UCLA bioengineers discover how particles self-assemble in flowing fluids

December 13, 2010

From atomic crystals to spiral galaxies, self-assembly is ubiquitous in nature. In biological processes, self-assembly at the molecular level is particularly prevalent.

Phospholipids, for example, will self-assemble into a bilayer to form a cell membrane, and actin, a protein that supports and shapes a cell's structure, continuously self-assembles and disassembles during cell movement.

Bioengineers at the UCLA Henry Samueli School of Engineering and Applied Science have been exploring a unique phenomenon whereby randomly dispersed microparticles self-assemble into a highly organized structure as they flow through microscale channels.

This self-assembly behavior was unexpected, the researchers said, for such a simple system containing only particles, fluid and a conduit through which these elements flow. The particles formed lattice-like structures due to a unique combination of hydrodynamic interactions.

The research, published online today in the journal Proceedings of the National Academy of Sciences, was led by UCLA postdoctoral scholar Wonhee Lee and UCLA assistant professor of bioengineering Dino Di Carlo.

The research team discovered the mechanism that leads to this self-assembly behavior through a series of careful experiments and numerical simulations. They found that continuous disturbance of the fluid induced by each flowing and rotating particle drives neighboring particles away, while migration of particles to localized streams due to the momentum of the fluid acts to stabilize the spacing between particles at a finite distance. In essence, the combination of repulsion and localization leads to an organized structure.

Once they understood the mechanism, the team developed microchannels that allowed for "tuning" of the spatial frequency of particles within an organized particle train. They found that by simply adding short regions of expanded channel width, the particles could be induced to self-assemble into different structures in a controllable and potentially programmable way.

"Programmable control of flowing microscale particles may be important in opening up new capabilities in biomedicine, materials synthesis and computation, similar to how improved control of flowing electrons has enabled a revolution in computing and communication," Di Carlo said.

For example, controlling the positions of microscale bioparticles, such as cells in flowing channels, is important for the operation of blood analysis and counting diagnostic systems. In addition, improving the uniformity of cell concentrations entering the microscale volume of a print head can enable burgeoning fields such as "tissue printing," in which single cells in a polymer ink are sequentially positioned to form a functional tissue architecture, such as the cylindrical lumen of a blood vessel.

More complete control of lattices of particles may also allow tunable manufacturing of optical or acoustic metamaterials that interact uniquely with light and sound waves based on the arrangement of the embedded particles, the researchers said.
-end-
The UCLA Henry Samueli School of Engineering and Applied Science, established in 1945, offers 28 academic and professional degree programs and has an enrollment of almost 5,000 students. The school's distinguished faculty are leading research to address many of the critical challenges of the 21st century, including renewable energy, clean water, health care, wireless sensing and networking, and cyber-security. Ranked among the top 10 engineering schools at public universities nationwide, UCLA Engineering is home to seven multimillion-dollar interdisciplinary research centers in wireless sensor systems, nanoelectronics, nanomedicine, renewable energy, customized computing, and the smart grid, all funded by federal and private agencies.

University of California - Los Angeles

Related Engineering Articles from Brightsurf:

Re-engineering antibodies for COVID-19
Catholic University of America researcher uses 'in silico' analysis to fast-track passive immunity

Next frontier in bacterial engineering
A new technique overcomes a serious hurdle in the field of bacterial design and engineering.

COVID-19 and the role of tissue engineering
Tissue engineering has a unique set of tools and technologies for developing preventive strategies, diagnostics, and treatments that can play an important role during the ongoing COVID-19 pandemic.

Engineering the meniscus
Damage to the meniscus is common, but there remains an unmet need for improved restorative therapies that can overcome poor healing in the avascular regions.

Artificially engineering the intestine
Short bowel syndrome is a debilitating condition with few treatment options, and these treatments have limited efficacy.

Reverse engineering the fireworks of life
An interdisciplinary team of Princeton researchers has successfully reverse engineered the components and sequence of events that lead to microtubule branching.

New method for engineering metabolic pathways
Two approaches provide a faster way to create enzymes and analyze their reactions, leading to the design of more complex molecules.

Engineering for high-speed devices
A research team from the University of Delaware has developed cutting-edge technology for photonics devices that could enable faster communications between phones and computers.

Breakthrough in blood vessel engineering
Growing functional blood vessel networks is no easy task. Previously, other groups have made networks that span millimeters in size.

Next-gen batteries possible with new engineering approach
Dramatically longer-lasting, faster-charging and safer lithium metal batteries may be possible, according to Penn State research, recently published in Nature Energy.

Read More: Engineering News and Engineering Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.