Microscopic grippers used successfully in animal biopsies

Tiny, untethered microscale grippers have been successfully used to perform tissue biopsies in live animals, a study in the journal Gastroenterology reports. Researchers affiliated with the Johns Hopkins School of Medicine, Whiting School of Engineering and Institute for NanoBiotechnology developed the self-assembling microgrippers, called mu-grippers. The star-shaped devices use the animal’s own body heat to trigger them to clamp down around tissue to grab a sample like a tiny hand. Because the grippers are magnetic, they can later be retrieved for a minimally invasive procedure.

Dozens of dust-sized surgical mu- grippers in a vial. (Photo by  Evin Gultepe, Gracias Lab, Johns Hopkins University)

Dozens of dust-sized surgical mu- grippers in a vial. (Photo by Evin Gultepe, Gracias Lab, Johns Hopkins University)

David Gracias, the principal investigator for the study and associate professor of chemical and biomolecular engineering, was quoted in a Johns Hopkins press release about the work: “This is the first time that anyone has used a sub-millimeter-sized device — the size of a dust particle — to conduct a biopsy in a live animal … That’s a significant accomplishment. And because we can send the grippers in through natural orifices, it is an important advance in minimally invasive treatment and a step toward the ultimate goal of making surgical procedures noninvasive.”

Read more here.

 

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

 

 

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