Transparent Polydimethylsiloxane Research Articles

Remote-Controlled Mice

What if expression of a light-sensitive protein could be triggered wirelessly, on demand? What if optogenetics and neuropharmacology could be implemented in an untethered, freely moving animal model? Such technology would allow for a plethora of neurobiological experiments that are currently confounded by repeated animal handling, tissue-damaging cannulas, and tangled optical cables. In the July 30 issue of Cell, Jeong and colleagues introduce such a technology. The ultrathin and flexible devices, termed wireless optofluidic probes, enable remote control of drug infusion and optical manipulation in the deep brain regions of freely moving mice engaged in behavioral tasks [Jeong et al., 2015] (see Figure 1). Figure 1 Wireless optofluidic control of mouse behavior. Jeong et al. leveraged the latest advances in microcontact printing techniques and flexible electronics to produce wireless optofluidic probes comprised of multiple functional components. A transparent flexible polydimethylsiloxane (PDMS) ribbon with four drug delivery channels was integrated with a polyethylene terephthalate (PET) filament carrying microscale inorganic light-emitting diodes (μLEDs) previously developed by the same group [Kim et al., 2013]. The resulting probe had an overall thickness of ~ 80 μm, and a low bending stiffness of 13–18 N/m, minimizing the neural tissue damage. The four microfluidic channels were connected to individual reservoirs, allowing each drug to be pumped independently and released on-demand. The optofluidic probe was designed to interface with a battery-powered infrared wireless module that allowed for independent control μLEDs. The individually controlled wireless fluid infusion presents a powerful tool for numerous applications in systems neuroscience and circuit mapping. For example, expression of multiple genes can now be altered wirelessly at different time points using separate viral injection steps. Multiple injections have previously required separate surgeries that compromised animal health, extended recovery time, and produced severe neural tissue damage. The optofluidic probe also allows for multiple behavioral assays to be conducted with a single subject. As a simple proof of principle, authors have demonstrated infusions of a peptide [D-Ala2, N-MePhe4, Gly-ol]-enkephalin (DAMGO), μ-opioid receptor (MOPR) agonist, or a control fluid into the ventral tegmental area (VTA). From a meter away, it was possible to trigger stereotyped rotations in mice, characteristic of unilateral DAMGO delivery into the VTA, while the delivery of control fluid did not induce any notable effect. The combinatorial optical and microfluidic operation of the probes was also demonstrated in a reward-related preference task probing the dopaminergic projection from the ventral tegmental area to the nucleus accumbens shell (NAcSh). The authors implanted their optofluidic probes in the NAcSh of transgenic mice. In these mice, specific expression of Channelrhodopsin 2 (ChR2) in dopaminergic neurons and their processes was established by a separate viral injection into the VTA. By switching the μLEDs on from a distance, the authors were able to remotely activate VTA-to-NAcSh dopaminergic projection and drive real-time place preference. The latter was then abolished by simultaneous wirelessly-triggered infusion of SCH23390, a dopamine receptor D1 antagonist. The probes developed by Jeong and colleagues present a technological leap forward. Future extensions of their technology may include integrated micro-electromechanical systems (MEMS) components such as microfluidic pumps, which should enable multiple injections over the course of long-term in vivo studies. The overall weight and electronic complexity, however, will have to be carefully considered to accommodate experiments in small subjects. Another direction for future improvement could be the incorporation of electrical recording capabilities. Electrophysiology, when combined with behavioral experiments and pharmacological and optogenetic manipulation, would provide a more systematic understanding of both neural circuitry and the brain. Furthermore, incorporation of neural recording is an essential step on the way towards closed-loop systems for effective treatment of neurological and psychiatric disorders [Rosin et al., 2011]. Future directions of wireless integrated neural interface devices will likely take off through multidisciplinary efforts bridging electrical engineering, materials science, mechanical engineering, and bioengineering. Advanced circuit design and microfabrication will enable more complex feedback and control systems. New materials and mechanical platforms are anticipated to yield a versatility of modalities for recording and modulation of neural networks with ever increasing spatial and temporal resolution. Finally, close collaborations between basic neuroscientists and engineers such as the one that led to the development of the optofluidic probes, will be essential to the conception of biologically-relevant technologies for brain mapping as well as future therapies for the diseases of the nervous system.

On-site chip-based colorimetric quantitation of organophosphorus pesticides using an office scanner

Herein we report a scanner-readable plastic microchip for the colorimetric quantitation of organophosphorus (OP) pesticides in food products. The detection principle relies on the irreversible activity inhibition of acetylcholinesterase (AChE) by OP pesticides; AChE catalytically hydrolyzes acetylthiocholine (ATCh) to thiocholine, which in-turn reacts with dithiobis-nitrobenzoic acid (DTNB) to produce a yellow colored product (deprotonated 5-thio-2-nitrobenzoic acid, TNB). The yellow color diminishes upon increasing the concentration of the OP pesticides. In particular, we have fabricated a simple plastic microchip consisting of a transparent polydimethylsiloxane (PDMS) plate with embedded micro-channels (for the colorimetric reaction) attached to a polycarbonate (PC) base plate. A standard flatbed office scanner was used to image the colorimetric reaction at real time, and a commercial photo editing software to read the yellow intensity of the captured images. The detection limit for malathion (one of the most popularly used OP pesticides nowadays) was determined to be 100 ppb, which is below the food safety limits and comparable with conventional spectroscopic detection. The simplicity of the device fabrication and operation of this colorimetric protocol augments its potential for on-site food safety analysis in place of rather expensive and complex spectrometer-based methods.

Conveyance of helium–neon laser, polymer liquid and polystyrene (PS) beads through microoptofluidic channels of polydimethylsiloxane (PDMS)

In this work, the simultaneous conveyance of light, liquid, and microbeads in microoptofluidic channels was investigated experimentally. Based on soft lithography, the microoptofluidic channels were made of transparent polydimethylsiloxane (PDMS) with length of ~3 cm, height of ~134 μm, width of ~210 μm, and refractive index of light (n) of 1.41–1.42. These channels were intended to have the different bent angles (θb) from 15° to 90° and radii (R) of curvature from 0 to 10 mm, respectively. The colorless liquid polymer of Norland Optical Adhesive (NOA 89) was used as the core material of the channels. The NOA 89 had a higher n than that of PDMS to be capable of generating the total internal reflection of light with a collective angle (θcollect) 20°–21° and numerical aperture ~0.54. Using helium–neon (HeNe) red laser at a wavelength of 633 nm, the characterization of optical illumination showed that the optical losses of LCWs strongly depended on their bending degree with 0.056–0.060 dB/cm°. Finally, we demonstrated the motion of light delivered by microfluidic flows at an average speed of ~1 mm/s and the motion of 20-μm-diameter polystyrene beads at a flowing speed ~5 μm/s. The developed LCWs here may be further realized for a promising application on tracking and visualization of small objects such as cells within biological microsystems in the future.

Polydimethylsiloxane template-based size-selective assembly of single biological cells

This paper presents experimental demonstrations of size-selective parallel templated assembly of single biological cells on a polydimethylsiloxane (PDMS) template. Using the ultrasonic assembly technique known as templated assembly by selective removal (TASR), single chlorella cells with diameters between 5 and 20 μm were individually assembled in parallel with high size-based selectivity and precise alignment into their size-matching hemispherical assembly sites on the template. Optical observation of assembled single cells on the template without cell staining was enabled by transparency of the PDMS template. No significant change in the cell morphology was observed after assembly, confirming that the conditions of ultrasound used in the assembly are compatible. The presented size-selective trapping of single biological cells on the transparent and biocompatible PDMS template represents a biological tool with potential for direct implementation in various biological applications including cell sorting and isolation for optical cell diagnostics or cell templating for artificial tissue replication.

Dynamic daylight control system implementing thin cast arrays of polydimethylsiloxane-based millimeter-scale transparent louvers

The deep building layouts typical in the U.S. have led to a nearly complete reliance on artificial lighting in standard office buildings. The development of daylight control systems that maximize the penetration and optimize the distribution of natural daylight in buildings has the potential for saving a significant portion of the energy consumed by artificial lighting, but existing systems are either static, costly, or obstruct views towards the outside. We report the Dynamic Daylight Control System (DDCS) that integrates a thin cast transparent polydimethylsiloxane (PDMS)-based deformable array of louvers and waveguides within a millimeter-scale fluidic channel system. This system can be dynamically tuned to the different climates and sun positions to control daylight quality and distribution in the interior space. The series of qualitative and quantitative tests confirmed that DDCS exceeds conventional double glazing system in terms of reducing glare near the window and distributing light to the rear of the space. The system can also be converted to a visually transparent or a translucent glazing by filling the channels with an appropriate fluid. DDCS can be integrated or retrofitted to conventional glazing systems and allow for diffusivity and transmittance control.

Fabricating low cost and high performance elastomer lenses using hanging droplets.

Existing methods for low cost lenses using parallel mold stamping and high temperature reflow requires complex engineering controls to produce high quality lenses. These manufacturing techniques rely on expensive equipment. In this paper, we propose a low cost (< $ 0.01 per pc) flexible moldless lens fabrication method based on curing a hanging transparent polydimethylsiloxane (PDMS) elastomer droplet on a curved substrate. Additional deposition of hanging droplets in the same manner led to a substantial increase in the lens curvature and concomitant decrease in the focal length of the PDMS lenses down to ~2 mm. The shortest focal length lenses were shown to collimate light from a bare light emitting diode (LED) and image microscopic structures down to around 4 µm with 160x magnification. Our hanging droplet lens fabrication technique heralds a new paradigm in the manufacture of low cost, high performance optical lenses for the masses. Using these lenses, we were able to transform an ordinary commercial smartphone camera into a low-cost digital dermascope (60x magnification) that can readily visualize microscopic structures on skin such as sweat pores.

High-efficiency transfer of percolating nanowire films for stretchable and transparent photodetectors.

Stretchable devices with good transparency offer exciting new applications over the existing technologies, but remarkable difficulties remain in the fabrication of transparent and stretchable devices. In this paper, we report an effective method to fabricate transparent elastic photodetectors which combines the merits of the transparent polydimethylsiloxane (PDMS) polymer with its stretchability and the Zn₂SnO₄ nanowire (NW) with its photodetection functionality. Zonyl fluorosurfactant is found to be critical which improves the bonding between the functional NWs and the PDMS matrix, thus enabling the high efficient transfer of NW structures into PDMS. Highly conductive and thin percolating AgNW films were successfully embedded into PDMS mixed with ∼11% Zonyl which are otherwise not achievable with pure PDMS. Transparent and stretchable photodetectors were fabricated with the developed method. The photocurrent was found to be reciprocal to the square of the channel length, Iph∼ 1/l(2). The chemically bonded sensing materials in the PDMS matrix allow more NW exposure to air. This lead to a fast switching operation of the photodetectors with a response time below 0.8 s and a reset time around 3 s, which is significantly improved compared to reported stretchable NW photodetectors fully embedded in the polymer matrix.

Pressure-driven deformation with soft polydimethylsiloxane (PDMS) by a regular syringe pump: challenge to the classical fluid dynamics by comparison of experimental and theoretical results

Pressure-driven flows through optically transparent polydimethylsiloxane (PDMS) microfluidic channels using a syringe pump are common in many experimental applications. However, because of small changes, the pressure-induced deformations due to soft materials and shapes and patterns in the microchannels, which generate untargeted flow velocity and pressure drop, have been easily ignored. In this paper, we present a simple experimental investigation with circular-shaped, periodically arranged objects of three different characteristic dimensions, as well as various channel heights ranging from 15 μm to 200 μm. The resultant CCD images and pressure data were used to determine the extent of the start-up transients and evaluate the establishment of quasi-steady flow conditions. Channel deformation, measured by fluorescence intensity difference, was severe in shallow microchannels that had characteristically large obstacles. In addition, PDMS microchannel bulging effects in shallow microchannels exerted a greater deleterious effect on (ΔP/Δx)QS values than upon VQS for the experiments using a volumetrically controlled syringe pump. The discrepancy between experimental and theoretical (ΔP/Δx) increased with decreasing microchannel height. This means that the severe PDMS bulging observed in shallow microchannels using a syringe pump can generate large deviations from the desired experimental result. As a result, the slope of Darcy friction factors plotted against the Reynolds number indicates that the slope was strongly dependent on microfluidic channel height and the degree of PDMS bulging. The microfluidic channel with the greatest height exhibited the smallest bulging effect and was shown to be in relatively good agreement with predicted values, while the slope became much steeper than −1 as channel heights decreased.

Quantitative and Temporal Control of Oxygen Microenvironment at the Single Islet Level

Simultaneous oxygenation and monitoring of glucose stimulus-secretion coupling factors in a single technique is critical for modeling pathophysiological states of islet hypoxia, especially in transplant environments. Standard hypoxic chamber techniques cannot modulate both stimulations at the same time nor provide real-time monitoring of glucose stimulus-secretion coupling factors. To address these difficulties, we applied a multilayered microfluidic technique to integrate both aqueous and gas phase modulations via a diffusion membrane. This creates a stimulation sandwich around the microscaled islets within the transparent polydimethylsiloxane (PDMS) device, enabling monitoring of the aforementioned coupling factors via fluorescence microscopy. Additionally, the gas input is controlled by a pair of microdispensers, providing quantitative, sub-minute modulations of oxygen between 0-21%. This intermittent hypoxia is applied to investigate a new phenomenon of islet preconditioning. Moreover, armed with multimodal microscopy, we were able to look at detailed calcium and KATP channel dynamics during these hypoxic events. We envision microfluidic hypoxia, especially this simultaneous dual phase technique, as a valuable tool in studying islets as well as many ex vivo tissues.

Fabrication of Optically Transparent PDMS Artificial Lotus Leaf Film Using Underexposed and Underbaked Photoresist Mold

We report an extremely simple method of making an optically transparent superhydrophobic polydimethyl-siloxane (PDMS) thin film using underexposed and underbaked positive photoresist (PR) mold. Significant under soft-bake condition makes PR retain good amount of solvents, which greatly increases the dissolution rate of the PR during developing. A combination of optimal underbaking and underexposure condition created a unique hierarchical micro-/nano- structure on the PR mold, and inverse image of the PR mold was replicated to create a hierarchical micro/nano structured broccoli-shaped PDMS thin film. A 100-nm-thick fluorocarbon film was optionally deposited on the broccoli-shaped PDMS film to further enhance superhydrophobicity. Advancing and receding angles of the film for 4- μL water droplet were found to be 161.33±0.763° and 133.33±0.29°, respectively, showing superhydrophobicity. It was also found that the optical transmittance at around 550 nm for this PDMS film was approximately 90%.

Deformation properties between fluid and periodic circular obstacles in polydimethylsiloxane microchannels: Experimental and numerical investigations under various conditions

Understanding the mechanical properties of optically transparent polydimethylsiloxane (PDMS) microchannels was essential to the design of polymer-based microdevices. In this experiment, PDMS microchannels were filled with a 100 μM solution of rhodamine 6G dye at very low Reynolds numbers (∼10(-3)). The deformation of PDMS microchannels created by pressure-driven flow was investigated by fluorescence microscopy and quantified the deformation by the linear relationship between dye layer thickness and intensity. A line scan across the channel determined the microchannel deformation at several channel positions. Scaling analysis widely used to justify PDMS bulging approximation was allowed when the applied flow rate was as high as 2.0 μl/min. The three physical parameters (i.e., flow rate, PDMS wall thickness, and mixing ratio) and the design parameter (i.e., channel aspect ratio = channel height/channel width) were considered as critical parameters and provided the different features of pressure distributions within polymer-based microchannel devices. The investigations of the four parameters performed on flexible materials were carried out by comparison of experiment and finite element method (FEM) results. The measured Young's modulus from PDMS tensile test specimens at various circumstances provided reliable results for the finite element method. A thin channel wall, less cross-linker, high flow rate, and low aspect ratio microchannel were inclined to have a significant PDMS bulging. Among them, various mixing ratios related to material property and aspect ratios were one of the significant factors to determine PDMS bulging properties. The measured deformations were larger than the numerical simulation but were within corresponding values predicted by the finite element method in most cases.

Flexible PDMS electrode for one-point wearable wireless bio-potential acquisition

This work presents a flexible poly-dimethylsiloxane (PDMS) electrode for a one-point, wearable, wireless bio-potential acquisition device. The proposed device measures electrocardiogram (ECG) signals and removes cumbersome wires from a general ECG monitoring system. A novel flexible PDMS dry electrode (FPDE) is constructed with Au as a contact layer in bio-compatible with skin and PDMS. However, PDMS has exhibited stability limit in Au deposition and patterning. This limitation is solved by the surface treatment of PDMS via CO2 laser to increase surface roughness from nm to μm scale. The laser treatment method can increase the adhesion ratio by up to 57% (max.), subsequently allowing for Au to be stably adhered on PDMS by physical deposition and patterning. This work also develops a simple technology to fabricate FPDEs by adopting polyimide film as the mask made with CO2 laser capable of reducing cost and reusable for metal patterning applications. Furthermore, a front-end acquisition circuit and a wireless ZigBee module are integrated and packaged by flexible and transparent PDMS cover with three-pad FPDEs into a novel one-point, wearable, wireless ECG acquisition device. Importantly, the proposed device can obtain ECG signals efficiently with comfortable skin touch.

Bioengineered bioluminescent magnetotactic bacteria as a powerful tool for chip-based whole-cell biosensors

This paper describes the generation of genetically engineered bioluminescent magnetotactic bacteria (BL-MTB) and their integration into a microfluidic analytical device to create a portable toxicity detection system. Magnetospirillum gryphiswaldense strain MSR-1 was bioengineered to constitutively express a red-emitting click beetle luciferase whose bioluminescent signal is directly proportional to bacterial viability. The magnetic properties of these bacteria have been exploited as "natural actuators" to transfer the cells in the chip from the reaction to the detection area, optimizing the chip's analytical performance. A robust and cost-effective biosensor for the evaluation of sample toxicity, named MAGNETOX, based on lens-free contact imaging detection, has been developed. A microfluidic chip has been fabricated using multilayered black and transparent polydimethyl siloxane (PDMS) in which BL-MTB are incubated for 30 min with the sample, then moved by microfluidics, trapped, and concentrated in detection chambers by an array of neodymium-iron-boron magnets. The chip is placed in contact with a cooled CCD via a fiber optic taper to perform quantitative bioluminescence imaging after addition of luciferin substrate. A model toxic compound (dimethyl sulfoxide, DMSO) and a bile acid (taurochenodeoxycholic acid, TCDCA) were used to investigate the analytical performance of the MAGNETOX. Incubation with DMSO and TCDCA drastically reduces the bioluminescent signal in a dose-related manner. The generation of bacteria that are both magnetic and bioluminescent combines the advantages of easy 2D cell handling with ultra sensitive detection, offering undoubted potential to develop cell-based biosensors integrated into microfluidic chips.

Strain induced chemical potential difference between monolayer graphene sheets

Monolayer graphene sheets were deposited on a transparent and flexible polydimethylsiloxane (PDMS) substrate, and a tensile strain was loaded by stretching the substrate in one direction. It was found that an electric potential difference between stretched and static monolayer graphene sheets reached 8 mV when the strain was 5%. Theoretical calculations for the band structure and total energy revealed an alternative way to experimentally tune the band gap of monolayer graphene, and induce the generation of electricity.

Wafer-Scale Pattern Transfer of Metal Nanostructures on Polydimethylsiloxane (PDMS) Substrates via Holographic Nanopatterns

In this paper, we report on a cost-effective and simple, nondestructive pattern transfer method that allows the fabrication of metallic nanostructures on a polydimethylsiloxane (PDMS) substrate on a wafer scale. The key idea is to use holographic nanopatterns of a photoresist (PR) layer as template structures, where a metal film is directly deposited in order to replicate the nanopatterns of the PR template layer. Then, the PDMS elastomer is molded onto the metal film and the metal/PDMS composite layer is directly peeled off from the PR surface. Many metallic materials including Ti, Al, and Ag were successfully nanopatterned on PDMS substrates by the pattern transfer process with no use of any adhesion promoter layer or coating. In case of Au that has poor adhesion to PDMS material, a salinization of the metal surface with 3-(aminopropyl)-triethoxysilane (APTES) monolayer promoted the adhesion and led to successful pattern transfer. A series of adhesion tests confirmed the good adhesion of the transferred metal films onto the molded PDMS substrates, including scotch-tape and wet immersion tests. The inexpensive and robust pattern transfer approach of metallic nanostructures onto transparent and flexible PDMS substrates will open the new door for many scientific and engineering applications such as micro-/nanofluidics, optofluidics, nanophotonics, and nanoelectronics.

Fabrication method of double-slit-grating for high resolution microspectrometers

In this paper, a double-slit-grating (DSG) is presented for improving the spectral resolution of microspectrometer. We try to develop a simple and low-cost fabrication method by synthetically using the interference lithography, ion etching technique and localized surface plasmon imaging lithography: A grating was first obtained with traditional interference lithography, and then it was copied by using transparent material polydimethylsiloxane (PDMS) to form a soft mask, which can contact the silver superlens firmly, and finally the DSG will be fabricated though localized surface plasmon imaging lithography. This double-slit-grating can enhance the spectral resolution of microspectrometers to 0.1nm level. DSG made of metal has rich spectral characteristics and spectral sensibility, which makes it suitable for biomedical sensors.

Active glass–polymer superlattice structure for photonic integration

We propose an all-laser processing approach allowing controlled growth of organic–inorganic superlattice structures of rare-earth ion doped tellurium-oxide-based glass and optically transparent polydimethyl siloxane (PDMS) polymer; the purpose of which is to illustrate the structural and thermal compatibility of chemically dissimilar materials at the nanometer scale. Superlattice films with interlayer thicknesses as low as 2 nm were grown using pulsed laser deposition (PLD) at low temperatures (100 °C). Planar waveguides were successfully patterned by femtosecond-laser micro-machining for light propagation and efficient Er3+-ion amplified spontaneous emission (ASE). The proposed approach to achieve polymer–glass integration will allow the fabrication of efficient and durable polymer optical amplifiers and lossless photonic devices. The all-laser processing approach, discussed further in this paper, permits the growth of films of a multitude of chemically complex and dissimilar materials for a range of optical, thermal, mechanical and biological functions, which otherwise are impossible to integrate via conventional materials processing techniques.

Solvothermal Synthesis of Nanoporous Polymer Chalk for Painting Superhydrophobic Surfaces

Reported here is a facile synthesis of nanoporous polymer chalk for painting superhydrophobic surfaces. Taking this nanoporous polymer as a media, superhydrophobicity is rapidly imparted onto three typical kinds of substrates, including paper, transparent polydimethylsiloxane (PDMS), and finger skin. Quantitative characterization showed that the adhesion between the water droplet and polymer-coated substrates decreased significantly compared to that on the original surface, further indicating the effective wetting mode transformation. The nanoporous polymer coating would open a new door for facile, rapid, safe, and larger scale fabrication of superhydrophobic surfaces on general substrates.

Bromo-oxidation reaction in enzyme-entrapped alginate hollow microfibers

In this article, the authors present the fabrication of an enzyme-entrapped alginate hollow fiber using a microfluidic device. Further use of enzyme-entrapped alginate hollow fibers as a biocatalytic microchemical reactor for chemical synthesis is also deliberated in this article. To ensure that there is no enzyme leaching from the fiber, fiber surfaces were coated with chitosan. To confine the mobility of reactants and products within the porous hollow fibers the entire fibers were embedded into a transparent polydimethylsiloxane (PDMS) matrix which also works as a support matrix. A vanadium-containing bromoperoxidase enzyme isolated from Corallina confusa was used as a model enzyme to demonstrate the use of these alginate hollow-fiber reactors in bromo-oxidation of phenol red to bromophenol blue at different dye flow rates. Stability of the entrapped enzyme at different temperatures and the effect of the chitosan coating on the reaction conversion were also studied. It was observed that molecules as big as 27 kDa can be retained in the matrix after coating with chitosan while molecules with molecular-weight of around 378 Da can still diffuse in and out of the matrix. The kinetic conversion rate in this microfluidic bioreactor was more than 41-fold faster when compared with the standard test-tube procedure.

Optical and Sensing Properties of 1-Pyrenecarboxylic Acid-Functionalized Graphene Films Laminated on Polydimethylsiloxane Membranes

We present fabrication and characterization of macroscopic thin films of graphene flakes, which are functionalized with 1-pyrenecarboxylic acid (PCA) and are laminated onto flexible and transparent polydimethylsiloxane (PDMS) membranes. The noncovalently (π-stacked) functionalization of PCA allows us to obtain a number of unique optical and molecular sensing properties that are absent in pristine graphene films, without sacrificing the conducting nature of graphene. The flexible PCA-graphene-PDMS hybrid structure can block 70-95% of ultraviolet (UV) light, while allowing 65% or higher transmittance in the visible region, rendering them potentially useful for a number of flexible UV absorbing/filtering applications. In addition, the electrical resistance of these structures is found to be sensitive to the illumination of visible light, atmospheric pressure change, and the presence of different types of molecular analytes. Owing to their multifunctionality, these hybrid structures have immense potential for the development of versatile, low-cost, flexible, and portable electronic and optoelectronic devices for diverse applications.