Micro-Inkjet Printer Head

Presented on April, 2009

One of the highly demanding products from MEMS application is Ink jet printer head which is core part of ink jet printer. In inkjet printer, ink is emitted from a series of nozzles in a print head, spraying drops of ink directly on the paper as the nozzles pass over a variety of possible media, i.e. paper or other specialised materials. The liquid ink in various colours is squirted at the paper to build up an image.

Role of Print Head

• The print head of the inkjet printer scans the page in horizontal strips, using a motor to move it back and forth, as another motor rolls the paper in vertical steps.
• A strip of the image is printed, then the paper moves on, ready for the next strip.
• To speed things up, the print head doesn’t print just a single row of picture elements or ‘pixels’ in each pass, but a vertical row of pixels at a time.
• Most inkjets use thermal technology, whereby heat is used to fire ink onto the paper.
• There are three main stages with this method.

1.The squirt is initiated by heating the ink to create a bubble until the pressure forces it to burst and hit the paper.

2.The bubble then collapses as the element cools, and the resulting vacuum draws ink from the reservoir to replace the ink that was ejected, as illustrated below.

3.The use of heat in thermal printers creates a need for a cooling process as well, which adds time to the printing process.

• Thermal inkjet print heads contain between 300 and 600 nozzles in total, each about the diameter of a human hair (approx. 70 microns).
• These deliver drops which contain around 8 – 10 picolitres (a million millionth of a litre), creating dot sizes of between 50 and 60 microns in diameter.
• Cyan, magenta and yellow inks are normally delivered via a combined print-head.
• Several small colour ink drops – typically between four and eight – can be combined to form dots of variable size, which gives inkjets a bigger palette of colours and smoother images.
• Inkjet printing mechanisms can be categorized as either continuous inkjet or drop-on-demand inkjet. Drop-on-demand inkjet printers selectively eject droplets of ink toward a printing media to create an image.
• Such printers typically include a print head having an array of nozzles, each of which is supplied with ink.
• Each of the nozzles communicates with a chamber which can be pressurized in response to an electrical impulse to induce the generation of an ink droplet from the outlet of the nozzle.
• Many such printers use piezoelectric transducers to create the momentary pressure necessary to generate an ink droplet.
• Such piezoelectric transducers are capable of generating the momentary pressures necessary for useful drop-on-demand printing but they are relatively difficult and expensive to manufacture since the piezoelectric crystals (which are formed from a brittle, ceramic material) must be micro-machined and precision installed behind the very small ink chambers connected to each of the inkjet nozzles of the printer.
• Additionally, piezoelectric transducers require relatively high voltage, high power electrical pulses to effectively drive them in such printers.
  • To overcome these shortcomings, drop-on-demand printers utilizing thermally-actuated paddles have been suggested.
    • Each paddle would include two dissimilar metals and a heating element connected thereto. •When an electrical pulse is conducted to the heating element, the difference in the coefficient of expansion between the two dissimilar metals causes them to momentarily curl in much the same action as a bimetallic thermometer, only much quicker.
    • A paddle is attached to the dissimilar metals to convert momentary curling action of these metals into a compressive wave which effectively ejects a droplet of ink out of the nozzle outlet.

PRESENT INVENTION

• According to a feature of the present invention, a drop-on-demand inkjet print head includes

1. a nozzle with an ink outlet,
2. an ink supply channel through which a body of ink is supplied to the nozzle, and
3. a member movable in the ink supply channel toward the nozzle outlet for causing a droplet to separate from the body of ink.

• A micro-actuator applies a mechanical force to the member.
• The micro-actuator includes a body of elastomer material having opposed first and second surfaces spaced apart in a first direction by a predetermined at-rest dimension.
• A charge mechanism is coupled to the first opposed surface of the elastomer material so as to apply an electrical charge in the first direction.
• The charge is spatially varied in a second direction substantially normal to the first direction so as to create spatially varied mechanical forces across the elastomer material such that the elastomer material exhibits spatially varied growth in the first direction.
• The member is associated with the second opposed surface of the elastomer material so as to move in the first direction in response to growth of the elastomer material.
• Epson Develops a Next-Generation Inkjet Print Head Using an Original Thin-Film Piezo Element
• The Micro Piezo print head is an inkjet print head which utilizes Epson’s original Micro Piezo technology.
• This technology uses electrical signals to change the shape of piezo elements and then fires ink droplets according to the physical force generated by the change in shape of these elements.
• Compared to other inkjet systems, Micro Piezo technology offers superior ink ejection performance, compatibility with a wide variety of inks, and durability.
• Epson is currently focusing its development efforts on creating a next-generation Micro Piezo print head to support expansion of the inkjet field beyond consumer printers and to strengthen its applications for business and industry. Through these efforts, Epson has achieved the following:

1. Created a piezo element with the world’s highest degree of distortion through film thickness reduction and materials development.
2. Raised density levels by developing and utilizing innovative thin-film processing techniques.
3. Designed a high-density ink reservoir through independent MEMS technology development.

Special characteristics of Epson’s original Micro Piezo print head

• This print head fulfills all the requirements for an inkjet print head—superior ink ejection performance, compatibility with a wide variety of inks, and durability.
• The print head also makes it possible to control not only water-based pigment ink with superior water and light resistance, but also a wide variety of ink types in miniscule quantities, and fire them with high precision.

1. Ink ejection performance

• Meniscus control, which limits vibration on the surface of the liquid in the nozzle, makes it possible to achieve improved gradation and faster print speeds in addition to the following advantages: –Perfectly spherical dots –High precision impact point control –Higher drive frequencies –Variable-sized ink droplets (MSDT: multi-sized dot technology

2. Ink compatibility

• Epson’s original pigment ink achieves high levels of color reproduction and durability. •Industrial applications such as solvent ink, color filters, and UV ink are currently under development.

3. Durability

• Because it utilizes a permanent print head, the technology is applicable to a wide range of uses ranging from consumer printers to industrial manufacturing equipment.

fig : Structure of the next-generation Micro Piezo print head

 

Nanotechnology Implementation: CNTFET

Presented on Feb 2009

Carbon nanotubes (CNTs) are nanometer-diameter carbon cylinders consisting of graphene sheet wrapped up to form tube.C-60 allotropes, also called fullerenes are used to make CNT. All carbon atoms are involved in hexagonal aromatic rings only and are therefore in equivalent position, except at the nanotube tips where 6×5 = 30 atoms at each tip are involved in pentagonal rings.

CNT has unique electrical and mechanical properties that it can be shaped to act as conductor, semiconductor and insulator depending on the armchair, chiral and zig-zag structure respectively.

It may be composed of a single shell to form single wall nanotubes (SWNTs) or of several concentric shells to form multi-wall nanotubes (MWNTs).
MWNT was discovered earlier than the latter, which is comprised of 2 to 30 concentric graphitic layers, whose diameter ranges from 10 to 50 nm and more than 10 mm in length.
SWNT, on the other hand, is a lot thinner due to its single graphite layer and has diameter from 1.0 to 1.4 nm.

Single-Walled CNT

Multi-Walled CNT

Comparision of CNT with other

Property	Carbon Nanotubes	Comparatively
Size	0.6-1.8 nm in diameter	Si wires at least 50nm thick
Strength	45 Billion Pascals	Steel alloys have 2 Billion P.
Resilience	Bent and straightened without damage	Metals fracture when bent and restraightened
Conductivity	Estimated at 109 A/cm2	Cu wires burn at 106 A/cm2
Cost	$2500/gram by BuckyUSA in Houston	Gold is $30/gram

Progress of transistor technology

CNTFET features

Main role of CNT as the conducting channel of a MOSFET.

• These new devices are very similar to the CMOS FETs.
• All CNFETs are pFETs by nature.
• nFETs can be made through
  • Annealing
  • Doping
• Very low current and power consumption
• Although tubes are 3nm thick , CNFETs are still the size of the contacts, about 20nm.

Analysis : Transfer Characteristics

•As generally CNT FETs are of p-FET, so the origin of the holes is an important question to address.

•One possibility is that the carrier concentration is inherent to the NT.

•Another possibility is that the majority of carriers are injected at the gold–nanotube contacts. The higher work function of gold leads to the generation of holes in the NT by electron transfer from the NT to the gold electrodes.

Challenges

• CNTs are flexible tubes that can be made conducting or semiconducting.
• Nano-scale, strong and flexible.

Main Challenges are:

• Multilevel interconnects not available
• Chip density still limited to the density of contacts.
• Tube density not entirely exploited
• Fabrication is still a stochastic process
• Alternatives to gold contacts need to be found.

Advantages of CNT FET as Memory

• Great potential for storage memory (116 Gb/cm2 )
• Small size offers faster switching speeds (100GHz ) and low power
• Easy to fabricate: standard semiconductor process
• Bistability gives well defined on & off states
• Nonvolatile nature: no need to refresh.
• Faster than SRAM, denser than DRAM, cheaper than flash memory.
• Have an almost unlimited life, resistant to radiation and magnetism—better than hard drive.

Conclusions

• CMOS technology is approaching saturation – problems in the nanometer range
• Carbon nanotube based FET is one of the best alternative for CMOS technology.

References

• P. Avouris, J, Appenzeller, R.

Martel, And S. Wind, “Carbon nanotube electronics,” P. IEEE, vol. 91, no. 11, pp. 1772-1784, Nov.2003.

• A. Graham, G. Duesberg, W. Hoenlein, F. Kreupl, M. Liebau, R. Martin, B. Rajsekharan, W. Pamler, R. Seidal, W. Steinhoegl, and E. Unger, “ How do carbon nanotubes fit into the semiconductor roadmap?,” Appl.Phys. A, vol. 80, no. 6, pp. 1141-1151, 2005.

• M.P. Anantram and F. Leonard, “Physics of carbon nanotube electronic devices,” Rep. Prog. Phys., vol. 69, no. 3, pp. 507-561, 2006.

•J. B. Cui, et al. “Carbon nanotube memory devices of high charge storage stability”, 2002 Appl. Phys. Lett.

•http://www.photon.t.u-tokyo.ac.jp/~maruyama/agallery/nanotubes

•“Helical microtubules of graphitic carbon”, S. Iijima, Nature 354, 56 (1991)

•http://www.wikipedia.com

•Physics – Springer Handbook of NanoTechnology – B. Bhushan (2003) WW

 

Nano Machines – promising products of Nanotechnology

Nano Machines are devices which has the property of self replications and self reassembly that is actually built from individual atoms. In the fields of Nanomachine technology, ultimate goal is to produce the Assembler which is designed to manipulate matter at the atomic level. This means that assembler will be capable of rearranging atoms from any raw materials to produce any desired products. In theory, assembler are capable of rearranging atoms of even dirts to produce potato, chair, laptops and anything else.

Another goal of nanotechnology is to embeds the property of self replication in nanomachines to produce the copies of themselves. If scientists manage to build nanomachines that can rearrange atoms, a world of exciting possibilities will open up. Especially in the fields of nanomedicine, it can provide great revolutions providing breakthrough treatments for many diseases. We can have nanomachines that can destroy targeted cells like cancerous cells providing treatments for all types of cancerous diseases. Damaged tissues and bones can be repaired using self replication phenomena and even be used to strengthen bones and muscle tissue by building molecular support structures by reassembling nearby tissue. Also we can design nanomachines that can trap viruses and destroying themselves which can be boon for patients with HIV diseases.

Nanomachines will be able to produce any desired items from any raw materials by self reassembly which can sustain the demands of burgeoning population. So, there will be no problems like starvation, no problems of clothes, houses, cars, televisions, etc. Environmental problems can also be easily tackled by releasing the swarms of nanomachines in the upper atmosphere which can destroy CFCs gases and can build up ozone gases.

Every products have pros and cons. Obviously greatest risks is associated with military application. Self replicating nanomachines designed to target and destroy organic material could be released over enemy territory reducing the population to dust within a matter of hours. Whole country can be left empty within a day by a rival country with such potential military applications.

Another serious danger of nano machines is its ability to self replicate which can make several copies of itself by rearranging the atoms of nearby matter. Even offsprings machines will be able to replicate that can leads to uncontrolled reproduction of nano machines. Furthermore, since the nanomachines are using the planet’s resources as raw material with which to replicate, the danger is that the planet could eventually be transformed into a seething mass of nanomachines.

These are all hypothetical approaches which sounds very interestings. Still we are not able to manipulate individual atoms. When technologies reaches towards extreme minituarisation and generation of the ultra-fine finishing of high quality optical components is feasible, chemists and engineers together may reach to their target for nanomachines in future if the technology is pursued with full vigor.

 

Extreme Ultraviolet Lithography

– MY B.TECH. SEMINAR (ABSTRACTS)

This paper mainly focuses on  the fundamental concepts and existing state of development of Extreme Ultra-Violet lithography (EUVL), an alternate optical approach, for sub-100-nm generations lithography process that uses extreme ultraviolet (EUV) radiation with a wavelength in the range of 10 to 14 nanometers (nm) to carry out projection imaging. Currently, and for the last several decades, optical projection lithography has been the lithographic technique from which the high-volume of integrated circuits has been manufactured. It was widely anticipated that improvements in this technology will allow it to remain the semiconductor industry’s workhouse through the 100 nm generation of devices. Extensions of optical lithography have been made possible by a continuous reduction in the operating wavelength and simultaneous increase in numerical aperture (NA). However, when the operating wavelength is reduced below 150 nm, all materials become opaque, requiring the use of reflective designs with optics using special coatings to achieve high reflectivities at the operating wavelength.  Also, National Technology Roadmap for Semiconductors (NTRS) has presented four new approaches for sub-100 nm generations lithography, called the “New Generations Lithographies” and they have demonstrated feasibility and are in various stages of subsequent research and development. EUVL is  one such technology vying to become the successor to optical lithography.

To a large degree, EUVL has been made possible by the development of advanced Mo-Si multi-layer coatings due to which optimum reflectivities are achieved. Moreover, by modifying the camera design, EUVL could meet the lithographic challenge of defining the minimum geometry Si-transistor deemed possible, at a respectable throughput.

This paper provides an overview of the capabilities of EUVL, and explains how EUVL might be implemented. The challenges that must be overcome in order for EUVL to qualify for high-volume manufacture are also discussed.

References

1. Kinoshita, Hiroo; History of extreme ultraviolet lithography, Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures Volume 23,  Issue 6,  Nov 2005 Page(s):2584 – 2588
2. Stulen, R.H.; Sweeney, D.W.; Extreme ultraviolet lithography, Quantum Electronics, IEEE Journal of Volume 35,  Issue 5,  May 1999 Page(s):694 – 699
3. Naulleau, P.; Goldberg, K.A.; Cain, J.P.; Anderson, E.H.; Dean, K.R.; Denham, P.; Hoef, B.; Jackson, K.H.; Extreme ultraviolet lithography capabilities at the advanced light source using a 0.3-NA optic, Quantum Electronics, IEEE Journal of Volume 42,  Issue 1,  Jan. 2006 Page(s):44 – 50
4. Vaidya, S.; Sweeney, D.; Stulen, R.; Attwood, D.; Extreme ultraviolet lithography for 0.1 μm devices, VLSI Technology, Systems, and Applications, 1999. International Symposium on 8-10 June 1999 Page(s):127 – 130
5. Komori, H.; Abe, T.; Suganuma, T.; Imai, Y.; Someya, H.; Hoshino, H.; Nakano, M.; Soumagne, G.; Takabayashi, Y.; Mizoguchi, H.; Endo, A.; Toyoda, K.; Horiike, Y.; Progress of a laser-produced-plasma light source for EUV lithography, Microprocesses and Nanotechnology Conference, 2003. Digest of Papers. 2003 International 29-31 Oct. 2003 Page(s):276
6. Suganuma, T.; Abe, T.; Hoshino, H.; Imai, Y.; Komori, H.; Someya, H.; Soumagne, G.; Sugimoto, Y.; Mizoguchie, H.; Endoe, A.; Laser produced plasma light source for next generation lithography, Plasma Science, 2003. ICOPS 2003. IEEE Conference Record – Abstracts. The 30th International Conference on 2-5 June 2003 Page(s):392
7. Naulleau, P.; Goldberg, K.A.; Cain, J.P.; Anderson, E.H.; Dean, K.R.; Denham, P.; Hoef, B.; Jackson, K.H.; Extreme ultraviolet lithography capabilities at the advanced light source using a 0.3-NA optic Quantum Electronics, IEEE Journal of Volume 42,  Issue 1,  Jan. 2006 Page(s):44 – 50
8. Kang and Leblebici ;‘CMOS Digital Integrated Circuits, Analysis and Design’, Chapter 2, Fabrication of MOSFETs.
9. Kevin Bonsor, “How EUVL Chipmaking Works”,  http://computer.howstuffworks.com/euvl.htm
10. http://www.intel.com/technology/architecture-silicon/silicon.htm?iid=tech_as+silicon_head
11. http://en.wikipedia.org/wiki/Extreme_ultraviolet_lithography
12. John E. Bjorkholm; “EUV Lithography-The Successor to Optical Lithography”; Intel Paper on Extreme UV LithographyPage(s) 1-8

 

My curiosity towards Nanotech

I was studying B.Tech. electronics engineering at SVNIT college which resides at Surat, Gujarat-India. During the first year of B.tech, I studied about different type of subjects related to all the branches of engineering to have fundamental understanding about all the engineering courses. During these periods we were able to acquire abundant information about latest researches in different engineering sectors.

While I reached second year in SVNIT during my B.tech programme, I started to search about technological advancements. I was so confused about recent devices, which possess much more complicated features and getting more and more miniaturized for as well as  becoming cheaper with time. I got to know that due to reduction in size of transistors, we were able to accommodate large no. of components in a given silicon substrate and thus were able to adjust more functional features and reduced the cost accordingly. Also, due to more competitions among vendors and their compulsion to sell all earlier products after the arrival of newly featured products, companies are compelled to reduce the cost of their products with minimum margin of profit.

Presently most of the technologies are based on silicon and germanium substrate. It was actually the length of gate channel that has been reduced sharply during fabrication process. According to scientists Moore, transistors size will be reduced by half for every 18 months. This means present technologies will reach to 10 nm technology by 2020 and beyond that it seems impossible to capture the market as it can be less reliable and more expensive. Devices with size less than 10 nm operate in ballistic regime which can cause huge leakage current leading to the early failure of devices after few cycles of operation. Still to reach to that level, there are lots of limitations for silicon transistors. More we get compact form of devices, more power will dissipate. This leads to tremendous amount of heat generation which can cause explosion of devices. This is one of the great challenges that present scientists are facing. One of the pragmatic example is our present days laptops which are getting heated immediately than its older version.

When I knew all sorts of limitations that can create barrier for technological advancements, I tried to  google about the alternatives that scientists have found through researches. It was CNT-carbon nanotube based FET which can be really best alternative for present days MOSFET. CNT is a narrow tube having 1 nm diameter which is having strength 1600 times than that of steel and can easily sustain large amopunt of heat generated in the system. CNT can be conductor, semiconductor or insulator depending upon its physical configurations, that is really amazing. CNT is really a boon in the fields of nanotechnology. I also started to read articles about nanotechnology. Use of silver and gold nanoparticles as sensors that can be used for medical purposes has really fascinated me. It really surprises me that how materials changes its physical and chemical properties in nanoparticles form which is totally different from their bulk properties.

I took Nano devices as my electives during 3rd year and knew about different type of nanomaterials, nanosensors, smart sensors and different examples of nano products with working phenomena. Especially in the fields of nanoelectronics, we can have large exposure to do researches to find our own innovative novel products. Large no. of researches have been proposed by different scientists from different international lab houses and still lots of opportunities to create our own innovative designs. As Nanotechnology is a promising fields with multidisciplinary subjects where we need knowledge about biology, chemistry, physics, quantum physics and soon, this provides a real opportunity to exploit all our knowledge that we have gained from school level. Because of this I got more attention towards fields of nanotechnology with full vigor and enthusiasm.

Taking care of my interest, I took “Extreme Ultraviolet Lithography” as my seminar topic that is one of the emerging topic in the fields of nano-fabrications. There are limitations of optical lenses in creating lithography patterns when we go towards lower nm technology. It has successfully replaced by the use of optical mirrors but still number of challenges like making smoothness of mirror, proper focus and soon remain to be properly adjusted. EUV lithography is supposed to be used for the technology below 14 nm. I also learned about the designing of IC layout using IC flow design tool and design architect tool of Mentor Graphics where I reached upto design of SRAM layout but couldn’t completed it properly because of lack of mentor specialized in that work.

Finally I applied to number of renowned Universities in Europe and able to grasp most of the prestigious scholarships like HSP scholarship, TSP scholarship and Erasmus Mundus scholarship. Finally  I decided to go for subjects of interests (Nanoelectronics) rather than Universities ranking and chose KU Leuven as my final destination. I would like to thank my coordinator of KU Leuven for providing me such a wonderful prestigious EU scholarship for pursuing  Master programme in KU Leuven and Chalmers University  🙂