring the human intestine
Marrero, D., Pujol-Vila, F., Vera, D., Gabriel, G., Illa, X., Elizalde-Torrent, A., Alvarez, M., Villa, R.

Over the last few years, the intestine has been extensively studied using in vitro microfluidic systems, commonly known as gut-on-a-chip (GOC) devices. This interest has been due not only to the importance of the intestine's proper functions but also to the relationship that this organ and the microbiota that inhabits it has with the rest of the body's organs. The increased complexity of these in vitro systems, together with the need to improve our understanding of intestinal physiology interdependencies, has led to greater focus on the integration of biosensors within these devices. However, the current number of GOC devices with integrated sensors for monitoring relevant physiological parameters are very limited and demand the use of external analytical techniques that delay the analysis and prevent real-time decision-making. This paper reviews the various materials, technologies, and structures that have been used both for mimicking the physiology of the intestine and monitoring relevant physiological parameters, such as permeability of the gut barrier, dissolved oxygen concentration, cytokines profile and the production of microbial short-chain fatty acids. We also propose alternative biosensing techniques demonstrated in other in vitro and lab-on-a-chip devices that could be translated to GOC models. A critical analysis of the requirements, limitations, and current challenges on the microenvironment replication and monitorization of GOC models is included, with a particular focus on the physiological parameters and biomarkers that should be detected simultaneously in real-time to get a proper framework of the gut function that until now, have not received the necessary attention.

Biosensors and Bioelectronics. Volume 181, 1 June 2021, 113156.

Detail of the microfluidic system, the tissue barrier and the hydrogel
Engineering Tissue Barrier Models on Hydrogel Microfluidic Platforms
Vera, D., García-Díaz, M., Torras, N., Álvarez, M., Villa, R., Martinez, E.

Tissue barriers play a crucial role in human physiology by establishing tissue compartmentalization and regulating organ homeostasis. Combining hydrogels with microfluidics technology provides unique opportunities to better recreate in vitro the tissue barrier models including the cellular components and the functionality of the in vivo tissues. Such platforms have the potential of greatly improving the predictive capacities of the in vitro systems in applications such as drug development, or disease modeling. Nevertheless, their development is not without challenges in their microfabrication. In this review, we will discuss the recent advances driving the fabrication of hydrogel microfluidic platforms and their applications in multiple tissue barrier models.

ACS Appl. Mater. Interfaces 2021, 13, 12, 13920–13933.

Ultrabroadband light absorbing Fe/polymer flexible metamaterial for soft opto-mechanical devices
Ultrabroadband light absorbing Fe/polymer flexible metamaterial for soft opto-mechanical devices
Güell-Grau, P., Pi, F., Villa, R., Nogués, J., Alvarez, M., Sepúlveda, B.

Ultrabroadband light absorbers are attracting increasing interest for applications in energy harvesting, photodetection, self-regulated devices or soft robotics. The developed metamaterial, composed of a nanostructured Fe layer mechanically coupled to a thin polydimethylsiloxane (PDMS) film, shows unprecedented ultrabroadband and angle-independent optical absorption (averaging 84% within 300–18000 nm). The excellent photothermal efficiency and large thermal-expansion mismatch of the metamaterial is efficiently transformed into large mechanical deflections, which we exploit to show an artificial iris that self-regulates the transmitted light power from the ultraviolet to the long-wave infrared, an untethered light-controlled mechanical gripper and a light-triggered electrical switch.

Applied Materials Today, Volume 23, 2021, 101052, ISSN 2352-9407,