Printing Electrodes for Diagnostic Sensors
Printing Biological Materials
Over the past two decades, more accurate, convenient and earlier diagnoses have become a key strategy to reduce medical costs. This trend toward improved diagnostic technology will only grow in importance in the future as the first Baby Boomers turn seventy (in 2011) and as millions of people in less-developed nations begin to utilize more Western healthcare technology as their countries grow richer. In addition, healthcare experts have come to believe that diagnoses are most effectively delivered if they are made as close to the patient as possible. A quick read of a patient's condition at his or her bedside is preferred over a test sent to a lab that may take critical hours or days to interpret.
All this implies that the market for point-of-care and home diagnostic products will expand over the next few years. In our recently published report on printed and large-area sensors, NanoMarkets examined how low-cost printing technologies can help diagnostics respond to the trends outlined above. The path toward this goal of printed sensors has already been forged in the area of self-testing for diabetics, where printed test strips have helped bring accurate digital diagnostics to the tens of millions of diabetics throughout the world.
These printed test strips are an important market in their own right. NanoMarkets estimates that they will generate about $2.4 billion in revenues in 2010. The hope that printing holds out, however, is for lower costs for much more complex diagnostic products, especially those based on genomics and proteomics--two scientific areas that will likely be at the core of diagnostics in the future.
Genetic testing in particular is already a major component of personalized medicine, itself one of the big medical hopes for the future and certainly one of the most discussed. (The Director of the National Institutes of Health just wrote a book on the topic.) Genetic testing and personalized medicine are linked because, without a good take on a person's genetic makeup, it is hard to create a therapeutic and illness avoidance program that is specifically tailored to their needs. New kinds of medical testing requirements are also likely to emerge, since the emphasis is now shifting from DNA to proteins. That is, the genomics era is already making way for the era of proteomics; it is proteins and not genes that are the majority of the true drug targets.
Yet, to date personalized medicine has failed to take off in the manner that has been predicted by its fiercest advocates. One reason is that genetic testing is still a relatively expensive procedure. Indeed, this point can be made about sophisticated diagnostic tools in general. To bring these to the patient's bedside or into their home will take significant cost reductions. We believe that printed electronics, or more accurately functional printing, can help cope with this cost constraint. Specifically, NanoMarkets sees three main opportunities for printed electronics/functional printing in this regard. These are: (1) printing electrodes; (2) printing biological materials; and (3) using functional printing technologies to create large-area diagnostic biosensors.
The opportunity that diagnostics presents most immediately for printed electronics is the creation of low-cost electrode layers for diagnostic biosensors. In fact, companies are already doing this, often using screen printing. There is nothing spectacularly novel about fabricating electrodes using printing. In many areas of electronics, screen printing has been used to create electrodes for decades. As such, biosensors represent a new, potentially high-volume market for a range of existing products and procedures, most notably the broad range of conductive inks that are available from several well-established suppliers.
There are a few aspects of electrodes for diagnostic biosensors that make this opportunity a little different from say the use of screen printing to create electrodes in a membrane switch for a kitchen appliance. Biosensors (by contrast to the switch) are high-performance devices that may therefore require electrodes with high levels of conductivity. With this in mind, NanoMarkets believes that, diagnostic biosensors may well serve as a good market for the new breed of nanoparticulate conductive inks that have emerged in the past few years and which offer higher conductivity than the old-style thick-film metallic pastes. We also note that while other biosensors tend to use silver or carbon electrodes, gold is often the electrode material-of-choice in medical devices.
Printing electrodes is unlikely to have a significant impact on the diagnostic sensor business, but the cost reductions that it will produce could certainly help bring about lower cost diagnostics. In addition, printing sensor electrodes is an indicator of a future in which complete (or at least near-complete) diagnostic biosensors are created by printing layered structures on an appropriate substrate. This would seem to suggest that printing would be used not just to create electronic functionality but to lay down biological materials as well.
This more thorough approach to printing sensors could lead to disruptive changes to the cost of diagnostics. There is already good evidence that printing, specifically inkjet printing, is an excellent way to deposit biological materials. FujiFilm Dimatix, the manufacturer of one of the best-known small functional inkjet printers, reportedly already gets a significant share of its business from customers wanting to print biological materials. In addition, Agilent Technologies, which is the world's second-largest manufacturer of nucleic acid microarrays, prints the nucleic acids as part of its fabrication process and claims that its printed arrays demonstrate a high level of accuracy and reproducibility. The jetting technology used in Agilent's DNA microarray fabrication allows the printing of 185,000 features on a 1-inch x 3-inch slide with the potential for 400,000 features.
Without printing, the fabrication of microarrays can be both costly and complex, so low-cost fabrication processes such as printing are always welcome. Many firms still use photolithography to create microarrays. By contrast inkjet microarray printing is said to be far more flexible and customizable, only requiring a different software file to print a different array. Agilent says it can design and print a custom microarray at about one-tenth of the price of microarrays manufactured in the traditional manner.
This is all very impressive and speaks to considerable opportunities for sophisticated printed diagnostic sensors in the future. Nonetheless, NanoMarkets warns that firms and investors seeking to be active in the printed microarray space should not get too optimistic about this sector. For one, functional printing somehow never turns out to be as easy as it sounds. Secondly, with the rise of proteomics there is now considerable interest in the use of functional protein microarrays. Unlike DNA molecules, proteins are not as easy to attach to a substrate. In addition, proteins exhibit a wider range of physical characteristics than nucleic acids. This suggests that protein microarrays will not be as easy to create using jetting technology as DNA microarrays are currently.
Finally, there is the issue of how printing fits into the large-area sensor concept. Large area sensors are sensors that are embedded in a large (often flexible) substrate, creating what is, in effect, a large sensor array. There are several reasons why someone would want to create such an array. First, there are the advantages associated with any sensor array--more accurate readings and enhanced redundancy. However, the large-area sensor concept implies an integration of sensors and substrate in such a way that has not been found in conventional arrays.
Large-area sensors can be used in many applications including environmental monitoring and military applications. However, diagnostics are certainly another possible application. One example in the diagnostics space comes from the Scottish firm Frank Sammeroff, which has developed a range of patches that can be embedded with low-cost sensors for patient monitoring of glucose levels, body temperature, hypertension and cardiac condition.
Such patches are not typically created with printing today. However, it is easy to see how they might be in the future. Consider printing the sensors themselves on a flexible substrate and then perhaps also printing silver interconnects to ferry data to some kind of processor. In some cases, large-area sensors would be equipped with RFID tags that would connect to external databases and medical networks via secure encrypted transactions. And here again printing could come into play, since RFID antenna and (perhaps) the RFID chip itself could be printed.
Many of the applications for functional printing and printed electronics that we discuss in this article are just emerging from the R&D phase and as such are not yet generating significant revenues. However, as noted, printed diagnostic sensors seem to fit in well with two desirable megatrends in healthcare strategy: bringing diagnostics closer to the patient and the trend toward personalized medicine.
As such, we expect to see significant new business revenues coming from the areas outlined above. For example, by 2015, we would expect about $415 million in printed genetic sensors to be produced. How such opportunities will evolve is discussed in much more detail in our report on printed and large-area sensors.
Source: Medical Diagnostics: An Opportunity for Printed Electronics
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