Albert Folch. Hidden in Plain Sight: The History, Science, and Engineering of Microfluidic Technology. Cambridge: MIT Press, 2022. Illustrations. 352 pp. $40.00 (cloth), ISBN 978-0-262-04689-3.
Reviewed by Benjamin Gross (Linda Hall Library of Science, Engineering and Technology)
Published on H-Sci-Med-Tech (October, 2022)
Commissioned by Penelope K. Hardy (University of Wisconsin-La Crosse)
At first glance, a ballpoint pen shares little in common with a pregnancy test or 3D printer. Yet, as Albert Folch points out, each of them manipulates fluids over very small distances to perform specific tasks. They are examples of microfluidic devices. Folch’s latest book, Hidden in Plain Sight: The History, Science, and Engineering of Microfluidic Technology, considers how applications relying on similar operating principles have transformed laboratory research, medical diagnostics, and precision manufacturing from the 1970s until today.
As the title indicates, the proliferation of microfluidics has received only limited attention from either academic or general audiences. Folch attributes this obscurity to industrial designers tasked with concealing the microfluidic underpinnings of consumer products behind user-friendly interfaces. To understand the history of microfluidics, he argues, it is essential to pry open these black boxes and reconstruct the investigative pathways that led to their commercialization.
Folch possesses the scientific expertise and professional connections to accomplish both of these tasks. A professor of bioengineering at the University of Washington, he is deeply familiar with major advances in microfluidics, including his own investigations into systems that detect cancer and test how various drugs affect tumor growth. His account draws primarily on published journal articles, supplemented with firsthand reflections from some of the field’s most noteworthy contributors.
In many respects, Hidden in Plain Sight resembles a textbook, complete with evocative full-color illustrations and inset boxes containing biographical vignettes and summaries of technical concepts. An introductory chapter provides an accessible overview of fluid mechanics, emphasizing how the properties of a material can change at smaller scales. Most notably, when fluids are constrained within very thin channels (i.e., less than a millimeter wide), turbulence becomes practically nonexistent, making it possible to precisely control their flow using electric fields or capillary action. The remainder of the book presents a series of case studies that demonstrate how researchers have capitalized on these behaviors to create increasingly sophisticated microfluidic devices.
Folch begins with a discussion linking a government-sponsored effort to design chemical instrumentation for space probes and a mainstay of the modern office. In 1971, NASA contacted Stanford electrical engineer James Angell about the possibility of building a gas chromatograph on a chip for the upcoming Viking missions. Over the next several years, Angell and one of his graduate students, Steve Terry, assembled the Stanford gas analyzer, which separated the components of an atmospheric sample as it passed through a 1.5-meter-long, 200-micron-wide channel coiled into a spiral that fit on a 5-centimeter-wide wafer. NASA ultimately chose not to send Angell and Terry’s analyzer to Mars, but the manufacturing processes they developed would contribute to the birth of another microfluidic technology. By the early 1980s, firms like Canon and Hewlett-Packard had repurposed their silicon-etching techniques to fabricate the integrated arrays of identically shaped nozzles that inkjet printers use to produce images.
The story of the Stanford gas analyzer introduces several narrative throughlines that will resonate with historians of science and technology. It illustrates that the discipline of microfluidics emerged from the interplay of government, academic, and corporate actors and that the “triple helix”—to borrow a phrase from Henry Etzkowitz, The Triple Helix: University-Industry-Government Innovation in Action (2008)—facilitated the transfer of fundamental research from the workbench to the marketplace. A similar dynamic is apparent in Folch’s chapter on high-throughput DNA sequencers. These instruments, which have become fixtures in forensics laboratories and hospitals, were originally invented in the 1990s by a team led by Berkeley chemist Richard Mathies under the auspices of the Human Genome Project and subsequently commercialized by various biotechnology firms.
Another recurring theme throughout the book is a constant drive toward miniaturization. Even before scientists started using the term “microfluidics” in the early 1990s, they recognized that reducing the scale of their experimental apparatus would permit chemical reactions to occur more quickly using smaller amounts of expensive reagents. Replacing traditional glassware with networks of microchannels also raised the possibility of conducting multiple tests in parallel, but the complexity of microfluidic designs remained limited by the need to manually measure and dispense liquid samples. Much as integrated circuitry allowed electrical engineers to circumvent increasingly dense networks of interconnections between discrete transistors, resistors, and capacitors (the so-called tyranny of numbers), researchers would only overcome this “tyranny of pipetting” with more effective microfabricated valves.[1]
The solution to that engineering challenge, along with many other advances in microfluidics, was contingent on the introduction of new materials. During the 1970s and 1980s, scientists repurposed photolithography and etching processes from the electronics industry to craft microfluidic devices from glass or silicon. Since these fabrication techniques required access to a clean room, such projects remained out of reach for most researchers.
That situation changed in the 1990s, when a group of researchers led by Harvard chemist George Whitesides started experimenting with poly(dimethylsiloxane) (PDMS), a transparent biocompatible polymer. By pouring PDMS over a microfabricated mold, a process Whitesides referred to as “soft lithography,” it became possible to fashion microfluidic devices in a university chemistry lab. Soft lithography accelerated the pace of prototyping and enabled a team at Caltech to produce the reliable PDMS valves needed to regulate flow in more complex microfluidic systems. Because it relies on molds forged in a clean room, Folch observes that soft lithography represented only a partial step toward the democratization of microfluidics. During the twenty-first century, however, researchers have embraced alternative materials, such as micropatterned paper or 3D-printed hydrogels, a promise to streamline the assembly of microfluidic applications and make them more affordable to the public.
With chapters covering everything from personal glucometers to biomimetic chips, Hidden in Plain Sight offers a wide-ranging survey of major breakthroughs in microfluidics during the last half century. At the same time, it is very much an internalist history, more concerned with the development of new microfluidic technologies than their political and cultural ramifications. For example, by highlighting how genetic evidence has exonerated the wrongly accused while ignoring debates concerning its reliability, Folch casts police departments’ embrace of DNA profiling as entirely beneficial.[2] He presents a similarly simplistic view of the home pregnancy test, casting it as an empowering example of paper-based microfluidics without contemplating the broader consequences of making women dependent on a single-use, disposable product to engage with their own fertility.[3]
While this internalism may frustrate some readers, Folch successfully reveals the pervasiveness of microfluidic technologies and sheds light on the interdisciplinary community that brought them to fruition. By encouraging scholars to focus more closely on the intersection of microelectronics and biotechnology, Hidden in Plain Sight sets the stage for future books and articles that will situate these developments within a broader social context.
Notes
[1]. Michael Riordan and Lillian Hoddeson, Crystal Fire: The Birth of the Information Age (New York: Norton, 1997), 254-56.
[2]. Jay D. Aronson, Genetic Witness: Science, Law, and Controversy in the Making of DNA Profiling (New Brunswick, NJ: Rutgers University Press, 2007).
[3]. Linda L. Layne, “Why the Home Pregnancy Test Isn’t the Feminist Technology It’s Cracked Up to Be and How to Make It Better,” in Feminist Technology, ed. Linda L. Layne, Sharra L. Vostral, and Kate Boyer (Urbana: University of Illinois Press, 2010), 89-118.
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Citation:
Benjamin Gross. Review of Folch, Albert, Hidden in Plain Sight: The History, Science, and Engineering of Microfluidic Technology.
H-Sci-Med-Tech, H-Net Reviews.
October, 2022.
URL: http://www.h-net.org/reviews/showrev.php?id=57939
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