Sensing the Future

Scientists are scrambling to beat each other to the punch, and instrumentation companies are monitoring (no pun intended) the situation closely and aggressively. At stake is the inside track on a technology that promises to change the course of utility operations, and perhaps much more.

Inventor Dr. Junhong Chen (right) and former student Dr. Ganhua Lu see huge potential for their small sensor.

The breakthrough discovery is the real-time detection of bacteria and other constituents present in water, with the added capability to instantly communicate the data to a central location. For drinking water utilities, it’s the arrival of “intelligent water distribution,” utilizing a network of these remotecommunication, real-time sensors to detect contaminants throughout the distribution system. Though the technology is not yet mature, these sensors are most definitely coming… and their impact will be profound.

A New World Of Capabilities

“You can’t control what you can’t measure” is a broadly applicable adage (coined by software engineering guru Tom DeMarco), but is particularly relevant to water quality. Imagine the control operators would (or will) gain by being able to remotely see contaminants of any type, anywhere in the pipeline — from plant to tap — in real time. No longer would samples need to be gathered in the field and taken back to the lab for testing. When it comes to bacteria and viruses, the time lag between contamination and discovery that currently exists would be essentially eliminated, meaning less community exposure and illness. The benefits these enhanced capabilities bring to public health and utility operations are easy to recognize.

But what else does real-time sensing bring to the table? The possibilities are virtually limitless.

Because the sensors can be engineered on an ad hoc basis — that is, customized for specific needs and constituents — the technology has the potential to be utilized for almost any application involving liquids, and to measure for just about anything. The industrial and wastewater applications are further down the line, however, as the sensors are engineered to become more robust. Initially the technology will be used to detect and communicate the presence of drinking water contaminants, specifically E. coli and heavy metals (e.g. arsenic, cadmium, chromium, lead, and selenium).

Research And Development

As you read this, Dr. Junhong Chen is working feverishly. So, too, are his competitors. The goal is to be the first to market with this new sensor technology, and the market won’t respond unless the price point is reasonable. According to Chen, director of the U.S. National Science Foundation Industry- University Cooperative Research Center (I/UCRC) on Water Equipment and Policy at the University of Wisconsin-Milwaukee (UWM), that price point is $10 per sensor. A second challenge is to ensure the resiliency of the units in the field, since the very idea of the technology is to “set it and forget it” (for at least a year, and then only to change out the battery), thereby dispensing of the typical O&M effort of sending personnel to multiple sampling sites. The third obstacle is miniaturization of the sensors, so that many individualized contaminant detectors can be housed on a single probe.

“In the size of a fingernail, we can potentially integrate hundreds of sensors,” said Chen, who described the patent-pending technology as the “Holy Grail” for the water industry.

Figure 2. The incredibly shrinking sensor (miniaturization is ongoing) in comparison to a quarter.

“We’ll have sensors attached to the filter cartridge, to the pump, and to the water meter so that — in addition to whatever conventional functionality the equipment is providing — we can see contamination levels,” Chen predicted. “That’s the future.”

The rapidly developing technology is being realized due to the development of graphene, which earned 2010 Nobel Prize in Physics for the University of Manchester researchers who discovered it. At just one atom thick, graphene is “not only the thinnest [material] ever, but also the strongest,” stated the Royal Swedish Academy of Sciences, presenters of the Nobel. The Academy also noted that graphene conducts heat better than all known materials, and conducts electricity at least as well as copper. Graphene’s potential for electronics was recognized from the start, as it was predicted to make transistors that are substantially faster than today’s silicon transistors.

Using this knowledge as foundation, inventors at the Water Equipment and Policy Research Center (WEP) — established in 2010, the same year graphene earned the Nobel — set out to create a real-time, “intelligent” sensor for water/wastewater quality and control. Dr. Junhong Chen is leading the research, working with his colleagues in the WEP network. Based in Milwaukee, WEP includes two universities (UWM and Marquette University), as well as seven industry members — a mix of businesses (A.O. Smith, Badger Meter, Baker Manufacturing, Pentair, Marmon Water), a consulting company (Gannett Fleming), and the local municipality (Milwaukee Metropolitan Sewage District).

The result is what Chen called a “revolution for water-related equipment” — graphene oxide (GO) fieldeffect transistor (FET) sensors. According to UWM, the new sensors offer the following advantages over current technology:

  • Faster – Rapid response for real-time monitoring
  • Highly sensitive – Detection of E. coli 0157:H7 concentrations down to 1 CFU (colony-forming unit) per mL
  • Scalable – Fabrication can be scaled up with good reproducibility/high electrical stability
  • Inexpensive – Materials for fabrication are relatively inexpensive
  • In situ detection – Sensors can be placed directly in the water system

You can stick the sensor onto anything to tell you what’s in the water, Chen projected.

Right now, the technology has been proven for E. coli, which is first on the docket for real-world application. Chen estimates that it will be a year or more before reaching that point, with sensors for the detection of heavy metal ions to follow thereafter. Now that the science has been established, however, the realization of this soon-to-be transformative technology is inevitable. The progress could be hastened by additional funding — the National Science Foundation and the EPA, for instance, have programs to support innovation — and there is surely a host of competitors worldwide striving toward the same goal.

I would say everybody would be willing to invest in this technology, said Chen.

  • * Reprinted with permission from Water Online Magazine (February 2014)