Engineers put a new ‘twist’ on lab-on-a-chip

Close-up of a cylindrically-shaped microfluidic device with two fluorescent solutions flowing through. Reproduced with permission from Nature Communications.

A leaf works something like a miniature laboratory. While the pores on the leaf surface allow it to channel nutrients in and waste products away from a plant, part of a leaf’s function also lies in its ability to curl and twist. Engineers use polymers to create their own mini-labs, devices called “labs-on-a-chip,” which have numerous applications in science, engineering and medicine. The typical flat, lab on a chip, or microfluidic device, resembles an etched microscopy cover slip with channels and grooves.

But what if you could get that flat lab-on-a-chip to self-assemble into a curve, mimicking the curl, twist or spiral of a leaf? Mustapha Jamal, a PhD student and IGERT fellow from Johns Hopkins Institute for NanoBioTechnology, has created a way to make that so.

Jamal is the lead author on “Differentially photo-crosslinked polymers enable self-assembling microfluidics,” published November 8, 2011 in Nature Communications. Along with principle investigator David Gracias, associate professor of Chemical and Biomolecular Engineering in the Whiting School of Engineering, and fellow graduate student Aasiyeh Zarafshar, Jamal has developed, for the first time, a method for creating three-dimensional lab-on-a-chip devices that can curl and twist.

The process involves shining ultraviolet (UV) light on a film of a substance called SU-8. Film areas closer to the light source become more heavily crosslinked than layers beneath, which on solvent conditioning creates a stress gradient.

Immersing the film in water causes the film to curl. Immersion in organic solvents like acetone causes the film to flatten. The curling and flattening can be reversed. The result, Jamal said, is the “self-assembly of intricate 3D devices that contain microfluidic channels.” This simple method, he added, can “program 2D polymeric (SU-8) films such that they spontaneously and reversibly curve into intricate 3D geometries including cylinders, cubes and corrugated sheets.”

Members of the Gracias lab have previously created curving and folding polymeric films consisting of two different materials. This new method achieves a stress gradient along the thickness of a single substance. “This provides considerable flexibility in the type and extent of curvature that can be created by varying the intensity and direction of exposure to UV light,” Gracias said.

Gracias explained that the method works with current protocols and materials for fabricating flat microfluidic devices. For example, one can design a 2D film with one type of lab-on-a-chip network, and then use their method to shape it into another geometry, also with microfluidic properties.

Fluorescent image of curved, self-assembled microfluidic device. Reproduced with permission from Nature Communications.

“Since our approach is compatible with planar lithography methods, we can also incorporate optical elements such as split ring resonators that have unique optical features. Alternatively, flexible electronic circuits could be incorporated and channels could be used to transport cooling fluids” Gracias said.

Tissue engineering is among the many important applications for 3D microfluidic devices, Gracias said. “Since many hydrogels can be photopolymerized, we can use the methodology of differential cross-linking to create stress gradients in these materials,” Gracias explained. “We plan to create biodegradable, vascularized tissue scaffolds using this approach.”

Link to the journal article here.

Story by Mary Spiro

 

 

JHU Applied Physics Lab hosting 2nd Annual Nanomaterials Symposium

The Johns Hopkins Applied Physics Laboratory will host its 2nd Annual Nanomaterials Symposium on Monday, March 14 from 8:30 a.m. to 5 p.m. in the Kossiakoff Conference and Education Center, 11100 Johns Hopkins Road, Laurel, Md. 20723-6099. Come hear stimulating talks and network with speakers, attendees, and
sponsor panelists. Includes a special session for students on postdoctoraal and internship opportunities. Submit a poster for the poster session.

The symposium is FREE for students, but $25 for all others, and lunch is included.

Deadline to register is 5 p.m. March 8. Register online here.

Invited speakers include:

  • Jonah Erlebacher, Johns Hopkins University/INBT
  • Jason Benkoski, JHU Applied Physics Laboratory/INBT
  • Lourdes Salamanca-Riba, University of Maryland College Park
  • Hai-Quan Mao, Johns Hopkins University/INBT
  • Theodosia Gougousi, University of Maryland Balitmore County
  • Gary Rubloff, University of Maryland College Park
  • Brian Holloway, Defense Advanced Research Projects Agency

For additional information:

Johns Hopkins Applied Physics Lab

240-228-9166

Animator, scientist partner to illustrate cover of Advanced Materials

AM_3_U1resizeThe cover of the January 19, 2010 issue of the journal Advanced Materials features a photo illustration executed by Martin Rietveld, web director and animator at Johns Hopkins Institute for NanoBioTechnology. Rietveld’s work illustrates an article about chemomechanical actuators—grippers that open and close like a hand in response to chemical reactions. The paper is based on the research of lead author, doctoral student Jatinder Randhawa in the laboratory of David Gracias, associate professor of chemical and biomolecular engineering and faculty affiliate of the Institute for Nanobiotechnology. Randhawa conceptualized the illustration of his research for the journal cover.

Says Gracias, “Chemomechanical actuation is intellectually appealing since it is widely observed in nature, but chemomechanical actuation is relatively unexplored in human engineering where the dominant strategy to actuate structures is based on electromechanical actuation (i.e. with electrical signals). Here, microstructures open and close reversibly in response to chemical surface oxidation and reduction without the need for any wires or batteries.”

Related links:

Chemomechanical Actuators: Reversible Actuation of Microstructures by Surface-Chemical Modification of Thin-Film Bilayers. Jatinder S. Randhawa, Michael D. Keung, Pawan Tyagi, David H. Gracias.

Johns Hopkins Institute for NanoBioTechnology Animation Studio

David Gracias INBT Faculty Profile

Environmental, health impacts of engineered nanomaterials theme of INBT’s annual symposium

By 2015, the National Science Foundation reports that the nanotechnology industry could be worth as much as $1 trillion. Nanomaterials have many beneficial applications for industry, medicine and basic scientific research. However, because nanomaterials are just a few atoms in size, they also may pose potential risks for human health and the environment.

Cross-sectional autoradiograms of rodent brains showing (A) control physiological state; and (B) and (C) showing distribution of brain injury from an injected neurotoxicant. Red areas indicate the highest concentrations of a biomarker that identifies brain areas that are damaged by the neurotoxicant. (Guilarte Lab/JHU)

Cross-sectional autoradiograms of rodent brains showing (A) control physiological state; and (B) and (C) showing distribution of brain injury from an injected neurotoxicant. Red areas indicate the highest concentrations of a biomarker that identifies brain areas that are damaged by the neurotoxicant. (Guilarte Lab/JHU)

To increase awareness of Hopkins’ research in this emerging area of investigation, the theme for the fourth annual symposium hosted by Johns Hopkins Institute for NanoBioTechnology (INBT) will be environmental and health impacts of engineered nanomaterials. INBT’s symposium will be held Thursday, April 29, from 8 a.m. to 3 p.m. at the university’s Bloomberg School of Public Health in Baltimore, Md.

Morning talks in Sheldon Hall by eight Hopkins faculty experts will discuss neurotoxicity, exposure assessment, manufacture and characterization of nanomaterials, policy implications and many other topics. In the afternoon, a poster session will be held in Feinstone Hall featuring nanobiotechnology research from across the university’s divisions.

INBT is seeking corporate sponsorships for the symposium. Interested parties should contact Thomas Fekete, INBT’s director of corporate partnerships at tmfeke@jhu.edu or 410-516-8891.

Media inquiries should be directed to Mary Spiro, INBT’s science writer and media relations director, at mspiro@jhu.edu or 410-516-4802.

A call for posters announcement will be made at a later date.

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