Cambridge, MA, United States
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Hancock M.J.,Harvard University | Yanagawa F.,Harvard University | Jang Y.-H.,Harvard University | He J.,Harvard University | And 7 more authors.
Small | Year: 2012

A simple technique is presented for controlling the shapes of micro- and nanodrops by patterning surfaces with special hydrophilic regions surrounded by hydrophobic boundaries. Finite element method simulations link the shape of the hydrophilic regions to that of the droplets. Shaped droplets are used to controllably pattern planar surfaces and microwell arrays with microparticles and cells at the micro- and macroscales. Droplets containing suspended sedimenting particles, initially at uniform concentration, deposit more particles under deeper regions than under shallow regions. The resulting surface concentration is thus proportional to the local fluid depth and agrees well with the measured and simulated droplet profiles. A second application is also highlighted in which shaped droplets of prepolymer solution are crosslinked to synthesize microgels with tailored 3D geometry. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Zamanian B.,Harvard University | Masaeli M.,Northeastern University | Nichol J.W.,Harvard University | Khabiry M.,Harvard-MIT Division of Health Sciences and Technology | And 3 more authors.
Small | Year: 2010

Centimeter-scale cell-laden hydrogel sheets are created by the directed assembly of shape-controlled microgels followed by UV polymerization. A hierarchical assembly technique creates complex multigel building blocks, which are then assembled into gel sheets with precise spatial control over the cell distribution. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Hancock M.J.,Harvard University | He J.,Xi'an Jiaotong University | Mano J.F.,European Institute of Excellence on Tissue Engineering and Regenerative Medicine | Mano J.F.,IBB Institute for Biotechnology And Bioengineering | And 4 more authors.
Small | Year: 2011

A simple and inexpensive method is presented employing passive mechanisms to generate centimeters-long gradients of molecules and particles in under a second with only a coated glass slide and a micropipette. A drop of solution is pipetted onto a fluid stripe held in place on a glass slide by a hydrophobic boundary. The resulting difference in curvature pressure drives the flow and creates a concentration gradient by convection. Experiments and theoretical models characterize the flows and gradient profiles and their dependence on the fluid volumes, properties, and stripe geometry. A bench-top rapid prototyping method is outlined to allow the user to design and fabricate the coated slides using only tape and hydrophobic spray. The rapid prototyping method is compatible with microwell arrays, allowing soluble gradients to be applied to cells in shear-protected microwells. The method's simplicity makes it accessible to virtually any researcher or student and its use of passive mechanisms makes it ideal for field use and compatible with point-of-care and global health initiatives. A drop of solution is pipetted onto a fluid stripe held in place on a glass slide by a hydrophobic boundary. The resulting difference in curvature pressure drives the flow and creates a centimeters-long concentration gradient in under a second by convection. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nikkhah M.,Harvard University | Nikkhah M.,Harvard-MIT Division of Health Sciences and Technology | Nikkhah M.,Partners Research Building | Edalat F.,Harvard University | And 8 more authors.
Biomaterials | Year: 2012

Cells in their in vivo microenvironment constantly encounter and respond to a multitude of signals. While the role of biochemical signals has long been appreciated, the importance of biophysical signals has only recently been investigated. Biophysical cues are presented in different forms including topography and mechanical stiffness imparted by the extracellular matrix and adjoining cells. Microfabrication technologies have allowed for the generation of biomaterials with microscale topographies to study the effect of biophysical cues on cellular function at the cell-substrate interface. Topographies of different geometries and with varying microscale dimensions have been used to better understand cell adhesion, migration, and differentiation at the cellular and sub-cellular scales. Furthermore, quantification of cell-generated forces has been illustrated with micropillar topographies to shed light on the process of mechanotransduction. In this review, we highlight recent advances made in these areas and how they have been utilized for neural, cardiac, and musculoskeletal tissue engineering application. © 2012 Elsevier Ltd.

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