Rapid Fabrication of Complex 3D Extracellular Microenvironments by Dynamic Optical Projection Stereolithography

1. A. Ping Zhang^1,2,*, 
2. Xin Qu¹, 
3. Pranav Soman¹, 
4. Kolin C. Hribar¹, 
5. Jin W. Lee¹,
6. Shaochen Chen^1,*, 
7. Sailing He²

Article first published online: 12 JUL 2012

DOI: 10.1002/adma.201202024

The topographic features of the extracelluar matrix (ECM) lay the foundation for cellular behavior. A novel biofabrication method using a digital-mirror device (DMD), called dynamic optical projection stereolithography (DOPsL) is demonstrated. This robust and versatile platform can generate complex biomimetic scaffolds within seconds. Such 3D scaffolds have promising potentials for studying cell interactions with microenvironments in vitro and in viv

Bond-Order Discrimination by Atomic Force Microscopy

Science 14 September 2012: 
Vol. 337 no. 6100 pp. 1326-1329 
DOI: 10.1126/science.1225621

1. Leo Gross¹,*, 
2. Fabian Mohn¹, 
3. Nikolaj Moll¹, 
4. Bruno Schuler¹, 
5. Alejandro Criado², 
6. Enrique Guitián²,
7. Diego Peña², 
8. André Gourdon³, 
9. Gerhard Meyer¹

We show that the different bond orders of individual carbon-carbon bonds in polycyclic aromatic hydrocarbons and fullerenes can be distinguished by noncontact atomic force microscopy (AFM) with a carbon monoxide (CO)–functionalized tip. We found two different contrast mechanisms, which were corroborated by density functional theory calculations: The greater electron density in bonds of higher bond order led to a stronger Pauli repulsion, which enhanced the brightness of these bonds in high-resolution AFM images. The apparent bond length in the AFM images decreased with increasing bond order because of tilting of the CO molecule at the tip apex

How Cucumber Tendrils Curl

L. Mahadevan et alScience 31 August 2012: 
Vol. 337 no. 6098 pp. 1087-1091 
DOI: 10.1126/science.1223304

The helical coiling of plant tendrils has fascinated scientists for centuries, yet the underlying mechanism remains elusive. Moreover, despite Darwin’s widely accepted interpretation of coiled tendrils as soft springs, their mechanical behavior remains unknown. Our experiments on cucumber tendrils demonstrate that tendril coiling occurs via asymmetric contraction of an internal fiber ribbon of specialized cells. Under tension, both extracted fiber ribbons and old tendrils exhibit twistless overwinding rather than unwinding, with an initially soft response followed by strong strain-stiffening at large extensions. We explain this behavior using physical models of prestrained rubber strips, geometric arguments, and mathematical models of elastic filaments. Collectively, our study illuminates the origin of tendril coiling, quantifies Darwin’s original proposal, and suggests designs for biomimetic twistless springs with tunable mechanical responses.

Robotic Tentacles with Three-Dimensional Mobility Based on Flexible Elastomers

1. Ramses V. Martinez¹,
2. Jamie L. Branch¹,
3. Carina R. Fish¹,
4. Lihua Jin⁴,
5. Robert F. Shepherd¹,
6. Rui M. D. Nunes¹,
7. Zhigang Suo^2,4,
8. George M. Whitesides^1,2,3,*

Article first published online: 7 SEP 2012

DOI: 10.1002/adma.201203002

 

 

Soft robotic tentacles that move in three dimensions upon pressurization are fabricated by composing flexible elastomers with different tensile strengths using soft lithographic molding. These actuators are able to grip complex shapes and manipulate delicate objects. Embedding functional components into these actuators (for example, a needle for delivering fluid, a video camera, and a suction cup) extends their capabilities.

A Synthetic Chemomechanical Machine Driven by Ligand–Receptor Bonding

Gabriel J. Lavella *, Amol D. Jadhav , and Michel M. Maharbiz

^† Department of Electrical Engineering and Computer Science, University of California, Berkeley, California 94720, United States

Nano Lett., Article ASAP

DOI: 10.1021/nl3026136

Publication Date (Web): August 27, 2012

Copyright © 2012 American Chemical Society

 

 

 The ability to create synthetic chemomechanical machines with engineered functionality promises large technological rewards. However, current efforts in molecular chemistry are restrained by the formidable challenges faced in molecular structure and function prediction. An alternative approach to engineering machines with tailorable chemomechanical functionality is to design Brownian ratchet devices using molecular assemblies. We demonstrate this through the creation of autonomous molecular machines that sense, mechanically react, and extract energy from ligand–receptor binding. We present a specific instantiation, measuring approximately 100 nm in length, which actuates upon detection of a streptavidin ligand. Machines were designed through the tailoring of energy landscapes on 3D DNA origami motifs. We also analyzed the response over a logarithmic concentration ratio (device:ligand) range from 1:10¹ to 1:10⁵.

Polymersomes Containing a Hydrogel Network for High Stability and Controlled Release

1. Shin-Hyun Kim^1,2,*,
2. Jin Woong Kim³,
3. Do-Hoon Kim⁴,
4. Sang-Hoon Han⁴,
5. David A. Weitz^1,*

Article first published online: 7 SEP 2012

DOI: 10.1002/smll.201201709

 Capillary microfluidic devices are used to prepare monodisperse polymersomes consisting of a hydrogel core and a bilayer membrane of amphiphilic diblock-copolymers. To make polymersomes, water-in-oil-in-water double-emulsion drops are prepared as templates through single-step emulsification in a capillary microfluidic device. The amphiphile-laden middle oil phase of the double-emulsion drop dewets from the surface of the innermost water drop, which contains hydrogel prepolymers; this dewetting leads to the formation of a bilayer membrane. Subsequently, the oil phase completely separates from the innermost water drop, leaving a polymersome. Upon UV illumination of the polymersome, the prepolymers encapsulated within the interior are crosslinked, forming a hydrogel core. The hydrogel network within the polymersomes facilitates sustained release of the encapsulated materials and increases the stability of the polymersomes through the formation of a scaffold to support the bilayer. In addition, this approach provides a facile method to make monodisperse hydrogel particles directly dispersed in water.

A Mechanically Controlled Indicator Displacement Assay

1. Dr. Keita Sakakibara^1,2,
2. Leo A. Joyce³,
3. Dr. Taizo Mori^1,2,
4. Takuya Fujisawa¹,
5. Dr. Shagufta H. Shabbir³,
6. Dr. Jonathan P. Hill^1,2,
7. Prof. Eric V. Anslyn^3,*,
8. Prof. Katsuhiko Ariga^1,2,*

Article first published online: 29 AUG 2012

DOI: 10.1002/anie.201203402

 Push a host: Mechanical compression was applied to a host monolayer at an interface, which facilitated an indicator displacement assay. The fluorescence resonance energy transfer (FRET) between the host and indicator was switched on by this compression. Addition of D-glucose caused the indicator to be displaced, effectively quenching the FRET process.