Manufacturing Bits: Aug. 5

Chemical weapon sensors
Using nanoelectromechanical system (NEMS) technologies and other parts, Sandia National Laboratories has developed a tiny gas chromatograph sensor for use in detecting toxic gases and chemical weapons.

Chemical identification involves the use of various instruments and systems. Larger systems are used in the lab. A portable version, called a mass spectrometer, is available in the market. But they less sensitive than the bigger lab-based instruments, according to Sandia.

Sandia has been working on smaller portable gas detection technologies using gas chromatography. Gas chromatography is a technique used to separate and analyze compounds.

Now, the agency has developed a small but fast gas chromatographic sensor using NEMS cantilever resonators for detection. A valve-based stop-flow modulator is also used in the system.

NEMS are like MEMS or microelectromechanical systems. MEMS are small devices with moving parts. Ink jet printer heads and pressure sensors are examples of MEMS devices. In comparison, NEMS integrate transistor-like nanoelectronics with moving parts.

With Sandia’s device, meanwhile, the unit has demonstrated the ability to separate and analyze a 29-component mixture in less than 7 seconds, according to Sandia. The system also detected compounds that simulate mustard gas and phosphonate-based nerve agents.

“With rapid analysis, operators can learn about an exposure to toxic gases in time for people to take personal precautions, evacuate an area and mitigate potential damage,” said Joshua Whiting, an analytical chemist at Sandia.

A Sandia researcher examines a gas sensor that could be used in a portable system to detect chemical weapons or airborne toxins. (Photograph by Randy Montoya)

Earthworm chips
The Riken Center for Biosystems Dynamics Research (BDR) has developed a small MEMS-based valve device that is powered by earthworm muscle tissue.

The on-chip muscle-driven valve opens and shuts with high force and doesn’t require a battery. The device could one day be used for surgical implants and other applications.

The device combines MEMS technology with living materials, which falls under the category of bio-MEMS. Bio-MEMS can be a MEMS device, which is used in biological applications. One example of a bio-MEMS device is a sensor that is implanted into a living body. The sensor monitors a biological process.

Another application is an actuator. Part of a machine, an actuator controls a mechanism of a system. For example, it opens and closes a valve. Typically, actuators are MEMS-based devices. In contrast, a bio-MEMS actuator is powered by chemical means.

Riken’s bio-actuator involves a 2- x 2cm chip. There is a valve and a microfluid channel on the chip. The valve is controlled by the contraction and relaxation of an earthworm muscle via a chemical reaction.

The tissue provides high force, which could be sustained for minutes. A 1cm × 3cm sheet of earthworm muscle produces a force of about 1.5 milli-newtons over a two-minute period. The tissue reacts to a small amount of acetylcholine. “For muscles, the signal for contraction is the molecule acetylcholine—which is delivered by neurons—and the energy source is adenosine triphosphate (ATP)—which exists inside muscle cells,” according to Riken.

A valve on a 2 × 2 cm chip powered by earthworm muscle. (top) Design of the valve seen from above. A sheet of earthworm muscle covers a pushbar that sits above a microchannel. (bottom) Cross-sectional views through the microchannel when the valve is open (left) and closed (right). Still images of fluorescently labeled microparticles were taken from the video clip at the top of the article. (Source: Riken)

“Not only can our bio-MEMS work without an external power source, but unlike other chemically driven valves that are controlled by acids, our muscle-driven valve runs on molecules that are naturally abundant in living organisms,” said Yo Tanaka from Riken. “This makes it bio-friendly and especially suited for medical applications in which the use of electricity is difficult or not advised.

“Now that we have shown that on-chip muscle-driven valves are possible, we can work on improvements that will make it practical,” said Tanaka. “One option is to use cultured muscle cells. This might enable mass-production, better control, and flexibility in terms of shape. However, we will have to account for the reduction in the amount of force that can be produced this way compared with real muscle sheets.”

Drug delivery devices
The Houston Methodist Research Institute has developed another form of a bio chip–an implantable drug delivery device that will be tested in humans in space.

The device, called a nanochannel delivery system (nDS), consists of a microchip that is the size of a grape. Using a Bluetooth-enabled wireless communication function, the nDS device provides a controlled release of prescription drugs via remote control. The device delivers drugs for months, even a year, before refills are needed.

The device will be tested on the International Space Station in 2020. The technology has already been demonstrated using enalapril and methotrexate, which are used in the treatment of hypertension and rheumatoid arthritis, respectively, according to researchers in a recent paper published in “Lab on a Chip,” a technical journal.

There are several drug delivery devices on the market. Pain or insulin implants rely on pumping mechanisms or external ports, according to Houston Methodist. These devices need refills every couple of months.

In contrast, Houston Methodist’s nDS device does not require pumps, valves or a power supply. Houston Methodist’s device is implanted under the skin. It uses a nanofluidic membrane based on silicon technology.

Using wireless technology, the device can be programmed and controlled for three different drug release settings–standard, decreased and increased.

“We see this universal drug implant as part of the future of health care innovation. Some chronic disease drugs have the greatest benefit of delivery during overnight hours when it’s inconvenient for patients to take oral medication. This device could vastly improve their disease management and prevent them from missing doses, simply with a medical professional overseeing their treatment remotely,” said Alessandro Grattoni, the chair of the department of nanomedicine at Houston Methodist Research Institute.