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Integration of motor enzymes with biological nanopores has enabled commercial DNA sequencing technology; yet studies of the similar principle applying to solid-state nanopores are limited. Here, we demonstrate the real-life monitoring of phi29 DNA polymerase (DNAP) docking onto truncated-pyramidal nanopore (TPP) arrays through both electrical and optical readout. To achieve effective docking, atomic layer deposition of hafnium oxide is employed to reduce the narrowest pore opening size of original silicon (Si) TPPs to sub-10 nm. On a single TPP with pore opening size comparable to DNAP, ionic current measurements show that a polymerase-DNA complex can temporally dock onto the TPP with a certain docking orientation, while the majority become translocation events. On 5-by-5 TPP arrays, a label-free optical detection method using Ca2+ sensitive dye, are employed to detect the docking dynamics of DNAP. The results show that this label-free detection strategy is capable of accessing the docking events of DNAP on TPP arrays. Finally, we examine the activity of docked DNAP by performing on-site rolling circle amplification to synthesize single-stranded DNA (ssDNA), which serves as a proof-of-concept demonstration of utilizing this docking scheme for emerging nanopore sensing applications.

Herein the coupling of a miniaturized, nanoliter scaled, pressure regulator (chipPR), and a chipHPLC device is introduced. The active temperature based flow control of the chipPR is able to generate rapid pressure changes and therefore enables on-chip pinched injection and flow gradients with reduced instrumental effort and minimal dead volumes. The functionality of the chipPR empowered chipHLPC device was demonstrated with high-speed HPLC-separations applying fluorescence and electrospray mass spectrometry (ESI-MS) detection. The system shows excellent long-term stability of chromatography integrity (retention times with RSD of 0.44-0.91%) due to the integration of a PID feedback regulation. This first chip-based HPLC device equipped with chipPRs enables precise flow control with significantly reduced technical effort compared to the state-of-the-art.

In microfluidics, a well-known challenge is to obtain reproducible results, often constrained by unstable pressures or flow rates. Today, there are existing stabilisers made for low-pressure microfluidics or high-pressure macrofluidics, often consisting of passive membranes, which cannot stabilise long-term fluctuations. In this work, a novel stabilisation method that is able to handle high pressures in microfluidics is presented. It is based on upstream flow capacitance and thermal control of the fluid's viscosity through a PID controlled restrictor-chip. The stabiliser consists of a high-pressure-resistant microfluidic glass chip with integrated thin films, used for resistive heating. Thereby, the stabiliser has no moving parts. The quality of the stabilisation was evaluated with an ISCO pump, an HPLC pump, and a Harvard pump. The stability was greatly improved for all three pumps, with the ISCO reaching the highest relative precision of 0.035% and the best accuracy of 8.0 ppm. Poor accuracy of a pump was compensated for in the control algorithm, as it otherwise reduced the capacity to stabilise longer times. As the dead volume of the stabiliser was only 16 nL, it can be integrated into micro-total-analysis- or other lab-on-a-chip-systems. By this work, a new approach to improve the control of microfluidic systems has been achieved. De två första författarna delar förstaförfattarskapet.

Microfluidics exploiting the phenomenon of inertial focusing have attracted much attention in the last decade as they provide the means to facilitate the detection and analysis of rare particles of interest in complex fluids such as blood and natural water. Although many interesting applications have been demonstrated, the systems remain difficult to engineer. A recently presented line of the technology, inertial focusing in High Aspect Ratio Curved microfluidics, has the potential to change this and make the benefits of inertial focusing more accessible to the community. In this paper, with experimental evidence and fluid simulations, we provide the two necessary equations to design the systems and successfully focus the targets in a single, stable, and high-quality position. The experiments also revealed an interesting scaling law of the lift force, which we believe provides a valuable insight into the phenomenon of inertial focusing.

A novel wearable smart patch can monitor various aspects of physical activity, including the dynamics of running, but like any new device developed for such applications, it must first be tested for validity. Here, we compare the step rate while running in place as measured by this smart patch to the corresponding values obtained utilizing ‘‘gold standard’’ MEMS accelerometers in combination with bilateral force plates equipped with HBM load cells, as well as the values provided by a three-dimensional motion capture system and the Garmin Dynamics Running Pod. The 15 healthy, physically active volunteers (age = 23 ± 3 years; body mass = 74 ± 17 kg, height = 176 ± 10 cm) completed three consecutive 20-s bouts of running in place, starting at low, followed by medium, and finally at high intensity, all self-chosen. Our major findings are that the rates of running in place provided by all four systems were valid, with the notable exception of the fast step rate as measured by the Garmin Running Pod. The lowest mean bias and LoA for these measurements at all rates were associated consistently with the smart patch.

For the facile use of liquid metal composites (LMCs) for soft, stretchable and thermal systems, it is crucial to understand and predict the thermal conductivity of the composites as a function of liquid metal (LM) volume fraction and applied strain. In this study, we investigated the effective thermal conductivity of LMCs based on various mean-field homogenization frameworks including Eshelby, Mori-Tanaka, differential and double inclusion methods. The double inclusion model turned out to make the prediction closest to the experimental results in a wide range of LM volume fractions. Interestingly, we found that the theoretical models based on the assumption of ideal LM dispersion and zero interfacial resistance underestimated the thermal conductivity compared to the experimental results in a low volume fraction regime. By considering the accompanied variations in the LM inclusion's aspect ratios under a typical size distribution of inclusions (∼μm), the change of effective thermal conductivity was predicted under a uniaxial 300% tensile strain. Our study will deepen the understanding of the thermal properties of LMCs and support the designs of stretchable thermal interfaces and packaging with LMCs in the future.

Fiber – a primitive yet ubiquitous form of material – intertwines with our bodies and surroundings, from constructing our fibrous muscles that enable our movement, to forming fabrics that intimately interface with our skin. In soft robotics and advanced materials science research, actuated fibers are gaining interest as thin, flexible materials that can morph in response to external stimuli. In this paper, we build on fluidic artificial muscles research to develop OmniFiber - a soft, line-based material system for designing movement-based interactions. We devised actuated thin (oouter

The ability to focus, separate and concentrate specific targets in a fluid is essential for the analysis of complex samples such as biological fluids, where a myriad of different particles may be present. Inertial focusing is a very promising technology for such tasks, and specially a recently presented variant, inertial focusing in High Aspect Ratio Curved systems (HARC sytsems), where the systems are easily engineered and focus the targets together in a stable position over a wide range of particle sizes and flow rates. However, although convenient for laser interrogation and concentration, by focusing all particles together, HARC systems lose an essential feature of inertial focusing: the possibility of particle separation by size. Within this work, we report that HARC systems not only do have the capacity to separate particles but can do so with extremely high resolution, which we demonstrate for particles with a size difference down to 80 nm. In addition to the concept for particle separation, a model considering the main flow, the secondary flow and a simplified expression for the lift force in HARC microchannels was developed and proven accurate for the prediction of the performance of the systems. The concept was also demonstrated experimentally with three different sub-micron particles (0.79, 0.92 and 1.0 µm in diameter) in silicon-glass microchannels, where the resolution in the separation could be modulated by the radius of the channel. With the capacity to focus sub-micron particles and to separate them with high resolution, we believe that inertial focusing in HARC systems is a technology with the potential to facilitate the analysis of complex fluid samples containing bioparticles like bacteria, viruses or eukaryotic organelles.

Purpose The purpose of this paper is to explore, describe and categorise practices of managing product returns empirically in internet retailing. Design/methodology/approach A multiple case study was conducted involving 12 e-commerce firms and 4 logistics service providers. An integrative data collection approach of semi-structured interviews, documentation and observations was used to gain comprehensive managerial and operational descriptions of returns management (RM) processes. Findings The findings show inconsistent RM processes, with a plethora of practices implemented and organised differently across firms. RM processes are ambiguous; their design is a result of incremental changes over time, lacking strategy and goals. There is a mismatch between how they are described and understood in the literature and how they are actually used. Practices in gatekeeping, avoidance and reverse logistics are defined and categorised. These serve as a typology of practices for managers to (re)consider, along with 15 propositions on how RM is practised. Research limitations/implications The range of RM practices and the processes reflect a lack of scholarly attention and strategic view. Research is needed to develop clear goals on how the RM process can be better aligned with business strategies. Practical implications The typology of practices is a benchmark for internet retailers in their design of efficient RM processes. Originality/value Systematic and empirical research on RM is scarce compared to forward management. The study bridges this gap as one of the first to describe RM practices in depth, define service as a key activity, and identify a mismatch between theory and practice.

The remarkable growth of e-commerce has defined the recent years of various industries worldwide. Driven by consumers, the e-commerce surge (e-retail in particular) stems from the final leg of the supply chain: the last mile. As the growing flow of e-commerce orders continues to generate new records for annual revenues, key actors in the last mile face the challenges of increasing customer demands and transportation volumes. In response, e-retailers and logistics service providers seek innovative service solutions, often powered by technological advancements. This study consisted of focus group interviews and a usability test that incorporated an innovative technology in the delivery service. The study provides insights into how service innovation affects e-customer behavior and presents a basic map of the e-customer journey. The findings also provide a foundation for improving management of the customer experience and aiding managerial decision-making when designing new e-commerce last mile services.

Nowadays, stretchable/epidermal electronics based on liquid alloys has attracted more and more attention, and various processing techniques have subsequently been developed to demonstrate diverse applications never seen before. However, to fully exploit its potential advantages, epidermal electronics is still searching for a technique meeting all demands on resolution, pattern complexity, and operational flexibility. In this study, we propose a technique that allows for complex and high-density patterns on thin stretchable substrates by combining ultraviolet laser patterning of a modified water-soluble mask, atomized spray deposition of liquid alloys on a flexible temporary substrate, lift-off by water dissolving, and finally, component integration and encapsulation. With this new technique, it was possible to make epidermal precision strain sensors with liquid alloy patterns of high density, which were capable of monitoring fine local skin movements such as the detailed process of wrinkle formation as well as the overall motion of the body part. In addition, this process is highly efficient and well controllable, with high potential for possible industrial automation and massive production.

For various industries worldwide, recent years have been defined by the remarkable growth of e-commerce. Enabled by the Internet, retailers can reach more customers, spread much further in the dist...

Binary CO2-alcohol mixtures, such as CO2-expanded liquids (CXLs), are promising green solvents for reaching higher performance in flow chemistry and separation processing. However, their compressib ...

Fine manipulation of particles is essential for the analysis of complex samples such as blood or environmental water, where rare particles of interest may be masked by millions of others. Inertial focusing is amongst the most promising techniques for this task, enabling label-free manipulation of particles with sub-micron resolution at very high flow rates. However, the phenomenon still remains difficult to predict due to the focus position shifting in tortuous ways as function of the channel geometry, flow rate and particle size. Here, we present a new line of microfluidics that exploit inertial focusing in High Aspect Ratio Curved (HARC) microchannels and overcome this limitation. Consisting of a single curved channel, HARC systems provide a highly predictable, single focus position near the centre of the inner wall, largely independent of the flow rate and particle size. An explanation of the mechanism of migration and focus of particles, together with its governing equations, is provided based on simulations in COMSOL Multiphysics and experimental results. HARC microchannels built in silicon-glass were used for experimental validation, achieving a high quality, single focus position for a range of microparticles with sizes of 0.7 - 1 µm and bacterial cells (Escherichia coli). The recovery of 1 µm particles was 99.84% with a factor four in concentration. With a stable focus position, we envision that HARC systems will bring the technology closer to implementation in laboratories for analysis of complex fluids with biological particles like cells and organelles.

Microfluidics exploiting the phenomenon of inertial focusing have attracted much attention in the last decade, as they provide the means to facilitate the detection and analysis of rare particles of interest in complex fluids such as blood and natural water. Although many interesting applications have been demonstrated, the systems remain difficult to engineer. A recently presented line of the technology, inertial focusing in High Aspect Ration Curved (HARC) microfluidics, has the potential to change this and make the benefits of inertial focusing more accessible to the community. In this paper, with experimental evidence and fluid simulations, we provide the two necessary equations to design the systems and successfully focus the desired targets in a single, stable, and high-quality position. Last, the experiments revealed an interesting scaling law of the lift force, which we believe provides a valuable insight into the phenomenon of inertial microfluidics.

Solid-state nanopore arrays hold promises for high-throughput optical analysis of single molecules. However, the high photoluminescence (PL) background emanating from the commonly used silicon nitride (SiNx) membrane for nanopore fabrication and the nonspecific adsorption of analyte on the pore sidewalls have plagued the high sensing sensitivity and efficiency offered by optical sensing. Here, the present work demonstrates an optical monitoring system using a truncated pyramidal nanopore array on a silicon membrane coated with a lipid bilayer for visualization of DNA translocation events. The silicon membrane produces essentially no PL under blue-green laser illumination, which enables more clear identification of DNA translocation and clogging events than using SiNx-based devices. The lipid bilayer coating based on small unilamellar vesicles (SUVs) minimizes the nonspecific adsorption of DNA. With confocal microscopy, the fluorescent labeled DNA translocation motion is visualized in three dimensions. The statistical results show that the percentage of DNA clogged pores is significantly reduced for the lipid bilayer coated nanopores as compared to the uncoated nanopores.

Interfacing solid-state nanopores with biological systems has been exploited as a versatile analytical platform for analysis of individual biomolecules. Although clogging of solid-state nanopores due to nonspecific interactions between analytes and pore walls poses a persistent challenge in attaining the anticipated sensing efficacy, insufficient studies focus on elucidating the clogging dynamics. Herein, we investigate the DNA clogging behavior by passing double-stranded (ds) DNA molecules of different lengths through hafnium oxide(HfO2)-coated silicon (Si) nanopore arrays, at different bias voltages and electrolyte pH values. Employing stable and photoluminescent-free HfO2/Si nanopore arrays permits a parallelized visualization of DNA clogging with confocal fluorescence microscopy. We find that the probability of pore clogging increases with both DNA length and bias voltage. Two types of clogging are discerned: persistent and temporary. In the time-resolved analysis, temporary clogging events exhibit a shorter lifetime at higher bias voltage. Furthermore, we show that the surface charge density has a prominent effect on the clogging probability because of electrostatic attraction between the dsDNA and the HfO2 pore walls. An analytical model based on examining the energy landscape along the DNA translocation trajectory is developed to qualitatively evaluate the DNA-pore interaction. Both experimental and theoretical results indicate that the occurrence of clogging is strongly dependent on the configuration of translocating DNA molecules and the electrostatic interaction between DNA and charged pore surface. These findings provide a detailed account of the DNA clogging phenomenon and are of practical interest for DNA sensing based on solid-state nanopores.

Among numerous patterning techniques, masked liquid alloy printing is one of the most promising techniques for scalable fabrication of liquid-alloy-based stretchable electronics. Like any other mask-based process, its resolution is often constrained by the quality of the mask, and the fabrication cost increases drastically with increased resolution. In this work, by introducing a sandwiched thermal shrink polymer film masking technique and a corresponding intermediate release agent, fine liquid alloy patterns were demonstrated by using a mechanical cutting plotter together with a common oven. The final resolution and shape of the mask could be tuned based on the anisotropy of the shrink polymer film and other operational parameters of the technique. After shrinkage, the width of the patterned liquid alloy lines and space in-between could be tuned to less than one third of the original cut pattern, to about 35 and 60 μm, respectively, according to requirements. To better predict the final structure, severa...

Flow control is central to microfluidics and chromatography. With decreasing dimensions and high pressures, precise fluid flows are often needed. In this paper, a high-pressure flow control system is presented, allowing for the miniaturization of chromatographic systems and the increased performance of microfluidic setups by controlling flow, composition, and relative permittivity of two-component flows with CO2. The system consists of four chips: two flow actuator chips, one mixing chip, and one relative permittivity sensor. The actuator chips, throttling the flow, required no moving parts as they instead relied on internal heaters to change the fluid resistance. This allows for flow control using miniaturized fluid delivery systems containing only a single pump or pressure source. Mobile phase gradients between 49% and 74% methanol in CO2 were demonstrated. Depending on how the actuator chips were dimensioned, the position of this range could be set for different method-specific needs. With the microflu...

This study explores customer value in relation to parcel lockers, a self-service tool that reshapes the delivery and returns experience in the context of e-commerce last mile delivery. Parcel lockers offer a response to retail and last mile delivery challenges provoked by the rapid growth of e-commerce worldwide. Retailers, logistics service providers, communities, and other stakeholders now face issues due to increased volumes of goods sold online. The introduction of parcel lockers to service algorithms is intended to address these issues by involving consumers in the service process. However, the existing research fails to provide knowledge about the customer's view on this new technological solution. This study followed a focus group design and built on grounded theory to provide insights into customer value in relation to parcel lockers. These insights can contribute to both research and practice.

The rapid development of biosensing platforms for highly sensitive and specific detection raises the desire of precise localization of biomolecules onto various material surfaces. Aluminum has been strategically employed in the biosensor system due to its compatibility with CMOS technology and its optical and electrical properties such as prominent propagation of surface plasmons. Herein, we present an adaptable method for preparation of carbon nanoarrays on aluminum surface passivated with poly(vinylphosphonic acid) (PVPA). The carbon nanoarrays were defined by means of electron beam induced deposition (EBID) and they were employed to realize site-specific immobilization of target biomolecules. To demonstrate the concept, selective streptavidin/neutravidin immobilization on the carbon nanoarrays was achieved through protein physisorption with a significantly high contrast of the carbon domains over the surrounding PVPA-modified aluminum surface. By adjusting the fabrication parameters, local protein dens...

A system consisting of a high-pressure tolerant microfluidic glass chip, high-speed absorbance imaging, and image processing has been developed to study rapid dynamic events like pH change in a multiphase flow. The system gives both kinetic and quantitative equilibrated information. By tracking the interactions of aqueous additive mixtures and liquid CO2, at 80 bar and 24 °C, under flow, measurement at a given P, T condition is done in 0.25 s. The acidification rate to steady state was found to be mass transport limited, occurring in less than 1 s. For 30 mM of the additives ammonium acetate and ammonium formate, equilibrium pH of 4.5 and 4.1, respectively, was seen. These additives are of key importance in common mobile phases used in SFC. (Less)

Recasting prior work on return-policy and purchase intentions literature, through the lens of signaling theory and relational signaling theory, we posit that returns policy, as a market signaling mechanism, is a costly investment that online retailers make to not only support current transaction but also to signal commitment towards customer service. What outcome would such costly signal result into? Based on relational signaling theory, it promotes trust, that in turn, could enhance purchase intentions. With empirical data from 730 online consumers of fast-moving consumer goods in Sweden, the study finds that, after controlling for shoppers’ age, education, income, gender, and frequency of online purchases, perceived consumer trust fully mediates the effect of perceived return policy leniency on purchase intention. Building on past research, we apply a different theoretical lens that connects costly signaling that drives relational signaling to foster customer trust to improve purchase intentions.

In this study, we used a low-temperature hydrothermal technique to fabricate arrays of sensors with ZnO nanorods grown on-chip. The sensors on the glass substrate then were sputter decorated with P ...

A soft and highly directive, proximity-coupled split-ring resonator fabricated with a liquid alloy, copper and polydimethylsiloxane (PDMS) is presented. The same was designed for sensing osteogenesis of calvarial bone. As dielectric properties of bone grafts in ossifying calvarial defects should change during the osteogenesis process, devices like this could monitor the gradual transformation of the defect into bone by differentiating changes in the dielectric properties as shifts in the resonance frequency. Computational Software Technology (CST) Microwave Studio®-based simulation results on computational head models were in good agreement with laboratory results on head phantom models, which also included the comparison with an in-vivo measurement on the human head. A discussion based on an inductive reasoning regarding dynamics’ considerations is provided as well. Since the skin elasticity of newborn children is high, stretching and crumpling could be significant. In addition, due to typical head curvatures in newborn children, bending should not be a significant issue, and can provide higher energy focus in the defect area and improve conformability. The present concept could support the development of soft, cheap and portable follow-up monitoring systems to use in outpatient hospital and home care settings for post-operative monitoring of bone healing after reconstructive surgical procedures.

This work presents a versatile and facile method for precise localization of nanoparticles on solid-state nanopores surface-functionalized with carbon via electron beam induced deposition (EBID). For the first time, EBID of carbon is demonstrated to enable nanoparticle localization on solid-state nanopores. To avoid non-specific adsorption of nanoparticles on the surface, an atomic layer deposited Al 2 O 3 layer in combination with phosphonate passivation is used. By tuning the electron dose in the EBID process, the loading fraction of nanoparticles on carbon nanoarrays can be varied on similarly sized domains. Nanoparticle loading driven by electrophoresis can achieve an efficiency that is orders of magnitude higher than that driven by diffusion.

In this paper, we study inertial focusing in curved channels and demonstrate the alignment of particles with diameters between 0.5 and 2.0 μm, a range of biological relevance since it comprises a multitude of bacteria and organelles of eukaryotic cells. The devices offer very sensitive control over the equilibrium positions and allow two modes of operation. In the first, particles having a large variation in size are focused and concentrated together. In the second, the distribution spreads in a range of sizes achieving separation with sub-micron resolution. These systems were validated with three bacteria species (Escherichia coli, Salmonella typhimurium and Klebsiella pneumoniae) showing good alignment while maintaining the viability in all cases. The experiments also revealed that the particles follow a helicoidal trajectory to reach the equilibrium positions, similar to the fluid streamlines simulated in COMSOL, implying that these positions occupy different heights in the cross section. When the equilibrium positions move to the inner wall as the flow rate increases, they are at a similar distance from the centre than in straight channels (∼0.6R), but when the equilibrium positions move to the outer wall as the flow rate increases, they are closer to the centre and the particles pass close to the inner wall to elevate their position before reaching them. These observations were used along with COMSOL simulations to explain the mechanism behind the local force balance and the migration of particles, which we believe contributes to further understanding of the phenomenon. Hopefully, this will make designing more intuitive and reduce the high pressure demands, enabling manipulation of particles much smaller than a micrometer.

Research on returns policies is scarce and inconclusive. This study is a first attempt to empirically analyze and describe the effects of returns policies on consumer behavior and the moderating effects of the policies on profitability. The method involves analyzing the transactional data of a Swedish online fashion retailer. The results of the regression analyses show that with a lenient returns policy, repeat customers generate a significantly higher contribution per order, while returners and customers who enjoy free returns generate a significantly lower contribution per order. In addition, returners and repeat customers generate a significantly higher total contribution, while customers who enjoy free returns generate a significantly lower total contribution. Hence, returns policies that are free of charge do not necessarily benefit retailers in terms of long-term profitability. From a managerial perspective, the results provide guidance on how to address the recent changes in European consumer legislation.

ZnO nanorods were selectively grown on-chip with a two-step low-temperature hydrothermal method and their gas sensing properties were investigated. Small zinc islands were deposited by sputtering o ...

Synthesis of ultrathin ZnO nanowires gains great attention from research community because oftheir large potential in applications involving optoelectronics and sensors. In this study, a lowpressur ...

Three different ZnO nanostructures, dense nanorods, dense nanowires, and sparse nanowires, were synthesized between Pt electrodes by on-chip hydrothermal growth at 90°C and below. The three nanostructures were characterized by scanning electron microscopy and x-ray diffraction to identify their morphologies and crystal structures. The three ZnO nanostructures were confirmed to have the same crystal type, but their dimensions and densities differed. The NO2 gas-sensing performance of the three ZnO nanostructures was investigated at different operation temperatures. ZnO nanorods had the lowest response to NO2 along with the longest response/recovery time, whereas sparse ZnO nanowires had the highest response to NO2 and the shortest response/recovery time. Sparse ZnO nanowires also performed best at 300°C and still work well and fast at 200°C. The current–voltage curves of the three ZnO nanostructures were obtained at various temperatures, and the results clearly showed that sparse ZnO nanowires did not have the linear characteristics of the others. Analysis of this phenomenon in connection with the highly sensitive behavior of sparse ZnO nanowires is also presented.

Fast photoswitching of wetting properties is important for the development of micro/nanofluidic systems and lab-on-a-chip devices. Here, we show how structuring the surface amplifies photoswitching properties. Atomic layer-deposited titanium dioxide (TiO2) has phototunable hydrophilic properties due to its surface chemistry, but microscale overhang pillars and additional nanoscale topography can override the chemistry and make the surface superhydrophobic. Three switching processes are achieved simply by controlling the UV exposure time: from (1) rolling superhydrophobic to sticky superhydrophobic (Cassie-Baxter to Wenzel), (2) superhydrophobic to hydrophilic, and (3) superhydrophobic to superhydrophilic after 1, 5, and 10 min of UV exposure, respectively. We report the fastest reversible switching to date: 1 min of UV exposure is enough to promote a rolling-to-sticky transition, and mild heating (30 min at 60 °C) is sufficient for recovery. This performance is caused by a combination of the photoswitching properties of TiO2, the micropillar overhang geometry, and surface nanostructuring. We demonstrate that the switching also can be performed locally by introducing microwriting under a water droplet.

Recently, the shrinking of the personal computer market has given a clear signal that it is time to divert our focus from the strategy of miniaturization of transistors to a different strategy with emerging technologies. As a new form of electronics, stretchable electronics has significantly advanced in the past few years by micro/nanofabrication of thin films of traditional stiff and hard materials such as silicon, metals, and ceramics, and especially subsequent transfer process on an elastic substrate. However, such a thin structure often suffers from high resistance that leads to low performance when long structures are required. This is particularly true for antennas in radio-frequency (RF) electronics. By introducing microfluidics into RF electronics, we found out that it was an excellent way to make high-performance stretchable RF electronics. Apart from antennas, the microfluidic approach was also adopted and further developed to various devices with integrated wireless communication. This fusion of microfluidics with RF electronics brings not only a lot of opportunities for researchers as a radically new research field, but also potentially commercial benefits for industry. As a new emerging field, a huge effort, ranging from fundamental science to technology development, is required to realize it. This paper illustrates the fundamentals in processing and relevant applications, and highlights recent advances in microfluidic RF electronics. The authors would like to inspire the electronics community to further exploit the advantages of this approach and accelerate innovations in this field.

Conventional thermoelectric generators (TEGs) are normally hard, rigid, and flat. However, most objects have curvy surfaces, which require soft and even stretchable TEGs for maximizing efficiency of thermal energy harvesting. Here, soft and stretchable TEGs using conventional rigid Bi2Te3 pellets metallized with a liquid alloy is reported. The fabrication is implemented by means of a tailored layer-by-layer fabrication process. The STEGs exhibit an output power density of 40.6 μW/cm2 at room temperature. The STEGs are operational after being mechanically stretched-and-released more than 1000 times, thanks to the compliant contact between the liquid alloy interconnects and the rigid pellets. The demonstrated interconnect scheme will provide a new route to the development of soft and stretchable energy-harvesting avenues for a variety of emerging electronic applications.

High-pressure microfluidics offers fast analyses of thermodynamic parameters for compressed process solvents. However, microfluidic platforms handling highly compressible supercritical CO2 are difficult to control, and on-chip sensing would offer added control of the devices. Therefore, there is a need to integrate sensors into highly pressure tolerant glass chips. In this paper, thin film Pt sensors were embedded in shallow etched trenches in a glass wafer that was bonded with another glass wafer having microfluidic channels. The devices having sensors integrated into the flow channels sustained pressures up to 220 bar, typical for the operation of supercritical CO2. No leakage from the devices could be found. Integrated temperature sensors were capable of measuring local decompression cooling effects and integrated calorimetric sensors measured flow velocities over the range 0.5-13.8 mm/s. By this, a better control of high-pressure microfluidic platforms has been achieved. Part financed through Swedish Agency for the Innovation System, Vinnova, through the Centre for Natural Disaster Science (CNDS)

A qualitative study is presented on how proteins from a complex biological sample are distributed in a microdialysis sample system. A comparison between proteins identified in the human ventricular cerebrospinal fluid (CSF) sample, the collected dialysate and the proteins adsorbed onto the membrane was conducted. The microdialysis experiment was performed in vitro at 37°C for the duration of 24h. Thereafter, the membranes were removed from the catheter and the adsorbed proteins were tryptically digested using the on-surface enzymatic digestion (oSED) protocol. The CSF samples and the dialysates were digested using a standard in-solution trypsin digestion protocol. In the final phase, the samples were analysed using nano-liquid chromatography in combination with tandem mass spectrometry. In the four sample compartments analysed (CSF start, Membrane, Dialysate, CSF end) a total of 134 different proteins were found. However, most of the identified proteins (n=87) were uniquely found in one sample compartment only. Common CSF proteins such as albumin, apolipoproteins and cystatin C together with plasma proteins such as hemoglobin and fibrinogen were among the 11 proteins that were found in all samples. These proteins are present in high concentrations in CSF, which means that they effectively block out the detection signal of less abundant proteins. Therefore, only 25% of the proteins adsorbed onto the membrane were detected in the CSF compared with the dialysate that shared 44% of its proteins with the CSF. The proteins adsorbed onto the membrane were significantly more hydrophobic, had a lower instability index and more thermostable compared to the proteins in the CSF and the dialysate. The results suggest that proteins adsorbed onto the microdialysis membranes may escape detection because they are prevented from passing the membrane into the dialysate. Thus, the membrane needs to be examined after sample collection in order to better verify the protein content in the original sample. This is particularly important when searching for new protein biomarkers for neurodegenerative diseases.

A simple and low-cost approach was proposed for prototyping PDMS based microfluidic devices by transferringadhesive film microstructures onto a flexible substrate as a mould for PDMS replicas. The microstructures were engravedon an adhesive coated film using a commercial cutting plotter and then transferred (or laminated) onto a flexiblesubstrate, allowing for engraved isolated patterns. The proposed technique was demonstrated by a hydrodynamic focusingmicrofluidic device, having splitting and re-combining sheath channels. The whole processing could be finished within 1h in a normal laboratory environment. This approach offers an easy, flexible and rapid prototyping of microfluidic andlab-on-a-chip devices to users without expertise in microfabrication. In addition, by minimizing the use of chemicals, theprocess becomes more environmentally friendly than conventional photolithography based micro-fabrication techniques.

The use of supercritical carbon dioxide (scCO2) as an apolar solvent has been known for decades. It offers a greener approach than, e.g., hexane or chloroform, when such solvents are needed. The use of scCO2 in microsystems, however, has only recently started to attract attention. In microfluidics, the flow characteristics need to be known to be able to successfully design such components and systems. As supercritical fluids exhibit the exciting combination of low viscosity, high density, and high diffusion rates, the fluidic behavior is not directly transferrable from aqueous systems. In this paper, three flow regimes in the scCO2–liquid water two-phase microfluidic system have been mapped. The effect of both total flow rate and relative flow rate on the flow regime is evaluated. Furthermore, the droplet dynamics at the bifurcating exit channel are analyzed at different flow rates. Due to the low viscosity of scCO2, segmented flows were observed even at fairly high flow rates. Furthermore, the carbon dioxide droplet behavior exhibited a clear dependence on both flow rate and droplet length.

This work presents an acoustic trap with integrated thin film sensors to monitor temperature variations during operation. The acoustic trap is wet-etched in glass with a thermally bonded glass lid ...

With the interest of studying larger biomolecules by microdialysis (MD), this sampling technique has reached into the ultrafiltration region of fluid exchange, where fluid recovery (FR) has a strong dependence on pressure. Hence in this study, we focus on the fluid exchange across the high molecular weight cut off MD membrane under the influence of the static pressure in the sampling environment. A theoretical model is presented for MD with such membranes, where FR has a linear dependence upon the static pressure of the sample. Transmembrane (TM) osmotic pressure difference and MD perfusion rate decide how fast FR increases with increased static pressure. A test chamber for in vitro MD under static pressure was constructed and validated. It can hold four MD probes under controlled pressurized conditions. Comparison showed good agreement between experiment and theory. Moreover, test results showed that the fluid recovery of the test chamber MD can be set accurately via the chamber pressure, which is controlled by sample injection into the chamber at precise rate. This in vitro system is designed for modelling in vivo MD in cerebrospinal fluid and studies with biological samples in this system may be good models for in vivo MD.

During the last fifteen years, miniaturised paraffin actuation has evolved through the need of a simple actuation principle, still able to deliver large strokes and high actuation forces at small scales. This is achieved by the large and rather incompressible volume expansion associated with the solid-to-liquid phase transition of paraffin. The common approach has been to encapsulate the paraffin by a stiff surrounding that directs the volume expansion towards a flexible membrane, which deflects in a directed stroke. However, a number of alternative methods have also been used in the literature. The most common applications to this date have been switches, positioning actuators, and microfluidic valves and pumps. This review will treat the historical background, as well as the fundamentals in paraffin actuation, including material properties of paraffin. Besides reviewing the three major groups of paraffin actuator applications; actuators, valves, and pumps, the modelling done on paraffin actuation will be explored. Furthermore, a section focusing on fabrication of paraffin microactuators is also included. The review ends with conclusions and outlook of the field, identifying unexplored potential of paraffin actuation.

Purpose – The purpose of this paper is twofold: first, to empirically test whether a “one size fits all” strategy fits the fashion e-commerce business and second, to evaluate whether consumer returns are a central aspect of the creation of profitability and, if so, to discuss the role of returns management (RM) in the supply chain strategy. Design/methodology/approach – Transactional sales and return data were analysed and used to categorise customers based on their buying and returning behaviours, measuring each customer's net contribution margins. Findings – The e-commerce business collects a vast quantity of data, but these data are seldom used for the development of service differentiation. This study analysed behaviour patterns and determined that the segmentation of customers on the basis of both sales and return patterns can facilitate a differentiated service delivery approach. Research limitations/implications – This research empirically supports the theory that customer buying and returning behaviours can be used to appropriately categorise customers and thereby guide the development of a more differentiated service approach. Practical implications – The findings support a differentiated service delivery system that utilises a more dynamic approach, conserving resources and linking the supply chain and/or organisational strategies with customers' buying and returning behaviours to avoid over and underservicing customers. Originality/value – Consumer returns are often viewed as a negative aspect of doing business; interestingly, however, the authors revealed that the most profitable customer is a repeat customer who frequently returns goods.

This study aims to explore the influence of free delivery and free returns on the purchasing and return behaviour of real e-customers in the marketplace. To accomplish this goal, we conducted the study as a fully randomised and controlled experiment in cooperation with nelly.com, a Nordic e-commerce site that specialises in fashion and beauty. Our results suggest that a lenient delivery policy is associated with increased order frequency, decreased average value of purchased items, increased probability of return, and increased average value of returned items. In addition, a lenient return policy was found to be associated with increased order frequency, a decrease in the average value of orders, a decrease in the average value of purchased items, and increased probability of return. However, the effect sizes are generally small, and we conclude that factors such as legislation and competition often force e-tailers to offer free delivery and free returns even though such offers probably would not have been profitable otherwise.

Presented in this paper is a finite-element-method-based model for phase change material actuators, modeling the active material as a fluid as opposed to a solid. This enables the model to better conform to localized loads and offering the opportunity to follow material movement in enclosed volumes. Modeling, simulation, and analysis of an electrothermally activated paraffin microactuator have been conducted. The paraffin microactuator used for the analysis in this study exploits the large volumetric expansion of paraffin upon melting, which, combined with its low compressibility in the liquid state, allows for high hydraulic pressures to be generated. The purpose of this study is to supply a geometry-independent model of such a microactuator through the implementation of a fluid model rather than a solid one, which has been utilized in previous studies. Numerical simulations are conducted at different frequencies of the heating source and for different geometries of the microactuator. The results are compared with the empirical data obtained on a close to identical paraffin microactuator, which clearly show the advantages of a fluid model instead of a solid-state approximation.

A facile gravity-induced sliding droplets method is reported for deposition of nanoliter sized droplets on hydrophilic/superhydrophobic patterned surface. The deposition process is parallel where multiple different liquids can be deposited simultaneously. The process is also high-throughput, having a great potential to be scaled up by increasing the size of the substrate.

Soft micro devices and stretchable electronics have attracted great interest for their potential applications in sensory skins and wearable bio-integrated devices. One of the most important steps in building printed circuits is the alignment of assembled micro objects. Previously, the capillary self-alignment of microchips driven by surface tension effects has been shown to be able to achieve high-throughput and high-precision in the integration of micro parts on rigid hydrophilic/superhydrophobic patterned surfaces. In this paper, the self-alignment of microchips on a patterned soft and stretchable substrate, which consists of hydrophilic pads surrounded by a superhydrophobic polydimethylsiloxane (PDMS) background, is demonstrated for the first time. A simple process has been developed for making superhydrophobic soft surface by replicating nanostructures of black silicon onto a PDMS surface. Different kinds of PDMS have been investigated, and the parameters for fabricating superhydrophobic PDMS have been optimized. A self-alignment strategy has been proposed that can result in reliable self-alignment on a soft PDMS substrate. Our results show that capillary self-alignment has great potential for building soft printed circuits.

In shifting market conditions, the choice of supply chain strategies is critical when competing to serve customers (Gattorna, 2010). It is accepted in theory that the “one size fits all” approach to supply chain design is no longer valid (Christopher et al., 2006; Gattorna, 2010; Ericsson, 2011; Godsell et al., 2011). Still organisations, even in the highly competitive e-commerce market, utilise a “one size fits all” strategy to create and deliver value to their consumers, thereby implicitly assuming that consumers’ demands and buying behaviour are homogeneous, and therefore, there is no profitable reason to differentiate delivery in terms of service.