Molecular memory
Encyclopedia
Molecular memory is a term for data storage
technologies that use molecular species as the data storage element, rather than e.g. circuits
, magnetics, inorganic materials or physical shapes. The molecular component can be described as a molecular switch
, and may perform this function by any of several mechanisms, including charge
storage, photochromism
, or changes in capacitance
. In a perfect molecular memory device, each individual molecule contains a bit
of data, leading to massive data capacity. However, practical devices are more likely to use large numbers of molecules for each bit, in the manner of 3D optical data storage
(many examples of which can be considered molecular memory devices). The term "molecular memory" is most often used to mean indicate very fast, electronically addressed solid-state data storage, as is the term computer memory
. At present, molecular memories are still found only in laboratories.
-based polymer
s which are capable of storing electric charge
. Once a certain voltage threshold is achieved the material oxidizes, releasing an electric charge. The process is reversible, in effect creating an electric capacitor
. The properties of the material allow for a much greater capacitance per unit area than with conventional DRAM memory, thus potentially leading to smaller and cheaper integrated circuit
s.
Several universities and a number of companies (Hewlett Packard, ZettaCore) have announced work on molecular memories, which some hope will supplant DRAM
memory as the lowest cost technology for high-speed computer memory
. NASA
is also supporting research on non-volatile
molecular memories.
Data storage device
thumb|200px|right|A reel-to-reel tape recorder .The magnetic tape is a data storage medium. The recorder is data storage equipment using a portable medium to store the data....
technologies that use molecular species as the data storage element, rather than e.g. circuits
Electronic circuit
An electronic circuit is composed of individual electronic components, such as resistors, transistors, capacitors, inductors and diodes, connected by conductive wires or traces through which electric current can flow...
, magnetics, inorganic materials or physical shapes. The molecular component can be described as a molecular switch
Molecular switch
A molecular switch is a molecule that can be reversibly shifted between two or more stable states. The molecules may be shifted between the states in response to changes in e.g. pH, light, temperature, an electrical current, microenvironment, or the presence of a ligand. In some cases, a...
, and may perform this function by any of several mechanisms, including charge
Charge (physics)
In physics, a charge may refer to one of many different quantities, such as the electric charge in electromagnetism or the color charge in quantum chromodynamics. Charges are associated with conserved quantum numbers.-Formal definition:...
storage, photochromism
Photochromism
Photochromism is the reversible transformation of a chemical species between two forms by the absorption of electromagnetic radiation, where the two forms have different absorption spectra. Trivially, this can be described as a reversible change of colour upon exposure to light...
, or changes in capacitance
Capacitance
In electromagnetism and electronics, capacitance is the ability of a capacitor to store energy in an electric field. Capacitance is also a measure of the amount of electric potential energy stored for a given electric potential. A common form of energy storage device is a parallel-plate capacitor...
. In a perfect molecular memory device, each individual molecule contains a bit
Bit
A bit is the basic unit of information in computing and telecommunications; it is the amount of information stored by a digital device or other physical system that exists in one of two possible distinct states...
of data, leading to massive data capacity. However, practical devices are more likely to use large numbers of molecules for each bit, in the manner of 3D optical data storage
3D optical data storage
3D optical data storage is the term given to any form of optical data storage in which information can be recorded and/or read with three dimensional resolution ....
(many examples of which can be considered molecular memory devices). The term "molecular memory" is most often used to mean indicate very fast, electronically addressed solid-state data storage, as is the term computer memory
Computer memory
In computing, memory refers to the physical devices used to store programs or data on a temporary or permanent basis for use in a computer or other digital electronic device. The term primary memory is used for the information in physical systems which are fast In computing, memory refers to the...
. At present, molecular memories are still found only in laboratories.
Examples
One approach to molecular memories is based on special compounds such as porphyrinPorphyrin
Porphyrins are a group of organic compounds, many naturally occurring. One of the best-known porphyrins is heme, the pigment in red blood cells; heme is a cofactor of the protein hemoglobin. Porphyrins are heterocyclic macrocycles composed of four modified pyrrole subunits interconnected at...
-based polymer
Polymer
A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...
s which are capable of storing electric charge
Electric charge
Electric charge is a physical property of matter that causes it to experience a force when near other electrically charged matter. Electric charge comes in two types, called positive and negative. Two positively charged substances, or objects, experience a mutual repulsive force, as do two...
. Once a certain voltage threshold is achieved the material oxidizes, releasing an electric charge. The process is reversible, in effect creating an electric capacitor
Capacitor
A capacitor is a passive two-terminal electrical component used to store energy in an electric field. The forms of practical capacitors vary widely, but all contain at least two electrical conductors separated by a dielectric ; for example, one common construction consists of metal foils separated...
. The properties of the material allow for a much greater capacitance per unit area than with conventional DRAM memory, thus potentially leading to smaller and cheaper integrated circuit
Integrated circuit
An integrated circuit or monolithic integrated circuit is an electronic circuit manufactured by the patterned diffusion of trace elements into the surface of a thin substrate of semiconductor material...
s.
Several universities and a number of companies (Hewlett Packard, ZettaCore) have announced work on molecular memories, which some hope will supplant DRAM
Dram
Dram or DRAM may refer to:As a unit of measure:* Dram , an imperial unit of mass and volume* Armenian dram, a monetary unit* Dirham, a unit of currency in several Arab nationsOther uses:...
memory as the lowest cost technology for high-speed computer memory
Computer memory
In computing, memory refers to the physical devices used to store programs or data on a temporary or permanent basis for use in a computer or other digital electronic device. The term primary memory is used for the information in physical systems which are fast In computing, memory refers to the...
. NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
is also supporting research on non-volatile
Non-volatile memory
Non-volatile memory, nonvolatile memory, NVM or non-volatile storage, in the most basic sense, is computer memory that can retain the stored information even when not powered. Examples of non-volatile memory include read-only memory, flash memory, ferroelectric RAM, most types of magnetic computer...
molecular memories.