A Bio Lab On A Chip

Micro-arrays, integrated electronics and photonics on a sliver of silicon let researchers probe for individual genes responsible for a disease. The DNA analysis chip is just a tip of how Micro-Electro-Mechanical-System (MEMS) technology can be applied to miniaturize devices. Partners can expect to see more of this technology in the future in devices like wireless terminals, printers, optical networks and appliances.

The semiconductor technology company STMicroelectronics has produced a silicon chip with micro arrays that support on-chip DNA analysis at the genetic level. When DNA from diseased and healthy sources is added to the silicon, it becomes a platform for genetic research into the cause of diseases. The monolithic (one-chip) array includes the sensing and supporting electronics.

A media group taken to Catania, Sicily in South Italy in September was shown a machine placing droplets containing DNA onto silicon; through a scanner, computer and software. The group then saw the array of color dots representing healthy gene pairs and those that were likely candidates for specific diseases.

The array of tiny dots on a silicon surface allow genetic researchers to accurately place a single polynucleotide strand of the twin-strand, double-helix DNA from individuals with specific diseases (the target DNA) along with a strand of healthy DNA as reference (the probe). The objective is to find out the precise difference between the two DNA strands, thus identifying the genes that could be responsible for the disease. 

Like a lock and key, the two strands will come together completely if the specific deoxyribose and phosphate groups are complementary, forming strong covalent (chemical) bonds. If there is a difference, that pair will not form the bond, showing a different color characteristic. One end of the DNA strand itself forms a covalent bond with the silicon, anchoring it firmly in place.

The chromatically marked DNA fluoresces when excited by electrons, and this can be detected by photo-sensors. Different colors indicate whether the gene pairs have paired correctly or not, and therefore whether they are identical or different. 

Such a micro-array silicon platform for DNA allows the monitoring of expressions of 10,000 or more genes at a time. And the single piece of silicon contains the active electronics, and even the micro-channels carrying the DNA fluid, all integrated into one piece of silicon, increasing the speed of analysis and reducing its cost. Capillary forces in the micro-channels can even transport the solution with the DNA.

The silicon chip integrates even the photo-sensors. According to the company, this is an achievement, as silicon´s optical properties are not suited to either photoreceptor or light source use, which is why devices like LEDs tend to use gallium arsenide and other “III-V” compounds, so called because they belong to groups III and V of the periodic table of elements.

But this would mean that adding an LED or photoreceptor to a silicon device would involve multiple stages and devices. 

To integrate the whole device out of a single piece of silicon, STMicroelectronics engineers “doped” the silicon with specific ´impurities´ to change its optical properties, in this case to create a photoreceptor element on a silicon chip, which can detect the fluorescence and color of the DNA just above it. 

Thus, adding optical functions to silicon helps allow active DNA analysis within a silicon chip, and the integrated electronics in the same silicon senses and communicates the color changes in the DNA pairs in the array. Using silicon for the base substrate for the DNA analysis also has other advantages­mainly, a great benefit in signal to noise ratio. Glass itself would fluoresce, so such background noise from glass would have to be “subtracted” from the results of such an experiment.

Parallel with the silicon biosensor array development is ongoing research into DNA strands to explore genetic pairs as alternative memories, including research on organisms that change state or color after absorbing a photon, making them candidates for future ´optical storage´.

While yet at the research and testing stage, ST officials say they expect to manufacture the “gene platform” biosensors in a year for “simple stuff” and in three years for “more complex stuff”.

The $6.3 billion STMicroelec-tronics is the fourth-largest semiconductor company in the world. Headquartered in Geneva, Switzerland, ST has three regional headquarters in Dallas, Texas (USA), Singapore (Asia-Pacific) and Tokyo (Japan). It has 17 manufacturing sites across the world including Catania in Italy, the USA, and elsewhere. It is particularly strong in “system-on-chip” technology, and supplies chips to, inter al, Alcatel, Nokia, Philips, Siemens and Sony, inkjet print-heads to HP, and automotive electronics systems to DaimlerChrysler and Ford.

The ST group was formed in 1987 after the merger of SGS of Italy with Thomson of France. In May 1998, the company changed its name from SGS-Thomson Microelectronics to STMicroelectronics. Today, it has 43,000 employees (including over 1,000 in its India development center in Noida, UP), 16 R&D units and 39 design and application centers. The company is NYSE-listed (“STM”) since 1995.

Prasanto K Roy is Chief Editor of Dataquest.
He traveled to Catania, Sicily in South Italy at the hospitality of

STMicroelectronics. (CyberMedia News)

DNA ANALYSIS CHIP

What is DNA analysis chip (or Silicon Lab-on-Chip)?

Silicon Lab-on-Chip is a disposable, standalone, point-of-care, monolithic DNA analysis device developed by STMicroelectronics, which performs both DNA amplification and detection on the same chip.

What it does?

The DNA analysis device performs DNA amplification in microscopic channels buried in the silicon and then identifies DNA fragments on gold electrodes.

Who is it useful for?

The primary end use targeted by the DNA analysis chip is in medical diagnostics, to detect genetically related disease directly at the point of care without the delays of laboratory testing. It is a compact, inexpensive and rapid solution for point-of-care diagnostics

Why a compact solution?

Compared to traditional tests, the ST silicon lab-on-chip device offers a very compact solution that reduces the overall testing cost and delivers results in minutes. Using this technology, extremely small quantities of fluid can be analyzed. 

Since there is no practical way to clean the channels after use these devices are inevitably for single use only. In the conventional laboratory this method is done with bulky and costly equipment and can take several hours. 

What is the technology behind this device?

This device is based on
Micro-Electro-Mechanical-System (MEMS) technology that applies silicon-chip manufacturing technologies to produce miniature devices with a combination of mechanical, electrical, fluidic and optical elements. DNA amplification is performed using the Polymerase Chain Reaction (PCR) technique.

Where else is MEMS used?

STMicroelectronics develops and manufactures silicon MEMS devices using in-house-developed technologies covering a broad range of applications. The micro-fluidic technology used in the DNA analysis device builds on the company’s long experience in the manufacture of inkjet printer chips combining electronic and fluidic elements.

STMicroelectronics is particularly strong in “system-on-chip” technology, and supplies chips to, inter alia, Alcatel, Nokia, Philips, Siemens and Sony, inkjet print-heads to HP, and automotive electronics systems to DaimlerChrysler and Ford.