Enzyme immobilization is an established method for the enhancement of enzyme stability and reusability, two factors that are of great importance for industrial biocatalytic applications. Immobilization can be achieved by different methods and on a variety of carrier materials, both organic and inorganic. Inorganic materials provide the advantage of high stability and long service life which, together with the prolonged service life of the immobilized enzyme, can benefit the process economy. However, enzyme immobilization and increased stability often come at the cost of decreased enzyme activity. The main challenges involved in the design of an efficient immobilized enzyme system is to obtain both retention of high enzyme activity, enhanced stability and reusability, which is a complicated task, given the many variables involved, and the large numbers of methods and materials available. Simultaneously, new carrier materials and morphologies are constantly being developed. An investigation of enzyme immobilization systems on inorganic materials, with special emphasis on inorganic membranes, has been conducted in order to evaluate the effects of the immobilization system on the enzyme properties upon immobilization, i.e., activity, stability and reusability. The material properties of the enzyme carriers (particles and membranes) and their effects on the success of immobilization are described here. Furthermore, the reuse of inorganic membranes as enzyme carriers has been investigated and the reported examples show high ability of regeneration. To the best of our knowledge, this is the first review on enzyme immobilization focusing on the three fundamental aspects to consider when dealing with the topic: catalytic properties, enzyme leakage and reusability. Abbreviations: β‐Gal: β‐d‐galactosidase; ADH: alcohol dehydrogenase; AFM: atomic force microscopy; APTES: 3‐aminopropyltriethoxysilane; APTMS: 3‐aminopropyltrimethoxysilane; BPA: bisphenol A; BSA: bovine serum albumin; CA: carbonic anhydrase; CALB: Candida antartica lipase B; CD: circular dichroism; CDI: carbonyldiimidazole; CLEA: cross‐linked enzyme aggregates; CLSM: confocal laser scanning microscopy; CNT: carbon nanotube; CPG: controlled pore glass; CRL: Candida rugosa lipase; DMeDMOS: dimethyldimethoxysilane; DRIFT: diffuse reflectance Fourier transform infrared; E2: 17β‐estradiol; EDC: N‐(3‐dimethylaminopropyl)‐N′‐ethylcarbodiimide hydrochloride; EDS: electron dispersive spectroscopy; FDH: formate dehydrogenase; FESEM: field emission scanning microscopy; FT‐IR: Fourier transform infrared spectroscopy; GA: glutaraldehyde; GCSZn: coal fly ashes glass‐ceramic zinc sulfate; GOD: glucose oxidase; GPS: 3‐(glycidyloxypropyl)trimethoxysilane; HDMI: hexamethylene diisocyanate; HRP: horseradish peroxidase; IEP: isoelectric point; IPTES: (3‐isocyanatopropyl)triethoxysilane; IR: infrared spectroscopy; LbL: layer‐by‐layer: MCP: metallic ceramic powder; MeTEOS: methyltriethoxysilane; MF: microfiltration; MML: Mucor miehei lipase; MNP: magnetic nanoparticle; MPTMS: 3‐mercaptopropyltrimethoxysilane; NHS: N‐hydroxysuccinimidyl; PAH: poly(allylamine hydrochloride); PEI: polyethyleneimine; PEG: polyethylene glycol; PES: polyether sulfone; PM‐IRRAS: polarization modulation infrared reflection absorption spectroscopy; pNPA: para‐nitrophenyl acetate; pNPP: para‐nitrophenyl palmitate; PSS: polystyrene sulfonate; PTMS: phenyltrimethoxysilane; ROL: Rhizopus oryzae lipase; SCAD: Saccharomyces cerevisiae alcohol dehydrogenase; SDS: sodium dodecyl sulfate; SDS‐2: sodium dodecyl sulfonate; SEM: scanning electron microscopy; TEM: transmission electron microscopy; TEOS: tetraethoxysilane; TGA: thermogravimetric analysis; TLL: Thermomyces lanuginosa lipase; TMP: transmembrane pressure; TTIP: titanium tetraisoproxide; TVL: Trametes versicolor laccase; UF: ultrafiltration; VTMS: vinyltrimethylsilanemagnified image

The hybrid pixel detectors used in the high energy physics experiments currently under construction use a vertical connection technique, the so-called bump bonding. As the pitch below 100 µm, required in these applications, cannot be fullfilled with standard industrial processes (e.g. the IBM C4 process), an in-house bump bond process using reflowed indium bumps was developed at PSI as part of the R&D for the CMS-pixel detector.The bump deposition on the sensor is performed in two subsequent lift-off steps. As the first photolithographic step a thin under bump metalization (UBM) is sputtered onto bump pads. It is wettable by indium and defines the diameter of the bump. The indium is evaporated via a second photolithographic step with larger openings and is reflowed afterwards. The height of the balls is defined by the volume of the indium. On the readout chip only one photolithographic step is carried out to deposit the UBM and a thin indium layer for better adhesion. After mating both parts a second reflow is performed for self alignment and obtaining high mechanical strength.For the placement of the chips a manual and an automatic machine were constructed. The former is very flexible in handling different chip and module geometries but has a limited throughput while the latter features a much higher grade of automatisation and is therefore much more suited for producing hundreds of modules with a well defined geometry.The reliability of this process was proven by the successful construction of the PILATUS detector. The construction of PILATUS 6M (60 modules) and the CMS pixel barrel (roughly 800 modules) will start in 2005.

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The influence of nanoparticle morphology and filler content on the mechanical and electrical properties of carbon nanoparticle modified epoxy is investigated regarding small volumes. Three types of particles, representing spherical, tubular and layered morphologies are used. A clear size effect of increasing true failure strength with decreasing volume is found for neat and carbon black modified epoxy. Carbon nanotube (CNT) modified epoxy exhibits high potential for strength increase, but dispersion and purity are critical. In few layer graphene modified epoxy, particles are larger than statistically distributed defects and initiate cracks, counteracting any size effect. Different toughness increasing mechanisms on the nano- and micro-scale depending on particle morphology are discussed based on scanning electron microscopy images. Electrical percolation thresholds in the small volume fibres are significantly higher compared to bulk volume, with CNT being found to be the most suitable morphology to form electrical conductive paths. Good correlation between electrical resistance change and stress strain behaviour under tensile loads is observed. The results show the possibility to detect internal damage in small volumes by measuring electrical resistance and therefore indicate to the high potential for using CNT modified polymers in fibre reinforced plastics as a multifunctional, self-monitoring material with improved mechanical properties.