Ink Jet Printing Technology Can Not Only Be Used To Print Paper

Ink jet printing technology is not only used to print paper, but also can build DNA arrays, 3D structures, etc., with a wide range of applications. MEMS The development of ink-jet printing technology makes it more precise and efficient.

In the early 1980s, the office was full of the noise of metal tapping ink tape and leaving characters on paper. IBM The selective typewriter clattered, the daisy wheel printer clattered, and the dot matrix printer screeched.

Now, these noises have disappeared. Although we now spend more time reading on the screen, print paper has not disappeared from the stage of history.

What is the main reason for this silence? Ink jet printer. Although laser printers undertake large-scale printing tasks in the commercial environment, inkjet printers have become the printers most of us use at home and in the office.

The print head of an inkjet printer performs an extraordinary task. Even if the resolution is only 96 In the case of dpi (dots per inch), this is very common in the early models in the 1980s, and the distance from the point center to the point center is only 260 microns. To fill a standard sheet with 2.5 More than 500000 individual ink drops need to be sprayed on letter paper with cm margin. The delivery of these tiny ink drops requires very precise control, and repeated many times at the fastest possible speed. MEMS It is very suitable for this process. MEMS is an electronic device that uses micro components.

As long as a certain substance can be encapsulated into tiny ink drops with appropriate fluid characteristics, someone will find a way to adapt ink-jet technology to this substance.

Like all micro technologies, the specifications of inkjet systems have changed dramatically over time. In the mid-1980s, a typical inkjet printhead had 12 Each nozzle can spray up to 1350 ink drops per second, thus printing 150 alphanumeric characters per second. Today, high-end inkjet print heads used in commercial printers may include 21000 Each nozzle can spray 20000 to 150000 ink drops per second. Each ink drop may be only 1.5 picolins - a millionth of a liter - about 14 microns in diameter.

The ink-jet technology used by the ink-jet printer exceeded the imagination of the inventor. In addition to ink-jet dots on paper, many other applications were found. These applications include DNA for genomics Microarray, circuit routing for printed circuit board and construction of 3D printing structure. Future applications may include personalized medicine and the development of advanced batteries.

In fact, today's search for patents containing the word "inkjet" will return more than 92000 Results. As long as a certain substance can be encapsulated into tiny ink drops with appropriate fluid characteristics, someone will find a way to adapt ink-jet technology to this substance.

How MEMS Changes Ink Jet Printing Technology

The history of inkjet technology can be traced back to 1948, when Swedish inventor Rune Elmqvist He applied for a patent for a chart recorder, which uses a very thin glass tube and leaves traces on the moving paper tape by controlling the ink flow. A few years later, he used this device to display an instrument for recording electrocardiogram.

Richard G. Sweet of Stanford University in 1965 A chart recorder is developed, which decomposes the ink flow into evenly charged ink drops. The guide electrodes on both sides of the flow can make the ink drops fall directly on the paper, or deflect them to the absorption pad or the drainage tank for collection and reuse.

This technology is called continuous inkjet printing. By 1976, IBM had applied it to the commercial printer IBM 6640 Medium. However, continuous ink-jet will waste ink due to ink evaporation even if it is recycled, which limits their attraction.

In order to solve the waste problem of continuous inkjet, others are committed to developing on-demand inkjet printers. Each orifice on the print head emits one ink drop at a time, avoiding the waste of continuous ink drops. The surface tension holds the ink in a tiny open nozzle until a mechanism pushes the ink to eject an ink drop. Each ink drop hitting the paper will form a dot, and the print head will move back and forth to generate an image. The print head with multiple orifices can spray many ink drops at the same time, so each time the print head passes the page, it will add a part of the image, not just a thin line.

In the late 1970s, Siemens took the lead in selling on-demand inkjet printers. It is not an independent device like a modern desktop printer, but a Siemens PT80i (print terminal 80 Ink jet) A component of a computer terminal. The printer uses piezoelectric actuators to surround 12 ink tubes and provide ink for 12 nozzles to jet ink drops and print 270 characters per second.

Piezoelectric parts depend on certain materials that will change shape when applying voltage, such as ceramic lead zirconate titanate (PZT). This effect occurs in MEMS Has proven useful in generating precise forces and motions from commands. If PZT The layer is bonded to the non piezoelectric material to form the so-called double piezoelectric parts, which will bend when the voltage is applied. In the piezoelectric ink jet nozzle, the bending of the dual piezoelectric devices will push the ink out of the nozzle hole.

However, in 1970, this novel printing technology The s is not as reliable as the mature percussion printer, and if the printer fails, the entire Siemens terminal will not be used, so it has not become popular.

At the same time, researchers from Hewlett Packard and Canon noticed that ink would boil and sputter when it came into contact with hot elements such as soldering iron. They decided to convert this sputter into a useful inkjet printer system. They know that resistors can be used as heating elements and can be miniaturized using the same technology as integrated circuits. In the printer they built, each ink nozzle contains a resistor instead of a piezoelectric actuator. The electric pulse heating resistor quickly boils a thin layer of ink to form a rapidly expanding bubble, which pushes ink drops out of the nozzle.

This work led to the launch of two competing thermal inkjet technologies almost simultaneously 40 years ago. (In the same year, in 1984, Epson launched an independent piezoelectric inkjet printer.)

HP ThinkJet from HP It is the first desktop inkjet printer based on thermal technology, designed to connect to personal computers for daily printing. It has a direct advantage over the recently developed laser printer: it is much cheaper. Price of HP's desktop laser printer US $3500 (equivalent to US $10500 today); HP's 2225A ThinkJet costs only $495 (equivalent to 1500 today USD). Ink jet printers also consume far less power than laser printers, and have less noise. It is undeniable that the resolution of inkjet printers is not high - in the early days, the resolution of inkjet printers was 96 dpi, while that of laser printers was 300 dpi - and slower.

However, the advantages of inkjet printers outweigh the disadvantages (with the improvement of technology, the advantages become more obvious), and inkjet printers begin to dominate the desktop and home printer markets. Today, more than 20 The annual market size of inkjet printers produced by companies exceeds 100 billion US dollars, and continues to grow at an annual rate of more than 8%.

Printing DNA microarrays using inkjet

With the maturity and growth of inkjet printer manufacturing business, some companies began to explore what other types of "ink" can be delivered by inkjet printers. One of them is Agilent Technologies, a spin off company of Hewlett Packard, focuses on life sciences and chemical analysis technology. Agilent has developed a method that can be used from four nucleic acid bases: cytosine (C), guanine (G) , adenine (A) and thymine (T). Specifically, the company combines the existing DNA chemical methods and inkjet printing technology to construct DNA on glass slides Microarrays are used for genomics work, such as measuring which genes are expressed by organisms under different conditions. Academic researchers have shared open source methods to transform existing inkjet printers into their own microarrays, although their specifications are much more expensive than commercial systems.

Ink jet printing technology can not only be used to print paper

In the stationary state [top] of the inkjet nozzle, the ink is held in place by the surface tension. In the thermal ink jet nozzle [left], the voltage pulse applied to the heating resistor causes a thin layer of ink to evaporate rapidly, producing an expanding vapor bubble [left, middle], and pushing the ink droplets out of the hole [left, bottom]. In less than one millisecond, the steam recondenses, the chamber cools and refills with ink, returning the nozzle to a still state. The piezoelectric ink jet nozzle [right] is driven by the piezoelectric bimorph. When the voltage [right, middle] is applied, the piezoelectric bimorph bends to push out the ink drops [right, bottom].

DNA microarray is composed of substrate (usually glass), which is lined with tiny areas called spots, and DNA strands are attached to these areas. Agilent in a single 2.5 cm x 7.6 A maximum of 1 million spots can be produced on a cm slide. Open source systems can place up to 10000 in a slightly smaller area. Each DNA strand consists of the sequence of bases C, G, A and T. In double chain In DNA, chains have complementary sequences, which are connected like rungs of a ladder, C is connected with G, and A is connected with T.

DNA microarray uses single strand DNA, each spot has millions of strands with a common sequence. When a sample containing complementary chains washes the spots, these chains bind to the chains anchored to the spots. The sample chain is marked with fluorescent molecules. Users can know which spots are in the sample by checking which spots are lit DNA sequence.

In Agilent's method of manufacturing microarrays, the printer scans the substrate several times, adds a base to each chain in the spot each time, and performs intermediate steps to prepare for the next scan.

Ink jet printing technology can not only be used to print paper

A custom designed DNA strand can be constructed at each point of the array using an inkjet system to create a DNA microarray. The print head transports the "ink" [left] droplets containing a modified monomer of nucleotide [G, C, A or T] to each point. In the first printing cycle, these monomers attach to the chemically treated glass surface. In the subsequent printing process, a monomer is connected at the end of each growing DNA strand. Each monomer includes a protective cap to prevent other monomers from joining. The additional process [not described here] washes out the nucleotide ink, applies catalyst to complete monomer binding, and strips off the protective cap to prepare for the next printing step.

Base addition is actually a three-step process. There is a molecular "cap" at the end of each growing chain in the microarray spot, which can prevent the disordered addition of more bases. Therefore, the first step is to remove or passivate those caps through the washing solution. The second step is similar to printing a page: for each spot on the microarray, the ink-jet printer adds a drop containing the next monomer molecule (C, G, A) to be added to the end of the chain Or T Modified version of). Each of these monomers contains a new cap, so that only one molecule can be added to each chain. Although the newly added monomer has been attached to the chain, the connection is not completely stable, so the third step is to use oxidant solution to modify the bond, and fully integrate the new monomer into the DNA structure. Rinse and repeat.

The versatility of open source inkjet builds allows researchers to quickly build prototype arrays with any sequence they want to try. New arrays can be designed, synthesized, and analyzed in one day DNA。 A group of researchers reported that using their system, the additional cycle time of each base is 10 to 20 minutes, or about 13 hours to produce a batch of arrays, each array contains about 10000 Dots containing 40 base chains. In contrast, Agilent's commercial microarrays usually have chains of up to 60 bases.

　　Agilent It also uses its inkjet system to synthesize another genomics tool, called oligonucleotide library. This process is the same as manufacturing microarrays, but finally all chains are cut from the substrate, dried and packaged together for customer use. Agilent The chain length of ink-jet printing library can reach 230 bases.

3D printing with two inkjet inks

In addition to printing two-dimensional pages and building one-dimensional molecular chains, inkjet technology has been used for many years to produce three-dimensional objects. One method is powder bed 3D A variant of printing in which an object is constructed by fusing or bonding powder layers in a desired pattern. The inkjet print head drops liquid adhesive to each layer of powder in the area where the finished 3D article will be formed.

HP Multi Jet Fusion (MJF) Series 3D The printer expands this method by depositing two types of ink: one is adhesive accelerator, the other is refiner, which is applied to the edge of the pattern to prevent the accelerator from penetrating into the surrounding powder. The print head with a large number of inkjet nozzles dispenses these inks, followed by an illumination strip that rapidly heats the powder and fuses it in the area where adhesive promoter is present. The fresh powder layer is then laid on top and the process is repeated until the construction is complete. MJF The printer can quickly create complex 3D objects, including objects with subtle features and internal structure.

The future of inkjet printing technology is full of hope. Researchers are exploring the possibility of using inkjet printers to manufacture various new materials and products, including biomaterials for tissue engineering, conductive materials for electronic devices, and new electrodes for batteries.

The future of inkjet printing is not just paper. This technology has completely changed the way we print, and it may also change the way we make various things.