Rewritable Data Research Articles

A rapid response photochromic diarylethene material for rewritable holographic data storage

A novel diarylethene, namely 4,5-(2,5-dimethyl thiophene) phthalimide, was synthesized and successfully introduced to rewritable holographic data storage. Upon the alternative illumination of UV and visible light (λ>400 nm), this compound underwent rapid, reversible inter-conversion between colorless open-ring isomer and yellow-green ring-closed form in both solution and polymethyl methacrylate (PMMA) film. Subsequently, we investigated the characteristics of volume homographic recording of the diarylethene-doped PMMA film (1 μm thick). The maximum refractive index modulation (0.87‰) of the film during recording could be reached within just 120 s which gave the ability of fast recording. The high quality reconstruction after 50 write/erase cycles demonstrated its excellent fatigue-resistance and high resolution. All those results indicated that this molecule was a reliable fast write/erase holographic storage material.

Rewritable digital data storage in live cells via engineered control of recombination directionality

The use of synthetic biological systems in research, healthcare, and manufacturing often requires autonomous history-dependent behavior and therefore some form of engineered biological memory. For example, the study or reprogramming of aging, cancer, or development would benefit from genetically encoded counters capable of recording up to several hundred cell division or differentiation events. Although genetic material itself provides a natural data storage medium, tools that allow researchers to reliably and reversibly write information to DNA in vivo are lacking. Here, we demonstrate a rewriteable recombinase addressable data (RAD) module that reliably stores digital information within a chromosome. RAD modules use serine integrase and excisionase functions adapted from bacteriophage to invert and restore specific DNA sequences. Our core RAD memory element is capable of passive information storage in the absence of heterologous gene expression for over 100 cell divisions and can be switched repeatedly without performance degradation, as is required to support combinatorial data storage. We also demonstrate how programmed stochasticity in RAD system performance arising from bidirectional recombination can be achieved and tuned by varying the synthesis and degradation rates of recombinase proteins. The serine recombinase functions used here do not require cell-specific cofactors and should be useful in extending computing and control methods to the study and engineering of many biological systems.

Reversible and Irreversible Laser Microinscription on Silver‐Containing Mesoporous Titania Films

Photochromic silver-containing mesoporous titania thin films are used as writable or rewritable data carriers. Continuous wave UV and visible laser radiations, respectively, can either repeatedly print and completely erase micropatterns on their surface or engrave permanent micropatterns, depending on the laser intensity.

Data storage based on photochromic and photoconvertible fluorescent proteins

The recent discovery of photoconvertible and photoswitchable fluorescent proteins (PCFPs and RSFPs, respectively) that can undergo photoinduced changes of their absorption/emission spectra opened new research possibilities in subdiffraction microscopy and optical data storage. Here we demonstrate the proof-of-principle for read only and rewritable data storage both in 2D and 3D, using PCFPs and RSFPs. The irreversible burning of information was achieved by photoconverting from green to red defined areas in a layer of the PCFP Kaede. Data were also written and erased several times in layers of the photochromic fluorescent protein Dronpa. Using IrisFP, which combines the properties of PCFPs and RSFPs, we performed the first encoding of data in four colours using only one type of fluorescent protein. Finally, three-dimensional optical data storage was demonstrated using three mutants of EosFP (d1EosFP, mEosFP and IrisFP) in their crystalline form. Two-photon excitation allowed the precise addressing of regions of interest (ROIs) within the three-dimensional crystalline matrix without excitation of out-of-focus optical planes. Hence, this contribution highlights several data storage schemes based on the remarkable properties of PCFPs/RSFPs.

Local structure of liquid Ge1Sb2Te4 for rewritable data storage use

Phase-change materials based on chalcogenide alloys have been widely used for optical datastorage and are promising materials for nonvolatile electrical memory use. However, themechanism behind the utilization is unclear as yet. Since the rewritable data storageinvolved an extremely fast laser melt-quenched process for chalcogenide alloys, theliquid structure of which is one key to investigating the mechanism of the fastreversible phase transition and hence rewritable data storage, here by meansof ab initio molecular dynamics we have studied the local structure of liquidGe1Sb2Te4. The results show that the liquid structure gives a picture of most Sb atomsbeing octahedrally coordinated, and the coexistence of tetrahedral and fivefoldcoordination at octahedral sites for Ge atoms, while Te atoms are essentiallyfourfold and threefold coordinated at octahedral sites, as characterized by partial paircorrelation functions and bond angle distributions. The local structure of liquidGe1Sb2Te4 generally resembles that of the crystalline form, except for the much lower coordinationnumber. It may be this unique liquid structure that results in the fast and reversible phasetransition between crystalline and amorphous states.

Applications of femtosecond laser induced self‐organized planar nanocracks inside fused silica glass

AbstractWe review our recent experimental efforts towards developing photonic and biophotonic applications of femtosecond laser induced self‐organized planar nanocracks inside fused silica glass. Our results show that sub‐diffraction limited, periodic, planar cracks can be produced, organized, erased and rewritten and basically controlled inside fused silica glass where they can be diagnosed optically using form birefringence. The high degree of control over these self‐replicated periodic structures allows us to investigate applications in micro‐ and nanofluidics, porous capillaries for biofiltering and rewritable data storage for harsh environments.

Write and erase mechanisms for bulk metallic glass

Microfeatures are imprinted on Pt57.5Cu14.7Ni5.3P22.5 bulk metallic glass (BMG) using thermoplastic forming. Subsequent erasing is carried out by annealing in the supercooled liquid region. The driving force for the erasing process is the capillary force controlled by the curvature and surface tension of the liquid-vacuum surface. Sluggish crystallization kinetics in this alloy permit experimental observation at temperatures where the viscosity is sufficiently low to completely erase small surface features on a time scale smaller than the crystallization time. The kinetics of the writing and erasing processes suggest that BMGs may offer a viable alternative rewritable high-density data storage technology.

Phase-change materials for rewriteable data storage

Phase-change materials are some of the most promising materials for data-storage applications. They are already used in rewriteable optical data storage and offer great potential as an emerging non-volatile electronic memory. This review looks at the unique property combination that characterizes phase-change materials. The crystalline state often shows an octahedral-like atomic arrangement, frequently accompanied by pronounced lattice distortions and huge vacancy concentrations. This can be attributed to the chemical bonding in phase-change alloys, which is promoted by p-orbitals. From this insight, phase-change alloys with desired properties can be designed. This is demonstrated for the optical properties of phase-change alloys, in particular the contrast between the amorphous and crystalline states. The origin of the fast crystallization kinetics is also discussed.

Selective Erasure of Holograms in Photorefractive and Photopolymer Materials for Rewritable and Secure Data Storage

A selective erasure/update method of multiplexed photorefractive and photopolymer holograms by use of the double Mach–Zehnder (DMZ) interferometric arrangement is proposed. The DMZ arrangement is used as the optical phase-control device for holographic recording/erasure/update operations, which can produce a pair of π-phase-shifted interference patterns with a simple optical setup. We intend to erase the holograms recorded in not only the inherently rewritable photorefractive crystal but also the photopolymer material generally used for the write-once (i.e., unerasable) holographic recording. It is experimentally confirmed that our method can erase the write-once type photopolymer holograms as well as the photorefractive holograms, although there will be a certain degree of restriction on the rewrite cycles limited by the monomer density, the degree of multiplexing and so on.

Unique Melting Behavior in Phase-Change Materials for Rewritable Data Storage

Ge2Sb2Te5 (GST) is a technologically very important phase-change material for rewritable optical and electrical storage because it can be switched rapidly back and forth between amorphous and crystalline states for millions of cycles by appropriate pulsed heating. However, an understanding of this complicated phenomenon has not yet been achieved. Here, by ab initio molecular dynamics, we unravel the reversible phase transition process of GST. The melting of rocksalt-structured GST is unique in that it forms two-dimensional linear or tangled clusters while keeping order in the perpendicular direction. It is this specific character that results in the fast and reversible phase transition between amorphous and crystalline and hence rewritable data storage.

Rewritable polarization-encoded multilayer data storage in 2,5-dimethyl-4-(p-nitrophenylazo)anisole doped polymer

We report a rewritable polarization-encoded multilayer data storage method with a polymer film doped with the azo dye DMNPAA (2,5-dimethyl-4-(p-nitrophenylazo)anisole). It is found that under two-photon excitation by a linearly polarized femtosecond laser beam at wavelength 780 nm the optical axis of DMNPAA molecules can be oriented to the perpendicular direction of the beam via a trans-cis-trans isomerization process. As a result, multilayer polarization-encoded optical data storage is demonstrated by recording two letters of a bit spacing of 4 microm in the same region of a given layer. It is shown that erasing and rewriting a particular layer is possible.

Nanoscale Ferroelectric Information Storage Based on Scanning Nonlinear Dielectric Microscopy

An investigation of ultrahigh-density ferroelectric data storage based on scanning nonlinear dielectric microscopy (SNDM) is described. For the purpose of obtaining fundamental knowledge on high-density ferroelectric data storage, several experiments on nanodomain formation in a lithium tantalate (LiTaO3) single crystal were conducted. Through domain engineering, a domain dot array with an areal density of 1.5 Tbit/inch2 was formed on congruent LiTaO3 (CLT). Sub-nanosecond (500 psec) domain switching speed also has been achieved. Next, actual information storage is demonstrated at a density of 1 Tbit/inch2. Finally, it is described that application of a very small dc offset voltage is very effective in accelerating the domain switching speed and in stabilizing the reversed nano-domain dots. Applying this offset application technique, we formed a smallest artificial nano-domain single dot of 5.1 nm in diameter and artificial nano-domain dot-array with a memory density of 10.1 Tbit/inch2 and a bit spacing of 8.0 nm, representing the highest memory density for rewritable data storage reported to date.

Nanodomain manipulation for ultrahigh density ferroelectric data storage

Nanosized inverted domain dots in ferroelectric materials have potential application inultrahigh density rewritable data storage systems. Herein, a data storage system ispresented based on scanning non-linear dielectric microscopy and a thin film offerroelectric single-crystal lithium tantalite. Through domain engineering, wesucceeded in forming our smallest artificial nanodomain single dot at 5.1 nmdiameter and an artificial nanodomain dot array with a memory density of10.1 Tbit inch−2 and a bit spacing of 8.0 nm, representing the highest memory density for rewritabledata storage reported to date. Subnanosecond (500 ps) domain switching speedhas also been achieved. Next, actual information storage with a low biterror and high memory density was performed. A bit error ratio of less than1 × 10−4 was achieved atan areal density of 258 Gbit inch−2. Moreover, actual information storage is demonstrated at a density of1 Tbit inch−2.

Realization of 10Tbit∕in.2 memory density and subnanosecond domain switching time in ferroelectric data storage

Nanosized inverted domain dots in ferroelectric materials have potential application in ultrahigh-density rewritable data storage systems. Herein, a data storage system is presented based on scanning nonlinear dielectric microscopy and a thin film of ferroelectric single-crystal lithium tantalite. Through domain engineering, nanosized inverted domain dots have been successfully formed at a data density above 10.1Tbit∕in.2 and subnanosecond (500ps) domain switching speed has been achieved. Moreover, actual information storage is demonstrated at a density of 1Tbit∕in.2

Optical Properties of Electron Beam Evaporated Ge2Sb2Te5 Thin Films for Rewritable High Density Data Storage Applications

Ge 2 Sb 2 Te 5 thin films were deposited by electron beam evaporation onto glass substrates at 303 K and 453 K substrate temperatures. The effect of film microstructure (modified by substrate temperature) on optical properties over the visible region was analyzed. It is observed that Ge 2 Sb2Te 5 thin films show good optical contrast in the lower wavelength region. Microstructural and spectral dependence on optical constants (n & k) of the films were studied. The optical band gap and the nature of transition of the Ge 2 Sb 2 Te 5 thin films also have been reported. Amorphous to crystalline microstructural phase change due to substrate temperature in these films was confirmed by X-ray diffraction and SEM analysis.

Photochromic diarylethene for rewritable holographic data storage

A new diarylethene doped with poly(methyl methacrylate) film is developed and its characteristics of volume holographic recording are investigated. The maximum diffraction efficiency of the 10microm thick film is 1.2%, and the rewritable hologram recording exhibits its high resolution, fatigue resistance, negligible shrinkage, and long lifetime, which are critical to apply this material to high-density rewritable holographic data storage.

10 Tbit/inch2 Ferroelectric Data Storage with Offset Voltage Application Method

AbstractFerroelectrics are expected to become one of the next generation ultra-high density data storage media. The requirements for pulse amplitude and the duration to switch the domain were both markedly decreased by using a new domain stabilizing method; offset voltage application method. Additionally, with this method it became possible to invert a smaller domain with a diameter of less than 10 nm. Finally, significant progress was made regarding the memory density for ferroelectric data storage, and an area density of 10.1 Tera-bit/inch2 was successfully achieved. This represents the highest memory density for rewritable data storage reported to date.

On the crystallization of thin films composed of Sb3.6Te with Ge for rewritable data storage

This article addresses the crystallization of amorphous Sb3.6Te films (40 nm thick) and 5 at. % Ge containing Sb3.6Te films (10, 20, and 40 nm thick) as studied with transmission electron microcopy using in situ annealing. These materials exhibit growth-dominated crystallization, in contrast to the usual Ge2Sb2Te5 that shows nucleation-dominated crystallization. Particularly the crystal-growth velocity in these systems has been measured as a function of temperature from which the activation energy for growth can be derived. The strong effect of the 5 at. % Ge addition on the total crystallization behavior is revealed by the following four phenomena: Ge increases the crystallization temperature (from 95 to 150 °C), increases the activation energy for growth (from 1.58 to 2.37 eV), increases the nucleation rate and decreases the growth anisotropy. The crystallites have a special transrotational structure and a mechanism responsible for the development of this special structure is delineated.

Diarylethene Materials for Rewritable Volume Holographic DataStorage

The photochromic diarylethene,1,2-bis(2-methyl-5-(4-formylphenyl)-thien-3-yl)perfluorocyclopentene(1a) is studied and its applicable potential in rewritable volumeholographic data storage is verified. Holographic recording films of10-µm thickness have been fabricated. The refractive index modulation(Δn = 1.15×10-3) between the open- and close-ring formsis detected to be large enough so that the films are suitable for theproduction of volume holographic storage. The experiments of anglemultiplexing and rewriting holograms show that the materials are fitfor volume holographic data storage.

Tbit/Inch 2 Data Storage Using Scanning Nonlinear Dielectric Microscopy

Nano-sized inverted domain dots in ferroelectric materials is a technology with potential applications in ultrahigh-density rewritable data storage systems. Up to now, we have studied domain inversion characteristics of stoichiometric and congruent LiTaO 3 single crystals in nanoscopic area using scanning nonlinear dielectric microscopy (SNDM), which is the technique for observing ferroelectric polarization distribution with sub-nanometer resolution. In this study, we have revealed nano-sized inverted domain remained stably for a long time, and successfully formed inverted domain dots at a data density of 1.50 Tbit/inch 2, representing the highest memory density for rewritable electric data storage reported to date.