Microsystems Center Bremen

Bremen, Germany

Microsystems Center Bremen

Bremen, Germany
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Jedermann R.,University of Bremen | Lang W.,University of Bremen | Lang W.,Microsystems Center Bremen
Acta Horticulturae | Year: 2017

Temperature variations in reefer containers with fruits regularly occur due to deviating airflow and cooling conditions (DACCs). There is little knowledge about whether DACCs affect only a small area or the complete container load. In seven tests in containers from Costa Rica to Europe since 2009, we observed a high level of spatial temperature variation. Banana pallets are not a perfect rectangular shape and they do not completely fit the inward container dimension, resulting in large variations of gap widths. The effect is enhanced by the biological variance of respiration activity. We set up a computational fluid dynamics (CFD) simulation for the airflow and temperature in a container loaded with bananas to provide a better understanding of DACC effects, because detailed experimental evaluation was not feasible in a commercial cold chain. The complex geometrics of a container with 960 boxes had to be reduced to a two-dimensional model. Almost all DACCs had a predominant local effect. For the following DACCs, cooling was slower only in some affected boxes: (a) blocking of a horizontal channel in one pallet and (b) narrow vertical gaps. Double heat generation by higher respiration activity in part of one pallet also had a predominant local effect. The temperature was between 1.7 and 4.7°C higher than for the reference case with normal airflow conditions at 48 h after the start of cooling. Only circulation bypasses by packing mistakes and a reduction of inlet air speed had a significant effect on the average container temperature, of +0.6°C maximum. Quality problems and losses of full container loads, as regularly reported in ocean transport, cannot be explained by a single DACC according to our simulation results. A combination of at least two DACCs is necessary to cause severe quality problems.

Jedermann R.,University of Bremen | Nicometo M.,Iron Mountain | Uysal I.,University of South Florida | Lang W.,University of Bremen | And 2 more authors.
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences | Year: 2014

The need to feed an ever-increasing world population makes it obligatory to reduce the millions of tons of avoidable perishable waste along the food supply chain. A considerable share of these losses is caused by non-optimal cold chain processes and management. This Theme Issue focuses on technologies, models and applications to monitor changes in the product shelf life, defined as the time remaining until the quality of a food product drops below an acceptance limit, and to plan successive chain processes and logistics accordingly to uncover and prevent invisible or latent losses in product quality, especially following the first-expired-firstout strategy for optimized matching between the remaining shelf life and the expected transport duration. This introductory article summarizes the key findings of this Theme Issue, which brings together research study results from around the world to promote intelligent food logistics. The articles include three case studies on the cold chain for berries, bananas and meat and an overview of different post-harvest treatments. Further contributions focus on the required technical solutions, such as the wireless sensor and communication system for remote quality supervision, gas sensors to detect ethylene as an indicator of unwanted ripening and volatile components to indicate mould infections. The final section of this introduction discusses how improvements in food quality can be targeted by strategic changes in the food chain. © 2014 The Author(s) Published by the Royal Society.

Lucklum F.,University of Bremen | Lucklum F.,Microsystems Center Bremen | Vellekoop M.J.,University of Bremen | Vellekoop M.J.,Microsystems Center Bremen
Procedia Engineering | Year: 2015

We present proof-of-concept devices to validate the suitability of high-resolution stereolithography fabrication, polymer material properties, and increased design freedom for realizing 3D phononic crystals. The maskless, single-step technology enables the fabrication of freeform 3D microstructures with high accuracy, which allows rapid prototyping of novel designs and leads to fast optimization cycles. Experimental results for devices with feature sizes down to 100 μm successfully indicate phononic band gap behavior, which is required for applications as sensor and microsystem structures. © 2015 The Authors. Published by Elsevier Ltd.

Jedermann R.,Institute for Microsensors | Jedermann R.,Microsystems Center Bremen | Potsch T.,University of Bremen | Potsch T.,Bremen Research Cluster for Dynamics in Logistics LogDynamics | And 2 more authors.
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences | Year: 2014

Remote measurement of product core temperature is an important prerequisite to improve the cool chain of food products and reduce losses. This paper examines and shows possible solutions to technical challenges that still hinder practical applications of wireless sensor networks in the field of food transport supervision. The high signal attenuation by water-containing products limits the communication range to less than 0.5m for the commonly used 2.4GHz radio chips. By theoretical analysis of the dependency of signal attenuation on the operating frequency, we show that the signal attenuation can be largely reduced by the use of 433MHz or 866MHz devices, but forwarding of messages over multiple hops inside a sensor network is mostly unavoidable to guarantee full coverage of a packed container. Communication protocols have to provide compatibility with widely accepted standards for integration into the global Internet, which has been achieved by programming an implementation of the constrained application protocol for wireless sensor nodes and integrating into IPv6-based networks. The sensor's battery lifetime can be extended by optimizing communication protocols and by in-network preprocessing of the sensor data. The feasibility of remote freight supervision was demonstrated by our full-scale 'Intelligent Container' prototype. © 2014 The Author(s) Published by the Royal Society.

Jedermann R.,University of Bremen | Jedermann R.,Microsystems Center Bremen | Praeger U.,Leibniz Institute for Agricultural Engineering | Geyer M.,Leibniz Institute for Agricultural Engineering | And 3 more authors.
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences | Year: 2014

Quality problems occurring during or after sea transportation of bananas in refrigerated containers are mainly caused by insufficient cooling and nonoptimal atmospheric conditions, but also by the heat generated by respiration activity. Tools to measure and evaluate these effects can largely help to reduce losses along the banana supply chain. The presented green life model provides a tool to predict the effect of deviating temperature, relative humidity, and CO2 and O2 gas concentrations on the storage stability of bananas. A second thermal model allows evaluation of the cooling efficiency, the effect of changes in packaging and stowage and the amount of respiration heat from the measured temperature curves. Spontaneous ripening causes higher respiration heat and CO2 production rate. The resulting risk for creation of hot spots increases in positions in which the respiration heat exceeds the available cooling capacity. In case studies on the transport of bananas from Costa Rica to Europe, we validated the models and showed how they can be applied to generate automated warning messages for containers with reduced banana green life or with temperature problems and also for remote monitoring of the ripening process inside the container. © 2014 The Author(s) Published by the Royal Society.

Dumstorff G.,University of Bremen | Dumstorff G.,Microsystems Center Bremen | Paul S.,Microsystems Center Bremen | Paul S.,University of Bremen | And 2 more authors.
IEEE Sensors Journal | Year: 2014

The basic challenge in embedding sensors in materials is to meet simultaneously two conflicting requirements; on one hand, we want to retrieve sensor data from the material and thus we have to integrate sensors, electronics, and interconnections. On the other hand, sensors are foreign bodies in the material, which may deteriorate its macroscopic properties. This paper discusses several possibilities to integrate sensors in material in a minimal invasive way, avoiding subsequent deterioration of its macroscopic performance. It is our idea to adapt the integrated sensor to the surrounding matrix and to reduce sensors volume to the minimum, which is needed to guarantee the function. This approach is called function scale integration. © 2014 IEEE.

Akhtar M.,University of Bremen | Akhtar M.,Microsystems Center Bremen | Van Den Driesche S.,University of Bremen | Van Den Driesche S.,Microsystems Center Bremen | And 2 more authors.
18th International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2014 | Year: 2014

We present a novel microfluidic on-chip droplet storage system where droplets are generated, stored, and used as culturing chamber for bacteria. Conventionally, droplets are generated in a poly(dimethylsiloxane) (PDMS) chip. O2 and CO2 can easily propagate through this gas permeable polymer, which can be advantageous for cell-based studies. However, this permeability also has a major drawback, namely, that water diffuses through the PDMS chip too yielding droplet evaporation during storage. In this study, droplet evaporation is prevented by coating the inner wall of the PDMS channels with the biocompatible and chemically inert material parylene-AF4 allowing long term droplet storage on-chip. © 14CBMS.

Janssen S.,University of Bremen | Janssen S.,Microsystems Center Bremen | Tessmann T.,University of Bremen | Tessmann T.,Microsystems Center Bremen | And 2 more authors.
Sensors and Actuators, B: Chemical | Year: 2014

Using a large-capacity-on-chip preconcentrator device for selective ethylene measurement leads to some challenges. The dramatic increase of the water influence and the gas chromatography effect of the preconcentrator must be known and compensated before a good measurement with this new device can be performed. Nevertheless, after facing these challenges the small gas chromatograph presented in this paper was for the first time able to detect an ethylene concentration of 170 ppbv. Deduced from this measurement a detection limit below 50 ppbv can be reached, which is absolutely mandatory for shelf life prediction of climacteric fruits. New stationary phases were tested. The used packed gas chromatography column is now capable of separating vaporized water and ethylene gas from each other, which was a breakthrough in the analysis of ethylene concentrations in ambient air. It can be predicted that the system will be available at a price under 1000 €. © 2014 Published by Elsevier B.V.

Ibragimov A.,University of Bremen | Ibragimov A.,Microsystems Center Bremen | Pleteit H.,Fraunhofer Institute for Manufacturing Engineering and Applied Materials Research | Pille C.,Fraunhofer Institute for Manufacturing Engineering and Applied Materials Research | And 2 more authors.
IEEE Electron Device Letters | Year: 2012

A thermoelectric generator (TG) directly embedded in aluminum is described. The device has been realized using a new silicon thermocouple process with very high temperature stability. It is integrated by direct embedding in the liquid aluminum during casting. The TG generates up to 500 μW of external electric power. The new technology also opens the path to a new generation of sensors and microsystems embedded in metals during primary shaping. © 2011 IEEE.

Jedermann R.,University of Bremen | Poetsch T.,Bremen Research Cluster for Dynamics in Logistics | Lang W.,Microsystems Center Bremen
Smart SysTech 2014; European Conference on Smart Objects, Systems and Technologies | Year: 2015

Food losses along the cold chain can be reduced by accurate monitoring of the transport conditions. After 10 years of research on the 'Intelligent Container' we summarize our results in regard to the following questions: a) What are the challenges in establishing a wireless communication systems that links sensors inside food packing with global networks? b) Which sensors are most useful to detect deviations of food quality? c) Which improvements in the food chain are possible if detailed data about temperature and quality deviations are provided? d) What level of intelligence or smartness can be implemented on sensor or container level? © 2014 VDE Verlag.

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