抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Soft lithography is an alternative to silicon-based micromachining that uses replica molding of nontraditional elastomeric materials to fabricate stamps and microfluidic channels. We describe here an extension to the soft lithography paradigm, multilayer soft lithography, with which devices consisting of multiple layers may be fabricated from soft materials. We used this technique to build active microfluidic systems containing on-off valves, switching valves, and pumps entirely out of elastomer. The softness of these materials allows the device areas to be reduced by more than two orders of magnitude compared with silicon-based devices. The other advantages of soft lithography, such as rapid prototyping, ease of fabrication, and biocompatibility, are retained.

http://science.sciencemag.org/content/sci/288/5463/113.full.pdf

Monolithic microfabricated valves and pumps by multilayer soft lithography

The American Society for Testing and Materials (ASTM) is an independent organization devoted to the development of standards.

American Society for Testing and Materials

Hydrogel: Preparation, characterization, and applications: A review

Hydrophilic polymers are the center of research emphasis in nanotechnology because of their perceived “intelligence”. They can be used as thin films, scaffolds, or nanoparticles in a wide range of biomedical and biological applications. Here we highlight recent developments in engineering uncrosslinked and crosslinked hydrophilic polymers for these applications. Natural, biohybrid, and synthetic hydrophilic polymers and hydrogels are analyzed and their thermodynamic responses are discussed. In addition, examples of the use of hydrogels for various therapeutic applications are given. We show how such systems’ intelligent behavior can be used in sensors, microarrays, and imaging. Finally, we outline challenges for the future in integrating hydrogels into biomedical applications.

/pdf/hydrogels-in-biology-and-medicine-from-molecular-principles-3lowrzjjsl.pdf

Hydrogels in Biology and Medicine: From Molecular Principles to Bionanotechnology†

Many scientific papers have been written concerning gas sensors for different sensor applications using several sensing principles. This review focuses on sensors and sensor systems for gaseous ammonia. Apart from its natural origin, there are many sources of ammonia, like the chemical industry or intensive life-stock. The survey that we present here treats different application areas for ammonia sensors or measurement systems and different techniques available for making selective ammonia sensing devices. When very low concentrations are to be measured, e.g. less than 2 ppb for environmental monitoring and 50 ppb for diagnostic breath analysis, solid-state ammonia sensors are not sensitive enough. In addition, they lack the required selectivity to other gasses that are often available in much higher concentrations. Optical methods that make use of lasers are often expensive and large. Indirect measurement principles have been described in literature that seems very suited as ammonia sensing devices. Such systems are suited for miniaturization and integration to make them suitable for measuring in the small gas volumes that are normally available in medical applications like diagnostic breath analysis equipment.

/pdf/ammonia-sensors-and-their-applications-a-review-35hg34lbf3.pdf

Ammonia sensors and their applications - a review

Polydimethylsiloxane (PDMS) is a commercially available physically and chemically stable silicone rubber. It has a unique flexibility with a shear elastic modulus due to one of the lowest glass transition temperatures of any polymer . Further properties of PDMS are a low change in the shear elastic modulus versus temperature , virtually no change in G versus frequency and a high compressibility. Because of its clean room processability, its low curing temperature, its high flexibility, the possibility to change its functional groups and the very low drift of its properties with time and temperature, PDMS is very well suited for micromachined mechanical and chemical sensors, such as accelerometers (as the spring material) and ISFETs (as the ion selective membrane). It can also be used as an adhesive in wafer bonding, as a cover material in tactile sensors and as the mechanical decoupling zone in sensor packagings.

/pdf/the-mechanical-properties-of-the-rubber-elastic-polymer-2jbsjlg7z9.pdf

The mechanical properties of the rubber elastic polymer polydimethylsiloxane for sensor applications

This review paper presents hydrogel-based devices for biomedical applications. The first part of the paper gives a comprehensive, qualitative, theoretical overview of hydrogels' synthesis and operation. Crosslinking methods, operation principles and transduction mechanisms are discussed in this part. The second part includes applications of hydrogel devices in specific fields of interest. Sensing, fluid control, drug delivery, nerve regeneration and other biomedical applications constitute the main focus of this part. The aim of this paper is to briefly present recent advances of the field, without neglecting older ones, and to discuss important or novel concepts of each. (C) 2010 Elsevier B.V. All rights reserved.

Hydrogel-based devices for biomedical applications

Silicon micromachining has successfully been applied to fabricate piezoelectric, piezoresistive and capactive microphones. The use of silicon has allowed the fabrication of microphones with integrated electronic circuitry and the development of the new FET microphone. The introduction of lithographic techniques has resulted in microphones with very small (1 mm2) diaphragms and with specially shaped backplates. The application of corrugated diaphragms seems a promising future development for silicon microphones. It is concluded from a noise consideration that the FET microphone shows a high noise level, which is mainly due to the small sensor capacitance. From this noise consideration, it can be shown that integration of a capacitive microphone and a preamplifier will result in a further reduction of the noise.

/pdf/a-review-of-silicon-microphones-5ebubcl31f.pdf

A review of silicon microphones

A plastic micropump which can be produced using conventional production techniques and materials is presented. By applying well-known techniques and materials, economic fabrication of micropumps for various applications is feasible even at low production volumes. The micropump is capable of pumping both liquid and gas at a considerable high pump rate and is self-priming, which means that it can start pumping gas in a dry state and automatically fills with liquid. Pump rates, at actuation frequencies between 2 and 500 Hz, were around 2 ml/min for water and up to 50 ml/min for air. A differential pressure of 1.25×104 Pa (125 cm water column) was reached. Basically, the micropump consists of two parts, a flat valve assembly with two passive membrane valves and an actuator placed on top. The valves were made by sandwiching a punched thin polymer film between two plastic valve parts containing the valve seats. The latter parts are made by reactive injection molding of an epoxy resin. Two types of actuators have been applied to drive the pump; an electromagnetic actuator consisting of a magnet placed in a coil and secondly a disk. The first actuator, when combined with a flexible polymer pump membrane, showed a very large pump rate for gas, up to 40 ml/min at the resonant frequency of the actuator system. A disadvantage of the electromagnetic actuator was the relatively large volume occupied by the coil giving the micropump final dimensions of 10×10×8 mm3. Application of the piezoelectric actuator reduced these dimensions down to 12×12×2 mm3 with comparable performance.

Wouter Olthuis

Papers

Ammonia sensors and their applications - a review

The mechanical properties of the rubber elastic polymer polydimethylsiloxane for sensor applications

Hydrogel-based devices for biomedical applications

A review of silicon microphones

A plastic micropump constructed with conventional techniques and materials