The Microfluidics Lab: Enabler of Experimentation


Wednesday, July 13, 2022

The Microfluidics Lab (MFL) at UC Santa Barbara is one of the few campus labs where relatively little research is conducted. It is, rather, an enabling lab, where researchers and lab staff fabricate tools required for their experiments. Established in its current location in Elings Hall ten years ago, the lab began life closely aligned with semiconductor research, according to longtime manager, Dave Bothman, who has spent 36 years at UCSB and who, though officially retired, continues to work part-time in the MFL, which gets its name from the word for the easily described process of microfluidics, which Bothman says, is “simply making devices that have really small channels for fluids to flow through.”

The Microfluidics Lab came to be in a rather roundabout way. UCSB has a long history of semiconductor manufacturing, and in the late 1990s and early 2000s, Bothman explains, that work expanded into making microelectromechanical systems (MEMS), which are mechanical devices made with the same tools developed to manufacture semiconductors. “Eventually, some of those MEMS researchers started moving into microfluidics,” explains Bothman, who began his career as a professional “tinkerer” while working in a machine shop as a UC Santa Cruz undergraduate. He then transferred to Scripps Institute, where he spent seven years building experiments and equipment for ocean research. He was hired by the Department of Mechanical Engineering at UCSB in 1986. “I feel really grateful that I’ve been able to advance my career and continue to work with my hands,” he says.

Bothman’s successor as MFL manager, Brian Dincau, says that he looks forward to “playing a key role in the future development of the lab and training students to make experimental devices similar to what I’ve made for my own research. I’m excited to support other research groups that have an idea of what they want to measure or what sort of experiment they want to run but might not yet know how to build what they need.”

He also says that he and his predecessor have a lot of similarities: “We both like to tinker, we both like to talk about relatively technical things, and we both really value the duality of the lab — that it serves the university’s dual goals of furthering research by helping people to invent and create while providing students with a world-class training and learning environment. I think education is one of the most important means of enacting change for the good, and I really want to be a part of that.”

In the early days of microfluidics, Bothman says, everyone who was making them was a cleanroom user, but a cleanroom is not an easy lab to get started in. There is a start-up fee, and it takes about six months to learn to use all the tools and work in it safely. No undergraduates are allowed in, and graduate students have to take a prerequisite class before entering. Most microfluidics work, however, either does not require a cleanroom or require it for only a small part of the process.

Eventually, with researchers from other departments finding uses for MF devices, an informal word-of-mouth supply process developed that made it possible for interested researchers to obtain a device they needed from someone who had access to a cleanroom — but in nothing that could be considered a timely manner.

Recognizing the bottleneck, Bothman suggested to administrators in the California NanoSystems Institute (CNSI) at UCSB that they build an MF lab in Elings Hall. “They had already been thinking about that and were enthusiastic, and so we built this lab,” Bothman says. “The intention from the very beginning was that users from all over campus could come and make MF devices.”

That intention was sound, as the process of moving fluids through very small channels, which can range in diameter from about seventy microns (the approximate width of a human hair), up to about one millimeter and even, occasionally, larger, is called for in widely varied research and an array of disciplines. In fact, before COVID, the lab had about two hundred users, and in midpandemic, in 2021, people from more than forty different research groups used it. It attracts everyone from physicists who might be studying the physics of droplet formation to chemists who might want to mix reagents in extremely small volumes,” Bothman says.

Mechanical engineering professor and CNSI co-director Megan Valentine, who is co-director of the California NanoSystems Institute, which supports and houses the Microfluidics Laboratory, says that the MFL “has been a tremendous resource for a number of projects in my experimental research group; everyone in my group uses this facility, from undergrads just starting on their first project to seasoned researchers who are independently driving multiple projects. Dave Bothman has provided important training and oversight, while encouraging researchers to explore new designs and test new ideas.”

Valentine says that researchers in her group have often used the lab’s 3D printing capabilities to generate low-cost, customized devices that can apply rapid forces to cells during imaging, as well as microfluidic devices capable of rapid fluidic mixing or generation of microscale droplets. “These devices are then used to understand and control the mechanical properties of cells in order to create improved diagnostics and therapeutics,” she says. “The tools and guidance provided by the MFL were essential for this work.”

Emilie Dressaire, an assistant professor in mechanical engineering whose research is aimed at developing bio-inspired strategies to control and sense fluid flows at small scales — work that combines fluid dynamics, soft matter, and biology — says that her group uses the lab to make MF devices, which are then used to make emulsions and droplets. “We’re hoping to use those emulsions to stabilize structures,” she says, adding, “We’ve been using all the lab’s PDMS tools [PDMS, or polydimethyl siloxane, being the most widely used silicon-based organic polymer]. We use the 3D printer to make molds, and we use the molds to create surfaces having a “hairlike” texture similar to that of cilia.”

Paul J. Atzberger, a professor in Mechanical Engineering and Mathematics, has made use of the MFL for multiple collaborative interdisciplinary projects. They have involved modeling particle and polymer transport phenomena within fluidic devices, and related experiments; developing novel approaches for modeling and simulating transport phenomena associated with device electrostatics and electrokinetics; and investigating the roles of phenomena such as discrete ion-ion correlation effects in transport within microfluidic devices.

One of the ways people most frequently use the lab is to make what are called droplet generation chips. And, Bothman explains, one of the most common ways to make the chips is to cast liquid silicon onto a silicon wafer that has some raised sections, creating a liquid silicon cast on top of a mold. Peeling the mold off leaves channels embossed onto the silicon. That piece of silicon can then be bonded to a glass slide that has inlets and outlets, or has holes punched in it to serve as inlets and outlets, and can then be put under a microscope so that the fl ow can be observed.

Not all chips made in the lab are used for generating droplets. Some are employed to breed bacteria, while others are intended to encapsulate bacteria inside a droplet of nutrient so that the bacteria can be observed as it evolves on the chip. Still other chips are applied in processes that use electro-chemistry to detect disease.

In addition to the many and varied researchers who fabricate devices in the lab, another group of people come to use a unique microscope — the Keyence VHX 5000 — which, Bothman says, “can do things that no other microscope on campus can.”

While many other microscopes can magnify up to a thousand times, as the VHX 5000 can, that level of resolution typically yields a very shallow depth of field. But this scope has a function that allows it to take multiple scans and combine them to provide perfect focus across a much greater depth of fi eld, ranging from ten times to a thousand times resolution. “It also takes really good photos and has excellent measuring capabilities,” Bothman says.

For her doctoral work, which built upon a decade-long chain of research at UCSB, Marcela Areyano (PhD ‘21) used the microscope to measure the diameter of the elastic threads that enable mussels to adhere to wet surfaces. Areyano’s measurements allowed her, in turn, to calculate the area of the threads and get meaningful measurements of their mechanical properties. “Any chance I got, I tried to use that microscope,” she says.

Areyano also made equipment in the lab for testing research setups to look at how mechanics and physical structures affect the performance of millimeter-scale synthetic adhesive structures modeled after adhesive mussel strings. For that, she laser-etched marker guides onto glass slides to ensure that her samples would be correctly placed and her readings, therefore, consistent; used the 3D printer to make molds to form the structures, and used the lab’s ovens to cure the resulting synthetic structures, which resembled mussel threads.

Many tasks, many tools, one busy place, and a microscope that is powerful but, more importantly, versatile: fitting for the diversely empowering Microfluidics Lab.

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