Photonic Hydrogel Research Articles

Free-standing molecularly imprinted photonic hydrogels based on β-cyclodextrin for the visual detection of l-tryptophan

Molecularly imprinted photonic hydrogels fabricated by a colloidal crystal template method have been exfoliated from the substrate to get a free-standing film.

Photonic Crystal-Based Sensing and Imaging of Potassium Ions

We report on a method for selective optical sensing and imaging of potassium ions using a sandwich assembly composed of layers of photonic crystals and an ion-selective membrane. This represents a new scheme for sensing ions in that an ionic strength-sensitive photonic crystal hydrogel layer is combined with a K+-selective membrane. The latter consists of plasticized poly(vinyl chloride) doped with the K+-selective ion carrier, valinomycin. The film has a red color if immersed into plain water, but is green in 5 mM KCl and purple at KCl concentrations of 100 mM or higher. This 3D photonic crystal sensor responds to K+ ions in the 1 to 50 mM concentration range (which includes the K+ concentration range encountered in blood) and shows high selectivity over ammonium and sodium ions. Sensor films were also imaged with a digital camera by exploiting the RGB technique.

Effect of Electric Fields on the Hydrogel-Photonic Gel Hybrid Device

Poly(styrene-b-2-vinyl pyridine) (PS-b-P2VP) lamellar film of alternating hydrophobic block-hydrophilic polyelectrolyte block (52 kg/mol-b-57 kg/mol) were fabricated on ITO glass for photonic gel films. Poly(acrylamide-co-acrylic acid) (PAAm-co-PAAc) with potassium salts were synthesized for hydrogel with flat and tetragonal shape. The hydrogel-photonic gel hybrid devices were fabricated with photonic gel layer and hydrogel layer between two electrodes. The reflected wavelength of the cell was changed under electric fields. This experiment showed the effect of electric fields on the hydrogel-photonic gel hybrid devices. The maximum reflectance wavelength of the hybrid device was shifted from 563 nm to 590 nm during electric fields generating time of 25 min. This work shows that reflection color of photonic film can be tuned with hydrogel and electric fields.

Mechano-actuated ultrafast full-colour switching in layered photonic hydrogels.

Photonic crystals with tunability in the visible region are of great interest for controlling light diffraction. Mechanochromic photonic materials are periodically structured soft materials designed with a photonic stop-band that can be tuned by mechanical forces to reflect specific colours. Soft photonic materials with broad colour tunability and fast colour switching are invaluable for application. Here we report a novel mechano-actuated, soft photonic hydrogel that has an ultrafast-response time, full-colour tunable range, high spatial resolution and can be actuated by a very small compressive stress. In addition, the material has excellent mechanical stability and the colour can be reversibly switched at high frequency more than 10,000 times without degradation. This material can be used in optical devices, such as full-colour display and sensors to visualize the time evolution of complicated stress/strain fields, for example, generated during the motion of biological cells.

Band gap control using electric field of photonic gel cells fabricated with block copolymer and hydrogel.

Optical and electrical characteristics of the devices using photonic gel film and hydrogel electrolyte were studied. Poly(styrene-b-2-vinylpyridine) (PS-b-P2VP) lamellar film with alternating hydrophobic block and hydrophilic polyelectrolyte block polymers (52 kg/mol-b-57 kg/mol) were prepared for the photonic gel. Poly(isobutylene-co-maleic acid) sodium salts were prepared for the hydrogel. This hydrogel fiber is common water swelling material and it owned ions for a device has conductivity. Photonic gel and hydrogel was spin coating onto Indium-tin-oxide (ITO) glass for make electric fields. The reflectance maximum wavelength of photonic crystal device shifted from 538 nm and reached to 557 nm, 585 nm and 604 nm during 30 min voltage applying time. The bandwidth variation was very limited. Loss of electrolyte was much less with hydrogel compared to the pure water. We can control color of hydrogel used photonic device by electric field with reasonable time range under moderate electric field by applying 2 V between two facing electrodes.

2D photonic crystal protein hydrogel coulometer for sensing serum albumin ligand binding.

Bovine and human serum albumin (BSA and HSA) are globular proteins that function as bloodstream carriers of hydrophobes such as fatty acids and drugs. We fabricated novel photonic crystal protein hydrogels by attaching 2D colloidal arrays onto pure BSA and HSA hydrogels. The wavelengths of the diffracted light sensitively report on the protein hydrogel surface area. The binding of charged species to the protein hydrogel gives rise to Donnan potentials that change the hydrogel volume causing shifts in the diffraction. These photonic crystal protein hydrogels act as sensitive Coulometers that monitor the hydrogel charge state. We find multiple high-affinity BSA and HSA binding sites for salicylate, ibuprofen and picosulfate by using these sensors to monitor binding of charged drugs. We demonstrate proof-of-concept for utilizing protein hydrogel sensors to monitor protein-ionic species binding.

Robust Mechanochromic Elastic One‐Dimensional Photonic Hydrogels for Touch Sensing and Flexible Displays

Mechanochromic materials which control their color variation by straightforward effective mechanical stimuli are useful for applications including switches, display devices, and sensors. It is still challenging to create mechnochromic materials with wide‐range color tunability, fast response, and sensitivity to pressure <10 kPa. Here a facile strategy to fabricate very sensitive and reversibly mechanochromic elastic photonic hydrogels (EPHs) is demonstrated. The hydrogels exhibit reversible full‐color variation within 1 s under each compression–decompression cycle. Importantly, EPH films display versatile touch‐induced chromatic behavior even under forces below 0.5 N or pressures down to 1 kPa. Furthermore, rewritable displays on EPH films are realized by the exertion of forces without any external inks. This work may provide a new way to develop smart skin materials with integrated functions of tactile sensing and color variation, as well as touch‐based flexible displays.

A 2-D photonic crystal hydrogel for selective sensing of glucose

A novel 2-D photonic crystal hydrogel for selective glucose sensing is produced by attaching a 2-D colloidal array onto the phenylboronic acid modified hydrogel.

双单体分子印迹光子晶体凝胶膜检测双酚A

The molecularly imprinted photonic hydrogels(MIPH),based on the combination of photonic crystal and molecular imprinting technique,was prepared with Bisphenol A as template molecules,methanol as solvent,methacrylate and acrylamide as double functional monomer,ethylene glycol dimethyl methacrylate as cross-linked,2,2-diethoxyacetophenone as photoinitiator.When the molecular imprint photonic crystal film is soaked in bisphenol A buffer solution,peak wavelengths of Bragg diffraction will red-shift 36 nm with the concentration increasing from 10- 10mol/L to 10- 3mol/L.The color changes can be distinguished by bare eye.More importantly,the color changing is not influenced by the ionic strength and other structure analogue molecules like ferulic acid,salicylic acid and hydroquinol.

Responsive Photonic Hydrogels Based on Nanocrystalline Cellulose

Responsive Photonic Hydrogels Based on Nanocrystalline Cellulose

Responsive Photonic Hydrogels Based on Nanocrystalline Cellulose

Alles in Ordnung: Die Selbstorganisation von nanokristalliner Cellulose (NCC) mit Hydrogelmonomeren ergibt Nanokomposite mit chiral-nematischer Fernordnung. Die Kombination der chiralen Struktur mit dem Quellverhalten von Hydrogelen resultiert in einem Schillern, das durch verschiedene Reize kontrolliert werden kann. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Molecular imprinted photonic crystal hydrogels for the rapid and label-free detection of imidacloprid

A novel sensor for the rapid and label-free detection of imidacloprid was developed based on the combination of a colloidal crystal templating method and a molecular imprinting technique. The molecular imprinted photonic hydrogel film was prepared with methacrylic acid as monomers, ethylene glycol dimethylacrylate as cross-linkers and imidacloprid as imprinting template molecules. When the colloidal crystal template and the molecularly imprinted template was removed, the resulted MIPH film possessed a highly ordered three-dimensional macroporous structure with nanocavities. The response of the MIPH film to imidacloprid in aqueous solution can be detected through a readable Bragg diffraction red shift. When the concentration of imidacloprid increased from 10−13 to 10−7g/mL, the Bragg diffraction peak shifted from 551 to 589nm, while there were no obvious peak shifts for thiamethoxam and acetamiprid. This sensor which comprises of no label techniques and expensive instruments has potential application for the detection of trace imidacloprid.

In vivo imaging of the morphology and changes in pH along the gastrointestinal tract of Japanese medaka by photonic band-gap hydrogel microspheres

Colloidal crystalline microspheres with photonic band-gap properties responsive to media pH have been developed for in vivo imaging purposes. These colloidal crystalline microspheres were constructed from monodispersed core–shell nano-size particles with poly(styrene-co-acrylic acid) (PS-co-PAA) cores and poly(acrylic acid-co-N-isopropylacrylamide) (PAA-co-PNIPAM) hydrogel shells cross-linked by N,N′-methylenebisacrylamide. A significant shift in the photonic band-gap properties of these colloidal crystalline microspheres was observed in the pH range of 4–5. This was caused by the discontinuous volume phase transition of the hydrogel coating, due to the protonation/deprotonation of its acrylic acid moieties, on the core–shell nano-sized particles within the microspheres. The in vivo imaging capability of these pH-responsive photonic microspheres was demonstrated on a test organism – Japanese medaka, Oryzia latipes – in which the morphology and change in pH along their gastrointestinal (GI) tracts were revealed under an ordinary optical microscope. This work illustrates the potential of stimuli-responsive photonic band-gap materials in tissue-/organ-level in vivo bio-imaging.

Molecularly imprinted photonic hydrogels for fast screening of atropine in biological samples with high sensitivity

Based on molecularly imprinted photonic hydrogels (MIPHs) that combined the colloidal-crystal with molecular imprinting technique, a novel label-free colorimetric chemosensor for convenient and fast efficient detection of atropine with high sensitivity and specificity was developed. Due to the special inverse opal arrays with a thin polymer wall in which the imprinted nanocavities of atropine moleculars distributed, the proposed MIPHs designed as water-compatible exhibited high sensitive (as low as 1pg/mL), rapid responsive (less than 30s) and specific detection of atropine in complex matrix. The unique three-dimensional, highly-ordered photonic hydrogels would be obviously swelling in response to the specific atropine molecular recognition process and the response would be directly transferred into visually perceptible optical signal (change in color) that could be detected by the naked eye through Bragg diffractive shifts of ordered macroporous arrays. With a broad concentration range varying from 1pg/mL to 1μg/mL of atropine, the distinct color changes of MIPHs almost covered the whole visible-light wavelength range from blue to red for semi-quantitative analysis. The smart chemosensor was successfully employed to determine the trace level atropine in human urine samples, providing a fast and effective alternative for semi-quantitative detection of atropine for clinical analysis and forensic investigations.

Fast screening of ketamine in biological samples based on molecularly imprinted photonic hydrogels

A novel label-free colorimetric chemosensor was developed for handy and fast screening of ketamine with high sensitivity and specificity based on molecularly imprinted photonic hydrogels (MIPHs) that combined the colloidal-crystal with molecular imprinting technique. The unique inverse opal arrays with a thin polymer wall in which the imprinted nanocavities of ketamine moleculars distributed allowed high sensitive, quick responsive, specific detection of the target analyte, and good regenerating ability in an aqueous environment. Due to the hierarchical inverse opal structural characteristics, the specific ketamine molecular recognition process can induce obvious swelling of the MIPHs to be directly transferred into visually perceptible optical signal (change in color) which can be detected by the naked eye through Bragg diffractive shifts of ordered macroporous arrays. In order to enhance the recognition ability in aqueous environments, the MIPHs were designed as water-compatible and synthesized in a water–methanol system. The molecular recognition mechanisms were investigated. The proposed MIPHs were successfully employed to screen trace level ketamine in human urine and saliva samples, exhibiting high sensitivity, rapid response, and specificity in the complex matrix. The smart chemosensor can provide an effective alternative for fast screening of ketamine on the spot for forensic investigations.

Wettability gradient colorimetric sensing by amphiphilic molecular response

Herein we present a highly sensitive sensing method combining amphiphilic molecules and wettability gradient photonic hydrogels for molecular recognition and chemical sensing applications. These wettability gradient photonic films exhibit low analyte amount, fast response, as well as interference resistance, which enable them for applications in forgery detection and visual determination of analyte concentrations.

Full-color CO2 gas sensing by an inverse opal photonic hydrogel

CO2 gas sensing is of great importance because of the impact of CO2 on global climate change. Here, utilizing an inverse opal hydrogel, we describe a CO2 gas sensing method that allows highly sensitive and selective detection over a wide concentration range. The CO2 sensor is specific, quantitative, interference tolerant and without the need for special instruments.

Molecularly Imprinted Photonic Hydrogels as Colorimetric Sensors for Rapid and Label-free Detection of Vanillin

A novel colorimetric sensor for the rapid and label-free detection of vanillin, based on the combination of photonic crystal and molecular imprinting technique, was developed. The sensing platform of molecularly imprinted photonic hydrogel (MIPH) was prepared by a noncovalent and self-assembly approach using vanillin as a template molecule. Morphology characterization by scanning electron microscope (SEM) showed that the MIPH possessed a highly ordered three-dimensional (3D) macroporous structure with nanocavities. The vanillin recognition events of the created nonocavities could be directly transferred into readable optical signals through a change in Bragg diffraction of the ordered macropores array of MIPH. The Bragg diffraction peak shifted from 451 to 486 nm when the concentration of the vanillin was increased from 10⁻¹² to 10⁻³ mol L⁻¹ within 60 s, whereas there were no obvious peak shifts for methyl and ethyl vanillin, indicating that the MIPH had high selectivity and rapid response for vanillin. The adsorption results showed that the hierarchical porous structure and homogeneous layers were formed in the MIPH with higher adsorption capacity. The application of such a label-free sensor with high selectivity, high sensitivity, high stability, and easy operation might offer a potential method for rapid real-time detection of trace vanillin.

Colorimetric photonic hydrogel aptasensor for the screening of heavy metal ions

We have developed a robust method for the visual detection of heavy metal ions (such as Hg(2+) and Pb(2+)) by using aptamer-functionalized colloidal photonic crystal hydrogel (CPCH) films. The CPCHs were derived from a colloidal crystal array of monodisperse silica nanoparticles, which were polymerized within the polyacrylamide hydrogel. The heavy metal ion-responsive aptamers were then cross-linked in the hydrogel network. During detection, the specific binding of heavy metal ions and cross-linked single-stranded aptamers in the hydrogel network caused the hydrogel to shrink, which was detected as a corresponding blue shift in the Bragg diffraction peak position of the CPCHs. The shift value could be used to estimate, quantitatively, the amount of the target ion. It was demonstrated that our CPCH aptasensor could screen a wide concentration range of heavy metal ions with high selectivity and reversibility. In addition, these aptasensors could be rehydrated from dried gels for storage and aptamer protection. It is anticipated that our technology may also be used in the screening of a broad range of metal ions in food, drugs and the environment.

Independent multifunctional detection by wettability controlled inverse opal hydrogels

Utilizing the wettability of inverse opal hydrogels, we report a new strategy to construct photonic hydrogels with multiple types of reliable signals, such as non-wetting (transparent), image contrast (weak color) with shifts of diffraction maximum (bright color), developing optical sensors for multifunctional detection.