preparation-high-temperature-anti-adhesion-behavior-slippery-surface

Preparation and High-temperature Anti-adhesion Behavior of a Slippery Surface on Stainless Steel

Anti-adhesion surfaces with high-temperature resistance have a wide application potential in electrosurgical instruments, engines, and pipelines. A ...

Beihang University

Soft tissue damage is often at risk during the use of a surgical grasper, because of the strong holding force required to prevent slipping of the soft tissue in wet surgical environments. Improvement of wet friction properties at the interface between the surgical grasper and soft tissue can greatly reduce the holding force required and, thus, the soft tissue damage. To design and fabricate a biomimetic microscale surface with strong wet friction, the wet attachment mechanism of tree frog toe pads was investigated by observing their epithelial cell structure and the directionally dependent friction on their toe pads. Using these observations as inspiration, novel surface micropatterns were proposed for the surface of surgical graspers. The wet friction of biomimetic surfaces with various types of polygon pillar patterns involving quadrangular pillars, triangular pillars, rhomboid pillars, and varied hexagonal pillars were tested. The hexagonal pillar pattern exhibited improved wet frictional performance over the modern surgical grasper jaw pattern, which has conventional macroscale teeth. Moreover, the deformation of soft tissue in the bioinspired surgical grasper with a hexagonal pillar pattern is decreased, compared with the conventional surgical grasper.

Bioinspired Surface for Surgical Graspers Based on the Strong Wet Friction of Tree Frog Toe Pads.

Recent interest in high-precision positioning stages with large travel ranges has sparked renewed attention to the development of voice coil motors (VCMs). Due to their large output force, VCMs can actuate more complicated flexure structures, eliminate rail friction, and improve positioning speed. The VCM structure is both compact and flexible; hence, it is convenient to design VCMs for a variety of stage structures. Furthermore, VCMs combined with other actuators are able to achieve large travel ranges with high precision. In this paper, we summarize the principles and control methods of a typical VCM, and we analyze its properties, including thrust force, acceleration, and response time. We then present recent research on high-precision VCM positioning stages with large travel ranges.

Contributed Review: Application of voice coil motors in high-precision positioning stages with large travel ranges.

Numerous natural systems contain surfaces or threads that enable directional water transport. This behaviour is usually ascribed to hierarchical structural features at the microscale and nanoscale, with gradients in surface energy and gradients in Laplace pressure thought to be the main driving forces. Here we study the prey-trapping pitcher organs of the carnivorous plant Nepenthes alata. We find that continuous, directional water transport occurs on the surface of the 'peristome'--the rim of the pitcher--because of its multiscale structure, which optimizes and enhances capillary rise in the transport direction, and prevents backflow by pinning in place any water front that is moving in the reverse direction. This results not only in unidirectional flow despite the absence of any surface-energy gradient, but also in a transport speed that is much higher than previously thought. We anticipate that the basic 'design' principles underlying this behaviour could be used to develop artificial fluid-transport systems with practical applications.

Continuous directional water transport on the peristome surface of Nepenthes alata.

A novel unidirectional liquid spreading surface with an inclined arc pitted groove, inspired by the continuous unidirectional liquid spreading mechanism on the peristome surface of N. alata, is explored and fabricated by two-step UV lithography. Its superior unidirectional liquid spreading capability to that of other surface patterns is demonstrated, and its unidirectional liquid spreading mechanism is investigated.

A Novel Bioinspired Continuous Unidirectional Liquid Spreading Surface Structure from the Peristome Surface of Nepenthes alata.

Unidirectional liquid spreading without energy input has attracted considerable attention due to various potential applications such as biofluidics devices and self-lubrication. Introducing a surface wettable gradient or asymmetric nanostructures onto the surface has successfully harnessed the liquid to spread unidirectionally. However, these surfaces are still plagued with problems that restrict their practical applications: fixed spreading state for a fixed surface, and spreading slowly over a short distance. Herein, bioinspired from the fast continuous unidirectional water transport on the peristome of Nepenthes alata, we report a smart peristome with temperature-controlled unidirectional water spreading. The smart artificial peristome was fabricated by grafting the thermoresponsive material PNIPAAm onto the artificial PDMS peristome. Unidirectional water spreading on the smart peristome can be dynamically regulated by changing the surface temperature. Besides, the water spreading is demonstrated with a remarkable reversibility and stability. By investigating the relationship between liquid spreading distance and wettability, the underlying mechanism was revealed. This work gives a new way to achieve the control of unidirectional liquid spreading available for controllable microfluidics and medical devices.

Bioinspired Smart Peristome Surface for Temperature-Controlled Unidirectional Water Spreading.

The slippery peristome of the pitcher plant Nepenthes has attracted much attention due to its unique function for preying on insects. Recent findings on the peristome surface of Nepenthes alata demonstrate a fast and continuous unidirectional liquid transport, which is enabled by the combination of a pinning effect at the sharp edges and a capillary rise in the wedge, deriving from the multiscale structure, which provides inspiration for designing and fabricating functional surfaces for unidirectional liquid transport. Developments in the fabrication methods of peristome-inspired surfaces and control methods for liquid transport are summarized. Both potential applications in the fields of microfluidic devices, biomedicine, and mechanical engineering and directions for further research in the future are discussed.

Liwen Zhang

School of Mechanical Engineering and Automation

Beihang University

Preparation and High-temperature Anti-adhesion Behavior of a Slippery Surface on Stainless Steel