Microfluidics – an interesting blend of MEMS, IC technologies, and paper

At a recently held MEMS Technology and Business Symposium hosted by MEPTEC (the Microelectronics Packaging and Test Engineering Council) in San Jose, Calif., many advances in MEMS technology focusing on health care demonstrated the implementation in silicon of pumps, valves, chemical sensing, and still other functions. Additional research on the use of paper rather than silicon as the substrate shows a lot of promise since paper is very inexpensive, is compatible with many chemical/biochemical/medical applications, and it transports liquids using capillary forces, thus eliminating the need for a MEMS-based pump.

This combination of microscopic mechanical functions, silicon control circuits, and paper-based sensors, is making possible a wide range of products for the medical eHealth market and for industrial and military applications. As demonstrated in a presentation by Dr. Gisela Lin from University of California at Irvine, silicon technology can now implement all the functions to form a “lab-on-a-chip” – bubble pumps, fluid channels, a mixing chamber, a polysilicon heater, and valves, all interconnected and controlled by an off-chip processor (Figure 1). The technology is similar that used by the ink-jet printer print heads.

Figure 1: Implemented in silicon, this lab-on-a-chip can pump liquid through fluid channels, warm the liquid using polysilicon heaters and control the liquid flow into mixing chambers via electrically controlled valves.



And the innovation doesn’t stop there as Dr. Janusz Bryzek, the Vice President of Development for MEMS and Sensing Solutions at Fairchild Semiconductor pointed out in the conference’s opening presentation. Driving that development is the growth in the wearable health monitoring market – according to ABI Research, a market research company, in 2010 just 10 million monitoring devices were deployed and all for mostly sports and fitness applications. However by 2014, ABI analysts expect the market to grow to 420 million wearable health monitors, with about 59 million used at home.

Ongoing research at several universities is examining the ability of directly printing sensors on skin, allowing direct-contact measurements. For example, at the University of Illinois at Urbana-Champaign, researchers have succeeded in printing a triple-function sensor that senses the skin’s temperature, strain, and hydration state, all of which are useful to track general health and wellness, as well as for monitoring wound healing (Figure 2). An even more complex sensor circuit developed at the University of California at San Diego combines ECG and EMG sensors, temperature sensors, strain gauges, photodetectors, a wireless antenna, a wireless communications oscillator, a power pick-up coil to capture transmitted power, and an LED—all in a thin layer of rubbery polyester that allows the senosrs to stretch, bend, or wrinkle. Such a solution can provide a means to monitor premature babies to detect the onset of seizures, which could lead to epilepsy or brain development problems (Figure 3).

Figure 2: Sensors directly printed on the skin by researchers from the University of Illinois at Urban-Champaign can sense temperature, strain, and hydration state.



Figure 3: Multiple sensors as well as a wireless power pick-up coil and simple transmitter and antenna allow this sensing solution in a thin flexible polymer from the University of California at San Diego, be used for various patient monitoring applications. One such  application could be to monitor premature babies to detect the onset of seizures, which could affect the baby’s development.


In addition to these advanced research prototypes, there are many real examples of Appcessories – application software and peripherals that link to and run on smartphones such as the Apple iPhone. Bryzek highlighted just a few – Proteus offers digestable sensors that send wireless signal through the body to a receiver. The sensors measure heart rate, activity, and respiratory rate. GeneZ offers a low-cost DNA chip containing up to 64 reaction of less than 1 microliter in volume – assay time is 10 to 30 minutes and the cost is less than $1000 (the chip cost is just $5 to $10). Uchek from MIT uses the smartphone’s image sensor and a software application available on the Apple App Store to read test strips and it can detect up to 25 diseases such as diabetes, urinary tract infections, and pre-clampsia. The test strips can also measure the levels of glucose, proteins, ketones, and still other health factors.

Putting a doctor in a pocket, Scanadu released three home diagnostic tools that leverage the sensors and processing capability in a Smartphone to perform imaging, sound analysis, molecular diagnostics, data analytics, and run a suite of algorithms that can create a comprehensive, real-time picture of your health. A “Lab on a Chip” developed by STMicroelectronics is employed by Veredus Laboratories to detect the current subtype of H7N9 (Avian Flu) along with other types of human subtypes of Influenza A. The Lab on a chip combines two powerful molecular biological applications – polymerase chain reaction and microarray and can detect the infection with a high accuracy and sensitivity within two hours while providing genetic information on the infection that traditionally would take days to weeks to learn. One last example provided by Bryzek is a device that performs DNA and RNA sensing – Nanobiosim, an engine that integrates physics, biomedicine, and nanotechnology that can rapidly and accurately detect genetic fingerprints from any biological organism.

Dave Bursky, Technology Editor

For conference program details, go to  https://www.meptec.org/meptec11thannual.html

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