Science + Technology

UCLA Scientists Create Each Letter of the Alphabet at the Microscale; Research Could Lead to Tiny Devices

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UCLA scientists have designed and mass-produced billions offluorescent microscale particles in the shapes of all26 letters of the alphabet in an "alphabet soup" displaying "exquisite fidelityof the shapes."

The letters are made of solid polymeric materials dispersedin a liquid solution. The research will be published March 29 in the Journal ofPhysical Chemistry C, where it will be illustrated on the cover. The scientistsanticipate that their "LithoParticles" will havesignificant technological and scientific uses.

"We can even choose the font style; if we wanted Times NewRoman, we could produce that," said study co-author Thomas G. Mason, a UCLAassociate professor of chemistry who holds UCLA's John McTagueCareer Development Chair.

Lead author Carlos J. Hernandez, a UCLA chemistry graduatestudent, designed a customized font for the letters and produced them.

"We have demonstrated the power of a new method, at the microscale, to create objects of precisely designed shapesthat are highly uniform in size," said Mason, a member of UCLA's California NanoSystems Institute. "They are too small to see with theunaided eye, but with an optical microscope, you can see them clearly; theletters stand out in high fidelity. Our approach also works into the nanoscale."

Hernandez and Mason also have produced particles withdifferent geometric shapes, including triangles, crosses and doughnuts, as wellas three-dimensional "Janus particles," which have two differently shapedfaces.

"We have made fluorescent lithographic particles, we havemade complex three-dimensional shapes and, as shown by UCLA postdoctoral fellowKun Zhao, we can assemble these particles, for example, in a lock-and-keyrelationship," said Mason, whose research is at the intersection of chemistry,physics, engineering and biology. "We can mass-produce complex parts havingdifferent controlled shapes at a scale much smaller than scientists have beenable to produce previously. We have a high degree of control over the partsthat we make and are on the verge of making functional devices in solution. Wemay later be able to configure the parts into more complex and useful assemblies.

"How can we control and direct the assembly of tinycomponents to make a machine that works?" Mason asked. "Can we cause thecomponents to fit together in a controlled way that may be useful to us? Can wecreate useful complex structures out of fundamental parts, in solution, wherewe can mass-produce a small-scale engine, for example? We will pursue theseresearch questions."

Because each letter is smaller than many kinds of cells,possible applications include marking individual cells with particular letters.It may be possible, Mason said, to use a molecule to attach a letter to acell's surface or perhaps even insert a letter inside a cell and use theletter-marker to identify the cell. The research also could lead to thecreation of tiny pumps, motors or containers that could have medicalapplications, as well as security applications.

In addition to creating the letters, Mason's research groupcan pick up letters and reposition and reorient them in a microscaleversion of the game Scrabble (see image).

"We have used 'laser tweezers' to pick up the jumbledletters 'U, C, L, A' and move them together in order, like skywriting insolution," Mason said. UCLA chemistry graduate student James Wilking moved the letters to spell "UCLA."

Mason's research is funded in part by the National ScienceFoundation. He also receives research support from UCLA's John McTague Career Development Chair, which provides researchfunding for five years.

"UCLA's Office ofIntellectual Property has applied for patent protection on this platformtechnology and is beginning to speak with potential corporate partners to bringnew products to market based on this technology to benefit the public good,"said Earl Weinstein, who handles technology business development and licensingfor UCLA's technology transfer office.

As a graduate student at Princetonin the early 1990s, Mason founded a field called "thermal microrheology,"the techniques of which are now used by scientists worldwide. Microrheology is a method for examining the viscosity andelasticity of soft materials, including liquids, polymers and emulsions, on amicroscopic scale. Mason and Hernandez's research in the Journal of PhysicalChemistry C provides novel probes for microrheology.

For centuries, scientists and engineers have studied thedeformation and flow, or rheology, of soft materialson a large, laboratory scale. However, until Mason developed the field of microrheology, which relies on the random Brownian motionof probe particles, scientists had not done so on the microscopic level.

As with much cutting-edge science, Mason's research opens upthe possibility for developments that sound like science fiction. Are microscale devices that canactively identify cancer cells and eliminate them a real possibility? CouldMason's research help achieve this goal? The answer, he said, will probably notcome anytime soon, but perhaps in his lifetime. Understanding microrheology in synthetic materials is the first step tounderstanding what occurs in active materials like the interior of cells andmay help us understand how cells function while alive and how they die.

The Journal of Physical Chemistry C publishes research onnovel materials, nanoparticles and nanostructures.

For information about Mason's research, visit www.chem.ucla.edu/dept/Faculty/Mason.

About UCLA

California'slargest university, UCLA enrolls approximately 38,000 students per year andoffers degrees from the UCLA College of Letters and Science and 11 professionalschools in dozens of varied disciplines. UCLA consistently ranks among the topfive universities and colleges nationally in total research-and-developmentspending, receiving more than $820 million a year in competitively awardedfederal and state grants and contracts. For every $1 state taxpayers invest inUCLA, the university generates almost $9 in economic activity, resulting in anannual $6 billion economic impact on the Greater Los Angeles region. Theuniversity's health care network treats 450,000 patients per year. UCLA employsmore than 27,000 faculty and staff, has more than 350,000 living alumni and hasbeen home to five Nobel Prize recipients.

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