In previous works, we have used two-photon induced photochemistry to fabricate 3D microstructures based on proteins, anti-bodies, and enzymes for different types of bio-applications. Among them, we can cite collagen lines to guide the movement of living cells, peptide modified GFP biosensing pads to detect Gram positive bacteria, anti-body pads to determine the type of red blood cells, and trypsin columns in a microfluidic channel to obtain a real time biochemical micro-reactor. In this paper, we report for the first time on two-photon 3D microfabrication of DNA material. We also present our preliminary results on using a commercial 3D printer based on a video projector to polymerize slicing layers of gelatine-objects.
Natural macromolecules are very promising row materials to be used in modern technology including security and defense. They are abundant in nature, easy to extract and possess biocompatibility and biodegradability properties. These materials can be modified throughout chemical or physical processes, and can be doped with lithium and rare earth salts, ionic liquids, organic and inorganic acids. In this communication samples of DNA and modified DNA were doped with Prussian Blue (PB), poly(ethylene dioxythiophene) (PEDOT), europium and erbium triflate and organic dyes such as Nile Blue (NB), Disperse Red 1 (DR1) and Disperse Orange 3 (DO3). The colored or colorless membranes were characterized by electrochemical and spectroscopic measurements, and they were applied in electrochromic devices (ECDs) and dye sensitized solar cells (DSSC). ECDs change the color under applied potential, so they can modulate the intensity of transmitted light of 15 to 35%. As the electrochromic materials, WO3 or Prussian blue (PB), are usually blue colored, the color change is from transparent to blue. DNA, and the complexes: DNA-CTMA, DNA-DODA and DNAPEDOT: PSS were also investigated as either hole carrier material (HTM) or polymer electrolyte in dye-sensitized solar cells (DSSC). The DNA-based samples as HTM in small DSSCs revealed a solar energy conversion efficiency of 0.56%. Polymer electrolytes of DNA-CTMA and DNA-DODA, both with 10 wt% of LiI/I2, applied in small DSSC, exhibited the efficiencies of 0.18 and 0.66%, respectively. The obtained results show that natural macromolecules-based membranes are not only environmentally friendly but are also promising materials to be investigated for several electrochemical devices. However, to obtain better performances more research is still needed.
This paper is a review of the recent research in bio-based materials for photonics and electronics applications. Materials
that we have been working with include: deoxyribonucleic acid (DNA)-based biopolymers and nucleobases. We will
highlight work on increasing the ionic conductivity of DNA-based membranes, enhancing the direct (DC) current and
photoconductivity of DNA-based biopolymers, crosslinking of DNA-based biopolymers and promising applications for
Digital Colour Management System (DCMS) and its application to new adaptive camouflage system are presented in this paper. The DCMS is a digital colour rendering method which would allow for transformation of a real image into a set of colour pixels displayed on a computer monitor. Consequently, it can analyse pixels’ colour which comprise images of the environment such as desert, semi-desert, jungle, farmland or rocky mountain in order to prepare an adaptive camouflage pattern most suited for the terrain. This system is described in present work as well as the use the subtractive colours mixing method to construct the real time colour changing electrochromic window/pixel (ECD) for camouflage purpose. The ECD with glass/ITO/Prussian Blue(PB)/electrolyte/CeO2-TiO2/ITO/glass configuration was assembled and characterized. The ECD switched between green and yellow after ±1.5 V application and the colours have been controlled by Digital Colour Management System and described by CIE LAB parameters.
Functionalization of deoxyribonucleic acid (DNA) with surfactants, photosensitive and conductivity increasing molecules as well as thin film processing is reviewed and discussed. The comparative spectroscopic studies of chemical and photothermal stability of several chromophores show a better stability in DNA-cetyltrimethylammonium (CTMA) surfactant complexes than in polycarbonate (PC) or poly(ethylene glycol) (PEG) matrices. Also the optical damage threshold in nanosecond pulsed laser illumination is higher in thin films of bio-macromolecules such as DNA, DNACTMA, collagen than in PC. The electrical conductivity of doped DNA based systems exhibits a typical ionic character and can be improved by an appropriate doping. Practical applications of DNA based complexes are reviewed and discussed.
Gelatin and DNA are abundant natural products with very good biodegradation properties and can be used to obtain
acetic acid or LiClO4-based gel polymer electrolytes (GPEs) with high ionic conductivity and good stability. This article
presents the results of the ionic conductivity measurements of GPEs membranes based on crosslinked and plasticized
gelatin and on plasticized DNA as well as on inserted/extracted charge density of electrochemical devices (ECDs)
obtained with these samples. The membranes were analyzed by impedance spectroscopy, UV-Vis spectroscopy and the
ECDs by charge density measurements, respectively. At room temperature the measured ionic conductivity of the
membranes is in the range of 10-4-10-5 S/cm. It obeys predominantly an Arrhenius relationship in function of
temperature. The ECD with red gelatin changed the color from red to deep red and the ECD with DNA-based electrolyte
changes from transparent to blue. The inserted charge density values of these ECDs were of -3.0 mC/cm2 for the device
with red gelatin and -6.6 mC/cm2 for the ECD with DNA-based electrolyte. The reverse potential application promoted a
charge extraction and, as consequence, bleaching of the devices. Good ionic conductivity results combined with
transparency and good adhesion to the electrodes and promising preliminary results of small ECDs have shown that
gelatin and DNA-based GPEs are very promising materials to be used as gel polymer electrolytes in electrochromic
Polysaccharides like starch and cellulose derivatives, hydroxyethylcellulose (HEC) or hydroxypropylcellulose (HPC) were modified to obtain solid polymeric electrolytes. The chemical modifications were performed by the grafting of polymers with poly(ethylene oxide) mono and diisocyanates or JEFFAMINE (Shiff base). The physical modifications were made by the plasticization process of starch and cellulose derivatives with glycerol and ethylene glycol. All the samples obtained from polysaccharides were characterized by X-ray, thermal analysis (DSC) and impedance spectroscopy. The plasticized samples showed low glass transition temperatures (Tg); for HEC the value was about -60°C and for starch it was about -30°C. Tg values for grafted samples were of about -58°C for starch and -7°C for HPC. The low Tg values obtained are important to ensure good ionic conductivity that reached the values of about 10-5 Scm-1 for plasticized samples and 10-6 Scm-1 for grafted ones at room temperature. The good film forming and ionic conductivity properties of the samples of HEC, HPC and starch are very interesting candidates to be used as solid polymer electrolytes.
Solid state electrochromic devices (ECD) are of considerable technological and commercial interest because of their controllable transmission, absorption and/or reflectance. For instance, a major application of these devices is in smart windows that can regulate the solar gains of buildings and also in glare attenuation in automobile rear view mirrors. Other applications include solar cells, small and large area flat panel displays, satellite temperature control, food monitoring, and document authentication. A typical electrochromic device has a five-layer structure: GS/TC/EC/IC/IS/TC/GS, where GS is a glass substrate, TC is a transparent conductor, generally ITO (indium tin oxide) or FTO (fluorine tin oxide), EC is an electrochromic coating, IC is an ion conductor (solid or liquid electrolyte) and IS is an ion storage coating. Generally, the EC and IS layers are deposited separately on the TC coatings and then jointed with the IC and sealed. The EC and IS are thin films that can be deposited by sputtering, CVD, sol-gel precursors, etc.
There are different kinds of organic, inorganic and organic-inorganic films that can be used to make electrochromic devices. Thin electrochromic films can be: WO3, Nb2O5, Nb2O5:Li+ or Nb2O5-TiO2 coatings, ions storage films: CeO2-TiO2, CeO2-ZrO2 or CeO2-TiO2-ZrO2 and electrolytes like Organically Modified Electrolytes (Ormolytes) or polymeric films also based on natural polymers like starch or cellulose. These last are very interesting due to their high ionic conductivity, high transparency and good mechanical properties.
This paper describes construction and properties of different thin oxide and polymeric films and also shows the optical response of an all sol-gel electrochromic device with WO3/Ormolyte/CeO2-TiO2 configuration.
An electrochromic material (EC) reversibly changes its optical characteristics response, coloring and bleaching states when a small voltage or current is passed through it. This phenomenon is used to develop electrochromic devices like smart windows, which control the amount of heat and light entering in a building and optimize energy consumption. The change of the transparency of these devices involves the injection and extraction of small cations and electrons into the EC material and study of the kinetics of ions injection implies on operation understanding of these devices.
Pure and doped niobium oxides (Nb2O5) are promising cathodic electrochromic materials and their electrooptical
performance depends strongly of its structural morphology. The sol-gel process allows for facile fabrication of large area coatings at a low cost and offers advantages of controlling the composition and microstructure of the films. In order to study the solid sate diffusion of lithium into Nb2O5, Nb2O5:Li+ and Nb2O5:WO3, two electroanalytical
techniques have been used i.e. galvanostatic intermittent titration technique (GITT) and electrochemical impedance spectroscopy (EIS). GITT have been applied in order to obtain the chemical diffusion coefficient of Lix in Nb2O5 doped and undoped films, where the values approaching were of the 2.5x10-11 cm2s-1 at x=0,83, 7.4x10-13 cm2s-1 at x=1.65 and 1.6x10-10 cm2s-1 at x=0.33 for Nb2O5, Nb2O5:Li+ and Nb2O5-WO3 respectively. From these measurements it was also observed that within each film, D increases as x increases.
Thin films of CeO2-TiO2-ZrO2 with 23 percent mol of Ce, 45 percent mol of Ti and 32 percent mol of Zr have been prepared by the sol-gel method. The precursor sol was synthesized from a mixture of Ce(NH4)2 (NO3)6, Ti(OPi)4 and Zr(OPi)4 solubilized in isopropanol and then sonicated. Xerogels were characterized by thermal analysis and x-ray diffraction. The films were deposited by dip-coating technique on ITO-Asahi glass and tread at 80 degrees C during 15 min and 450 degrees C during 15 min in oxygen atmosphere. Through the addition of lithium salt to the precursor solution films with different electrochemical performance are obtained. Their possible use as ion storage in electro chromic devices was analyzed by spectroelectrochemical measurements using cyclic voltammetry and chronoamperometry coupled to spectrometric measurement.