Complex three-dimensional high aspect ratio microfluidic network manufactured in combined PerMX dry-resist and SU-8 technology

In this paper we present a new fabrication method that combines for the first time popular SU-8 technology and PerMX dry-photoresist lamination for the manufacturing of high aspect ratio three-dimensional multi-level microfluidic networks. The potential of this approach, which further benefits from wafer-level manufacturing and accurate alignment of fluidic levels, is demonstrated by a highly integrated three-level microfluidic chip. The hereby achieved network complexity, including 24 fluidic vias and 16 crossing points of three individual microchannels on less than 13 mm(2) chip area, is unique for SU-8 based fluidic networks. We further report on excellent process compatibility between SU-8 and PerMX dry-photoresist which results in high interlayer adhesion strength. The tight pressure sealing of a fluidic channel (0.5 MPa for 1 h) is demonstrated for 150 μm narrow SU-8/PerMX bonding interfaces.     

论问题解决与教学促进

大多数教育工作者都认为问题解决很重要,但是他们对什么是问题解决持有不同观点,在怎样教给学生问题解决的本领上也没有达成一致意见。各种不同观点主要集中于将问题解决视为教育目标、教育方法以及技能训练之间的差异问题上。其一,目标型问题解决不应只限于良构问题解决,而应该延伸到现实问题解决;其二,对初学者来说,方法型问题解决有其明显的局限性,给予这些学习者足够帮助,对于培养他们的问题解决能力具有重要作用;其三,技能型问题解决不应被看作是只在培养专长过程的初期才会出现,而应被视为在系统1模式与系统2模式中平行发展的一个过程。总结以上观点,综合学习设计模式完全可以用来促进此三种类型的问题解决,并其本回答了问题解决最好应该怎样教的问题。     

Low cost fabrication and assembly process for re-usable 3D polydimethylsiloxane (PDMS) microfluidic networks

A method to easily manufacture and assemble a polydimethylsiloxane (PDMS) based microfluidic device is described. The method uses low cost materials and re-usable laser cut polymethyl methacrylate (PMMA) parts. In addition, the thickness of PDMS layers can be controlled and both PDMS layer surfaces are flat, which allows for multi-layer PDMS structures to be assembled. The use of mechanical clamping to seal the structure allows for easy cleaning and re-use of the manufactured part as it can be taken apart at any time. In this way, selected layers can be re-used or replaced. The process described can be easily adopted and utilised without the need for any costly clean room facilities or equipment such as oxygen bonders, making it ideal for laboratories, universities, and classrooms exploring microfluidics applications.     

R Tricks for Kids

Real‐world phenomena simulation models, which can be used to engage middle‐school students with probability, are described. Links to R instructional material and easy‐to‐use code are provided to facilitate implementation in the classroom.     

Microfluidic channel structures speed up mixing of multiple emulsions by a factor of ten

We present a novel use for channel structures in microfluidic devices, whereby two two-phase emulsions, one created on-chip, the other off-chip, are rapidly mixed with each other in order to allow for the coalescence of one emulsion with the other. This approach has been motivated by the difficulty in introducing aqueous cross linking agents into droplets by utilising conventional approaches. These conventional approaches include continuous introduction of the different aqueous reagents before droplet formation or alternatively formation of individual droplets of each reagent and subsequent droplet merging later in the microfluidic device. We show that our approach can decrease the mixing time for these fluidic systems by a factor greater than 10 times when compared to a standard microfluidic channel without structures, thereby also allowing for additional reaction time within the microfluidic device. This method shows an application for microfluidic channel structures not before demonstrated, also demonstrating an alternative method for introducing reagents such as cross linkers which link polymer chains to form particles, and provides an example where enzymes are immobilized in monodisperse particles.     

Knowledge is power: Issues of measuring training and performance in cycling

ABSTRACT

Mobile power meters provide a valid means of measuring cyclists’ power output in the field. These field measurements can be performed with very good accuracy and reliability making the power meter a useful tool for monitoring and evaluating training and race demands. This review presents power meter data from a Grand Tour cyclist’s training and racing and explores the inherent complications created by its stochastic nature. Simple summary methods cannot reflect a session’s variable distribution of power output or indicate its likely metabolic stress. Binning power output data, into training zones for example, provides information on the detail but not the length of efforts within a session. An alternative approach is to track changes in cyclists’ modelled training and racing performances. Both critical power and record power profiles have been used for monitoring training-induced changes in this manner. Due to the inadequacy of current methods, the review highlights the need for new methods to be established which quantify the effects of training loads and models their implications for performance.