Biofunctionalized all-polymer photonic lab on a chip with integrated solid-state light emitter

A photonic lab on a chip (PhLOC), comprising a solid-state light emitter (SSLE) aligned with a biofunctionalized optofluidic multiple internal reflection (MIR) system, is presented. The SSLE is obtained by filling a microfluidic structure with a phenyltrimethoxysilane (PhTMOS) aqueous sol solution containing a fluorophore organic dye. After curing, the resulting xerogel solid structure retains the emitting properties of the fluorophore, which is evenly distributed in the xerogel matrix. Photostability studies demonstrate that after a total dose (at l = 365 nm) greater than 24 J/cm2, the xerogel emission decay is only 4.1%. To re-direct the emitted light, the SSLE includes two sets of air mirrors that surround the xerogel. Emission mapping of the SSLE demonstrates that alignment variations of 150 mm (between the SSLE and the external pumping light source) provide fluctuations in emitted light smaller than 5%. After this verification, the SSLE is monolithically implemented with a MIR, forming the PhLOC. Its performance is assessed by measuring quinolone yellow, obtaining a limit of detection (LOD) of (0.60 +/- 0.01) mM. Finally, the MIR is selectively biofunctionalized with horseradish peroxidase (HRP) for the detection of hydrogen peroxide (H2O2) target analyte, obtaining a LOD of (0.7 +/- 0.1) mM for H2O2, confirming, for the first time, that solid-state xerogel-based emitters can be massively implemented in biofunctionalized PhLOCs

Carbon nanotube neurotransistors with ambipolar memory and learning functions

In recent years, neuromorphic computing has gained attention as a promising approach to enhance computing efficiency. Among existing approaches, neurotransistors have emerged as a particularly promising option as they accurately represent neuron structure, integrating the plasticity of synapses along with that of the neuronal membrane. An ambipolar character could offer designers more flexibility in customizing the charge flow to construct circuits of higher complexity. We propose a novel design for an ambipolar neuromorphic transistor, utilizing carbon nanotubes as the semiconducting channel and an ion-doped sol-gel as the polarizable gate dielectric. Due to its tunability and high dielectric constant, the sol-gel effectively modulates the conductivity of nanotubes, leading to efficient and controllable short-term potentiation and depression. Experimental results indicate that the proposed design achieves reliable and tunable synaptic responses with low power consumption. Our findings suggest that the method can potentially provide an efficient solution for realizing more adaptable cognitive computing systems.Comment: 16 pages, 6 pages of supporting information at the end, 6 main figures, 10 supporting figure

Real-Time Tracking of Individual Droplets in Multiphase Microfluidics

Multiphase microfluidics enables the high-throughput manipulation of droplets for multitude of applications, from the confined fabrication of nano- and micro-objects to the parallelization of chemical reactions of biomedical or biological interest. While the standard methods to follow droplets on a chip are represented by a visual observation through either optical or fluorescence microscopy, the conjunction of microfluidic platforms with miniaturized transduction mechanisms opens new ways towards the real-time and individual tracking of each independent reactor. Here we provide an overview of the most recent droplet sensing techniques, with a special focus on those based on electrical signals for an optics-less analysis

Electrochemically Exfoliated High-Quality 2H-MoS₂ for Multiflake Thin Film Flexible Biosensors

2D molybdenum disulfide (MoS₂) gives a new inspiration for the field of nanoelectronics, photovoltaics, and sensorics. However, the most common processing technology, e.g., liquid‐phase based scalable exfoliation used for device fabrication, leads to the number of shortcomings that impede their large area production and integration. Major challenges are associated with the small size and low concentration of MoS₂ flakes, as well as insufficient control over their physical properties, e.g., internal heterogeneity of the metallic and semiconducting phases. Here it is demonstrated that large semiconducting MoS₂ sheets (with dimensions up to 50 µm) can be obtained by a facile cathodic exfoliation approach in nonaqueous electrolyte. The synthetic process avoids surface oxidation thus preserving the MoS₂ sheets with intact crystalline structure. It is further demonstrated at the proof‐of‐concept level, a solution‐processed large area (60 × 60 µm) flexible Ebola biosensor, based on a MoS₂ thin film (6 µm thickness) fabricated via restacking of the multiple flakes on the polyimide substrate. The experimental results reveal a low detection limit (in femtomolar–picomolar range) of the fabricated sensor devices. The presented exfoliation method opens up new opportunities for fabrication of large arrays of multifunctional biomedical devices based on novel 2D materials

Two-Dimensional Boronate Ester Covalent Organic Framework Thin Films with Large Single Crystalline Domains for a Neuromorphic Memory Device

Despite the recent progress in the synthesis of crystalline boronate ester covalent organic frameworks (BECOFs) in powder and thin-film through solvothermal method and on-solid-surface synthesis, respectively, their applications in electronics, remain less explored due to the challenges in thin-film processability and device integration associated with the control of film thickness, layer orientation, stability and crystallinity. Moreover, although the crystalline domain sizes of the powder samples can reach micrometer scale (up to ≈1.5 μm), the reported thin-film samples have so far rather small crystalline domains up to 100 nm. Here we demonstrate a general and efficient synthesis of crystalline two-dimensional (2D) BECOF films composed of porphyrin macrocycles and phenyl or naphthyl linkers (named as 2D BECOF-PP or 2D BECOF-PN) by employing a surfactant-monolayer-assisted interfacial synthesis (SMAIS) on the water surface. The achieved 2D BECOF-PP is featured as free-standing thin film with large single-crystalline domains up to ≈60 μm2 and tunable thickness from 6 to 16 nm. A hybrid memory device composed of 2D BECOF-PP film on silicon nanowire-based field-effect transistor is demonstrated as a bio-inspired system to mimic neuronal synapses, displaying a learning–erasing–forgetting memory process. © 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA

Applications of nanogenerators for biomedical engineering and healthcare systems

The dream of human beings for long living has stimulated the rapid development of biomedical and healthcare equipment. However, conventional biomedical and healthcare devices have shortcomings such as short service life, large equipment size, and high potential safety hazards. Indeed, the power supply for conventional implantable device remains predominantly batteries. The emerging nanogenerators, which harvest micro/nanomechanical energy and thermal energy from human beings and convert into electrical energy, provide an ideal solution for self‐powering of biomedical devices. The combination of nanogenerators and biomedicine has been accelerating the development of self‐powered biomedical equipment. This article first introduces the operating principle of nanogenerators and then reviews the progress of nanogenerators in biomedical applications, including power supply, smart sensing, and effective treatment. Besides, the microbial disinfection and biodegradation performances of nanogenerators have been updated. Next, the protection devices have been discussed such as face mask with air filtering function together with real‐time monitoring of human health from the respiration and heat emission. Besides, the nanogenerator devices have been categorized by the types of mechanical energy from human beings, such as the body movement, tissue and organ activities, energy from chemical reactions, and gravitational potential energy. Eventually, the challenges and future opportunities in the applications of nanogenerators are delivered in the conclusive remarks. The combination of nanogenerator and biomedicine have been accelerating the development of self‐powered biomedical devices, which show a bright future in biomedicine and healthcare such as smart sensing, and therapy

Applications of 2D-layered palladium diselenide and its van der Waals heterostructures in electronics and optoelectronics

The rapid development of two-dimensional (2D) transition-metal dichalcogenides has been possible owing to their special structures and remarkable properties. In particular, palladium diselenide (PdSe2) with a novel pentagonal structure and unique physical characteristics have recently attracted extensive research interest. Consequently, tremendous research progress has been achieved regarding the physics, chemistry, and electronics of PdSe2. Accordingly, in this review, we recapitulate and summarize the most recent research on PdSe2, including its structure, properties, synthesis, and applications. First, a mechanical exfoliation method to obtain PdSe2 nanosheets is introduced, and large-area synthesis strategies are explained with respect to chemical vapor deposition and metal selenization. Next, the electronic and optoelectronic properties of PdSe2 and related heterostructures, such as field-effect transistors, photodetectors, sensors, and thermoelectric devices, are discussed. Subsequently, the integration of systems into infrared image sensors on the basis of PdSe2 van der Waals heterostructures is explored. Finally, future opportunities are highlighted to serve as a general guide for physicists, chemists, materials scientists, and engineers. Therefore, this comprehensive review may shed light on the research conducted by the 2D material community.Web of Science131art. no. 14

Applications of nanogenerators for biomedical engineering and healthcare systems

The dream of human beings for long living has stimulated the rapid development of biomedical and healthcare equipment. However, conventional biomedical and healthcare devices have shortcomings such as short service life, large equipment size, and high potential safety hazards. Indeed, the power supply for conventional implantable device remains predominantly batteries. The emerging nanogenerators, which harvest micro/nanomechanical energy and thermal energy from human beings and convert into electrical energy, provide an ideal solution for self-powering of biomedical devices. The combination of nanogenerators and biomedicine has been accelerating the development of self-powered biomedical equipment. This article first introduces the operating principle of nanogenerators and then reviews the progress of nanogenerators in biomedical applications, including power supply, smart sensing, and effective treatment. Besides, the microbial disinfection and biodegradation performances of nanogenerators have been updated. Next, the protection devices have been discussed such as face mask with air filtering function together with real-time monitoring of human health from the respiration and heat emission. Besides, the nanogenerator devices have been categorized by the types of mechanical energy from human beings, such as the body movement, tissue and organ activities, energy from chemical reactions, and gravitational potential energy. Eventually, the challenges and future opportunities in the applications of nanogenerators are delivered in the conclusive remarks.Web of Science4

Monolithically integrated polymeric Lab-on- (Bio)Chips with photonic/electrochemical detection

En esta Tesis de Doctorado se han desarrollado sistemas lab-on-a-chip (LOC) funcionalizados de bajo coste para su uso como herramientas analíticas en aplicaciones medio ambientales y biomédicas. Inicialmente se exploró el potencial de LOCs fotónicos (PhLOC) previamente definidos en nuestro grupo, como sistemas en análisis. Se aplicaron sistemas microfluídicos de Reflexión Interna Múltiple (MIR) fabricados en polímeros de bajo coste, como polydimetilsiloxano (PDMS), siguiendo un procedimiento rápido de fabricación, en la detección de diferentes analitos (células e iones de metales pesados) y su funcionamiento se comparó con el de otras técnicas analíticas más convencionales. Para dotar de selectividad a los PhLOCs se desarrollaron y compararon diferentes protocolos de modificación de superficies para la inmovilización de proteínas en los materiales poliméricos utilizados para la fabricación de estos sistemas. Estos métodos mantienen inalteradas las propiedades ópticas y estructurales del material. Se utilizó la peroxidasa de rábano (HRP) como proteína modelo para estos estudios, y las superficies biofuncionalizadas resultantes se testaron mediante la medición de la actividad enzimática en la reacción de reducción de peróxido de hidrógeno en presencia del mediador redox 2,2’azino-bis (3-ethylbenzthiazoline-6-sulfonic acid) (ABTS), cuyo producto enzimático de color verde pudo ser detectado mediante medidas de absorbancia. Se midió la robustez del proceso de inmovilización mediante la medida de la actividad del HRP durante un periodo superior a un mes. Finalmente, se añadieron nuevos componentes fluídicos y funcionalidades a los PhLOCs previamente aplicados para mejorarsu desempeño. Estructuras microfluídicas tales como mezcladores biofuncionalizados (actuando en consecuencia como reactores) se integraron monolíticamente con el MIR, dando lugar a un PhLOC con mejores prestaciones analíticas. Estos nuevos elementos disminuyeron el tiempo de análisis y el volumen de muestra y reactivo. Con la integración de una celda electroquímica de oro en el substrato, se desarrolló un LOC con lectura de medida dual (DLOC), que permitió la transducción simultánea óptica y electroquímica e hizo el sistema desarrollado autoverificable, mejorando así su fiabilidad. Se mostró el potencial de este DLOC mediante el desarrollo de una herramienta analítica para la medida de glucosa. Se inmovilizaron glucosa oxidasa (GOx) y HRP siguiendo el protocolo desarrollado en esta Tesis y se aplicaron como receptores específicos para la detección de glucosa basada en una reacción enzimática en cascada utilizando el mediador redox ABTS. Como estudio adicional, se testó la aplicabilidad del protocolo de funcionalización en diferentes polímeros y también se llevó a cabo la inmovilización de componentes biológicos diferentes a enzimas.In this PhD Thesis low-cost functionalized Lab-on-(bio)Chip systems (LOC) for their use as analytical tools for environmental and biomedical applications have been developed. Based on photonic LOC approaches (PhLOC) previously defined in our group, the potential of these devices in analysis was explored first. Multiple Internal Reflection (MIR) optofluidic systems made of cost-effective polymers, such as polydimethylsiloxane (PDMS), using rapid fabrication processes were applied for the detection of different analytes (cells and heavy metal ions) and their performance compared with other more conventional analytical techniques. In order to confer selectivity to the PhLOCs, different surface modification protocols for protein immobilization on the polymeric materials used in this work were developed and compared. These methods keep the optical and structural properties of the material unaltered. Horseradish peroxidase (HRP) was chosen as a model protein in these studies, and the resulting biofunctionalized surfaces tested by measuring the enzymatic activity to hydrogen peroxide in the presence of 2,2’azino-bis (3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) redox mediator, whose green colored enzymatic product could be detected by absorbance measurements. The stability of the immobilized HRP was also tested for periods longer than one month. Finally, other fluidic components and functionalities were added to the previously applied PhLOCs in order to enhance their performance. Microfluidic structures such as biofunctionalized mixers (therefore also playing the role of reactors) were monolithically integrated with a MIR, resulting in a PhLOC with enhanced analytical performance. These new elements decreased the analysis time and sample / reagent volumes. With the integration of a gold electrochemical cell in the substrate, a dual readout LOC (DLOC) was developed, which enabled simultaneous optical and electrochemical transduction and made the developed system self-verifying, thereby improving its reliability. The potential of this DLOC was shown by developing an analytical tool for measuring glucose. Glucose oxidase (GOx) and HRP were immobilized following the protocol developed in this Thesis and applied as the specific receptors for the detection of glucose based on an enzymatic cascade reaction also using ABTS redox mediator. As an additional study, the applicability of the developed functionalization protocol was tested on different polymers and the immobilization of biological components other than enzymes was also carried out