Printed Electronics adds security to your Banknotes

Sipca, a company founded in 1927, provides secured identification, traceability and authentication solutions and services.  A core component of their security expertise is the use of security inks that protect the majority of the worlds banknotes.  I was interested to notice that earlier this year they filed a patent application combining the use of security inks with flexible printed electronics features to further enhance the security aspects of banknotes.


The patent application is WO2016037895, published on 17 March 2016, the inventors being Brahim Kerkar and Philippe Amon.

Most recent(amended) claim 1 is:

A banknote comprising: one or more security features, at least two flexible printed electronic (FPE) elements embedded in the banknote, at least one of the one or more security features and at least one of the at least two FPE elements have an interrelationship with each other, and a plurality of the at least two FPE elements have an interrelationship with each other, characterized in that each FPE element contains one or more security features comprising a chemical key represented with a set of molecules having different absorption or emission spectra, preferably said banknote comprising “n” FPE elements and “m” luminescent compounds, providing n*m potential combinations of secure FPEs dispatched in each banknote.

A typical banknote is shown in Fig 2 above (taken from the patent application) and has a variety of features for added security such as a substrate (0), a flag (10) and security features being a serial number (1 ), value numbers (2; 3) (wherein one of said value number is made of a colorshifting ink), an intaglio printed design (4), patterns made of a luminescent ink (5), luminescent fibers (6) incorporated in the substrate (0); a security thread (7), a transparent window (8) and a hologram (9).

The invention describes a banknote which has at least 2 FPE elements and these are designed to relate to each other and to the other security elements to provide the authentication mechanism.  Various modes of operation are described including the ability for the FPE to be capable of additional features such as being configured to interact, for example, with a computer and/or a mobile phone.

One example provided is if a banknote having added FPE features is stolen, the owner, for example, using a mobile phone already containing the data related to the banknote (e.g., in a storage device) can send a communication to (e.g., all banks around the world), identifying the banknote as stolen, to be sure that the banknote is identified as stolen and/or is no longer valid. In other embodiments, the FPE may be operable to send a signal to the owner’s mobile device when a banknote belonging to the owner is used. Thus, if the banknote is stolen, when the thief attempts to use the stolen banknote, the owner is notified, and can contact the police. The embedded FPE may also provide traceability capabilities for the banknote, so that, for example, a location of the stolen banknote can be determined.

Phil’s Comments:

This is a further example of the way flexible printed electronics can enhance the practical usefulness of everyday things.  The examples here also include security aspects which in itself is a huge technology field for the detection of counterfeiting and theft.  The secret is the ability to make these FPE elements small enough and self contained to work over a long period without the need for a separate power source.  Passive RFID elements are now very common and in everyday use.


Printed Electronics and Spiders

What on earth have spiders got to do with printed electronics?  Well, as is often the case, nature shows us how to do really difficult tasks in quite spectacular ways.  Spiders are well known for their webs, approximately 40,000 species of spider exist many of which produce thin silk fibres spun from pressurized abdominal sacs containing a polymeric solution. These sacs eject tiny jets that dry in-flight to produce the fibres with diameters of approximately 2.5 to 4.0 microns and are used to make the intricate patterned webs we see all around us.  Studying these natural processes has led to the development of microfluidic liquid jet printing and hydrodynamic printing concepts.

A recent patent application US20160129634 was published on 12 May 2016 by inventors David Keicher and Adam Cook of the Sandia Corporation and describes how this process can be used to create very thin inkjets suitable for use in direct printed electronic applications.

JetSummary:  The present invention is directed to an apparatus for two-fluid hydrodynamic printing, comprising a coaxial tube assembly, comprising an inner tube having an exit orifice for flowing an ink stream therethrough and an annular outer tube for flowing a sheath fluid therethrough wherein the sheath fluid has a higher velocity than the ink stream such that the ink stream is hydrodynamically focused by the outer sheath fluid upon exiting from the exit orifice of the inner tube. The apparatus can further comprise a focusing nozzle downstream from the exit orifice of the inner tube for further focusing of the ink stream therein. The apparatus can further comprise means for removing the sheath fluid from the ink stream downstream from the exit orifice of the inner tube and a recirculation channel for recirculating the removed sheath fluid. For example the ink can comprise polyvinylpyrrolidone and the sheath fluid can comprise water, alcohol, or a combination thereof. The focused ink stream can be deposited on a substrate.

Print results using two-fluid hydrodynamic focusing yielded a 30 μm wide by 0.5 μm tall line that suggests that the cross-section of the printed feature from the print head was approximately 2 μm in diameter. Printing results also demonstrated that complete removal of the sheath fluid is not necessary for all material systems. For example, hydrodynamic printing of two fluids enables printing of insulated conductors and clad optical interconnects.

The inventor D. Keicher also has a granted patent US8919899 which describes the same basic principle and in my view is relevant prior art to this application.

Phil’s Comments:

Printed electronics requires some very tight specifications for line width and resolution if the resultant printed tracks are to work reliably and meet the designs required by modern electronic circuits and components.  The conductive tracks often require liquids with specific properties which are not always suitable for inkjet nozzles or the typical methods of ink droplet formation.  The technology described here produces very narrow liquid lines on the substrate and is an interesting alternative for direct printed electronics.


How to generate a Patent Landscape

When you work in a particular technology area it is often useful to understand who else is working on the same technologies and who may be patenting or inventing aspects of the technology.  A patent landscape is the name given to a study of who holds these patents and the detailed understanding of trends in terms of numbers of patents granted; regions where the most patents are filed; understanding prior art and where potential gaps are for working on improvements or new features.  In addition, links between assignees and inventors (in particular any evidence of universities or research centres working with companies) can be very useful for finding collaborators or third parties who may be interested in joint research and development.

There are many organisations that provide this sort of information for a price and will provide a nice visual overview but when you are not really sure exactly what you are looking for it is much better to try out a few searches yourself and explore the landscape so that you know what you are up against and how complicated the landscape might be.

One organisation that provides this type of information together with some analysis is the World Intellectual Property Organization (WIPO) and, best of all, it is free!  The system is called PATENTSCOPE and is very simple to use.  It can be found at

Let’s now try and get a quick overview of the Internet of Things.  This is a really exciting new technology area where everyday items can connect via the internet to one another and interact in useful ways.

Open the link and in the simple search box type in the phrase “internet of things” using quotes to show that it is a phrase that we want to search on.  Rather than searching just on the Front Page select Any Field as shown below:

Simple Search

Click on search and the results immediately show.

Search results

You can see that there were 8,230 patent documents found from all the databases (by default we searched all the English language databases).  If you click on the Analysis bar it will open up a window where you can see at a glance which countries are filing patents, how many, who the top inventors and applicants are and what the timeline trend looks like.  You can also see the data graphically if you choose the various options in the window.  Some examples are shown below:

analysis view

graph view

The items in the table are all clickable so you can drill down to examine patents from any of the inventors or companies very quickly, or you could examine who first started filing in 2010.

The pie chart can be quite useful to see a breakdown of the main patent classification codes which give some idea of the technology areas covered.  An explanation of IPC and CPC codes can be found here:

pie chart

One problem with the data is that it is not standardised, for example you can see that Samsung appears under different names in the table so that you would need to add these together to get a proper feel for how many of the patent documents are owned by Samsung.  If you do this you find it is over 700, nearly 10% of the total.  Across all the patents you can see that the last 2 years accounts for around 75% of the total number.

If you wanted to explore the data in more detail you are allowed to download the results into an excel spreadsheet (10,000 records is the limit), however, you need to be logged in with a free account to be able to do this.  From the spreadsheet you can unravel a lot more detail about other companies and inventors filing, start to explore trends over time and look at granted patents.  In this dataset for example there are only 2.5% of the US patents actually granted, clear evidence that this is an emerging technology and there is quite a race to get the technology protected by patent rights.

I hope this brief overview has given you some idea of how to get a quick insight into the patent landscape of a particular technology area.  As always, do contact me if you have any questions or want a detailed landscape of your own technology area.

Update on Spray-on Solar PV

In a previous post I reported on a number of patent applications related to transparent solar panel technology that could be manufactured by a spray-on process.  This technology was being developed by Prof Xiaomei Jiang under a research agreement with New Energy Technologies Inc.  This company has now changed its name to Solar Window Technologies Inc. and there is much less evidence of the spray-on approach in their technical information suggesting that they are less confident that spraying will be a viable manufacturing route.

The patent applications have been going through examination and until quite recently there had been no granted patents emerging with the spray-on process as the key manufacturing method.  However, on 4 Aug 2015 the US20130255757 application was granted as US9099605 and as far as I am aware becomes the first granted patent with a spray-on process for PV panels.

Phil’s Comments:

I noticed that the first claim had to be modified before the examiner would allow it.  It has been somewhat narrowed in scope to include a 48h at 60°C heating step for the P3HT and PCBM before spraying multiple layers to a final thickness of between 200 and 300nm.  It was necessary to include this to avoid prior art found in the scientific literature which indicated a spray method but the layer needed to be thicker than 1.2 micron.  Other prior art also made mention of the heating requirements but failed to specify the layer thickness. Similarly, where layer thickness was specified in the prior art, it did not teach the heating steps were essential.


3D Printed Electronics – the next disruptive technology?

A patent application published on the last day of 2014 could easily have gone unnoticed but I believe it could be one of the next major breakthroughs in printed electronics.  The application has the title PRINTED THREE-DIMENSIONAL (3D) FUNCTIONAL PART AND METHOD OF MAKING and can be viewed by clicking on the link: WO2014209994.  The technology has been developed in the Research labs of Professor Jennifer Lewis at Harvard University.  The Lewis Lab team have been working for some years on multiple technologies including 3d printing, conductive inks for printed electronics, composite materials and micro-batteries.   This patent application describes various embodiments of a 3D functional part, for example one of the paragraphs states:

A method of printing a 3D functional part comprises, according to another embodiment: forming one or more portions of a 3D structure using a 3D printing method; positioning at least one functional electronic device on an exposed surface of the one or more portions; and forming conductive interconnects to and from the at least one functional electronic device using a 3D printing method. The method may further comprise, in some embodiments, forming one or more additional portions of the 3D structure using a 3D printing method. The one or more additional portions of the 3D structure may at least partially cover the at least one functional electronic device.

The method uses a printer with at least 2 printheads so that you can co-print both a matrix material and a conductor.  Electronic components can be manually inserted while the 3D printing operation is temporarily halted and then overprinted to embed the device.  One of the advantages of a direct write printing action that can move in all three axes is that the functional electronic devices can be orientated at any angle in the 3d structure and the conductive filaments are not constrained to a planar pathway as is typical of PCB boards.  The reader can refer to the patent application for more details of the materials for the matrix and the conductive inks but better still I refer you to the spin out company Voxel8 that plans to release this 3D printed electronics platform towards the end of 2015.  The patent application has a priority date of 24 June 2013.  This is an impressive time from filing the technology to a commercial device.  The first announcement of the 3D printer was made at CES 2015 back in early January.

Their promotional website can be found here.  I have included an image of the printer along with one of the devices made on it.

printed device Voxel8Printer

Phil’s comments:

3D printing continues to be an exciting area with many opportunities for prototyping and with the improvement in print heads and materials the devices are becoming more robust to the point that 3D printed components are now as good as their traditionally made counterparts.  The technology described here allows embedded electronics to be included in the 3D printing process.  Voxel8 will leverage ink designs from the Lewis research group, including those that enable 3D printing of resistors, dielectrics, stretchable electronics and sensors, and even lithium ion batteries.  I expect to see a significant number of patent applications emerge as part of this patent family and then further new applications as the materials and processes are developed.

I would like to thank Arthur Berman who contacting me for an opinion on this technology which then prompted me to write the article.

Printed Electronics card with piezo-powered indicator

I came across a recently granted patent that describes a printed card such as a business card with a display that is powered by a built-in piezo power source. This is a neat printed electronics application that gets around the problem of needing a battery to operate any device such as an indicator or display printed on the substrate. Although there are “printed electronics” batteries they tend to require encapsulated electrolytes to fabricate them and so are not entirely compatible with low-cost printing processes.

The patent is US8959734 and was published on 24th Feb 2015. It has a priority date of 16th Dec 2010. Details of the inventors and assignee are summarised below along with the abstract:

Inventors: Daniel; Jurgen H. (San Francisco, CA), Ng; Tse Nga (Mountain View, CA)

Assignee: Palo Alto Research Center Incorporated (Palo Alto, CA)


An interactive card or the like employs a piezoelectric charge generator (piezo-strip) for temporarily driving an indicator. The piezo-strip may be displaced (bent) in order to generate charge to drive the indicator. Printed electronic processes are utilized to produce the indicator and/or the piezoelectric charge generator. An indicator is formed on a substrate by way of a printed electronics process. A displaceable region of piezoelectric material associated with the said substrate is formed by way of a printed electronics process. Electrical interconnections are formed on said substrate by way of a printed electronics process. The electrical interconnections connecting said indicator and said first region of piezoelectric material such that displacement of said first region of piezoelectric material generates a voltage therein that is provided to said indicator in order to actuate said indicator and thereby indicate the displacement of said first region of piezoelectric material.

The drawings give a pretty good idea of the invention and its construction. I’ve reproduced two sets of figures below to show this but there are more in the patent that you can view.

Fig1_Fig2 Fig5_Fig6

FIG. 1 is an illustration of a display-capable business card with piezo-strip according to an embodiment of the present disclosure.

FIG. 2 is an illustration of the display-capable business card with piezo-strip according to FIG. 1, showing the deflection of the piezo-strip and the resulting actuation of an indicator.

FIG. 5 is a photograph of a display-capable business card with piezo-strip and template over an indicator according to another embodiment of the present disclosure.

FIG. 6 is a photograph of the components of the display-capable business card with piezo-strip and template over an indicator shown in FIG. 5.

Claim 1 provides the legal statement that defines the invention:

1. A method of forming an interactive card with indicator on a substrate, comprising: forming said indicator on said substrate by way of a printed electronics process; forming a displaceable region of piezoelectric material associated with said substrate by way of a printed electronics process; forming electrical interconnections on said substrate connecting said indicator and said first region of piezoelectric material such that displacement of said first region of piezoelectric material generates a voltage therein that is provided to said indicator in order to actuate said indicator and thereby indicate the displacement of said first region of piezoelectric material, said electrical interconnections formed by way of a printed electronics process, wherein said first region of piezoelectric material is formed over a piezo-strip region of said substrate; and partially disconnecting said piezo-strip region from said substrate in order to permit displacement of said piezo-strip region independently from the remainder of said substrate.

Phil’s comments:

Piezo technology does offer quite a few opportunities for where a brief amount of power is required to trigger a device. This patent describes one use illustrated above but also extends the ideas to other applications such as switches or sensors that can indicate if vibration or bending has happened. Another application detects liquid levels by sensing where the liquid moves a series of vertical flaps on the sensor by its swirling action. I have not seen any commercial applications of this but am aware of a Swiss company that uses the piezo effect to produce a keyboard and they recently demonstrated this integrated with one of Plastic Logic’s electrophoretic displays (see here).

Aqueous Conductive Silver Ink

Printed electronics is continuing to grow as more and more applications are developed and commercialised.  One of the key stumbling blocks continues to be the practicalities of printing narrow conductive tracks and the ease of use of the materials and processes involved.  One of the key system components, often taken for granted,  is the ink.  The majority of conductive ink compositions in use today are solvent-based thick film systems designed for low speed screen printing.  Water based conductive inks and coatings offer significant ecological advantages over solvent-based compositions, as the latter release solvents into the atmosphere on drying.  Aqueous conductive inks, however, have so far not offered the high conductivity, or low electrical resistivity, achievable with solvent-based formulas.

Sun Chemical Corp. have just been granted a patent for an aqueous ink with high conductivity and good printing properties.  This invention more specifically relates to an aqueous conductive silver ink suitable for use in RFID and other electronic technologies. The composition is highly conductive and requires reduced drying energy. In addition, it may be applied to low cost substrates via high speed printing processes. The key components of the ink formulation include: (meth)acrylic copolymer or salt thereof; conductive particles; an anionic surface wetting agent; defoamer and water.  The first claim suggests the ink can be up to 80% water depending on the amount of the other ingredients.

The patent is US8709288 and it was issued on 29 April 2014.  The Inventors are Jason Rouse and Dave Klein.

The independent claims from the patent are listed below:

1. A method of forming a conductive pattern on a substrate comprising applying a conductive composition comprising (a) metallic silver conductive particles, (b) water soluble styrene/(meth)acrylic copolymer, (c) an anionic wetting agent, (d) defoamer and (e) 10 to 80% water, the composition providing a sheet resistance of less than 0.83 ohms/sq, on the substrate and drying the composition.
34. A method of forming a conductive pattern on a substrate comprising applying a conductive composition consisting essentially of (a) metallic silver conductive particles, (b) water soluble styrene/(meth)acrylic copolymer, (c) an anionic surfactant, (d) defoamer and (e) 10 to 80% water, the composition providing a sheet resistance of less than 0.83 ohms/sq, on the substrate and drying the composition.
37. A method of forming a conductive pattern on a substrate comprising applying a conductive composition consisting of (a) metallic conductive particles, (b) water soluble styrene/(meth)acrylic copolymer, (c) an anionic surfactant, (d) defoamer, (e) 10 to 80% water, and optionally another solvent, the composition providing a sheet resistance of less than 0.83 ohms/sq, on the substrate and drying the composition.

The differences above are subtle but important, claim 34 describes the composition with an anionic surfactant rather than a wetting agent, and claim 37 describes a more general formulation with any metallic conductive particle and optionally includes another solvent.  Each claim includes the requirement that the composition provides a resistance of less that 0.83 ohms/sq on the substrate.


Phil’s Comments:

Good to see that research into inks suitable for printed electronics is providing environmentally acceptable formulations.  Reducing solvents and also reducing the energy requirements for drying are all good directions for the ink design.  We sometimes forget the huge demand put upon the inks we use, for example they need good abrasion and chemical resistance when dried so that they are not easily scratched or wiped off during subsequent uses, they need to have proper rheology and substrate wetting properties to obtain good ink transfer and graphic reproduction. Additionally, the ink should possess good flexibility and thermal stability to withstand the physical deformation to which the substrate may be subjected.  Let’s remember the research that goes into the inks when we next see a printed electronics design in use!