The Single-Electron Bipolar Avalanche Transistor

We present a new electronic device – the single-electron bipolar avalanche transistor (SEBAT) – which allows for the detection of single charges with a bandwidth typically above 1 GHz, exceeding by far the bandwidth of other room-temperature single-electron detectors. To the best of our knowledge, it is also the first single-electron detector to be realized in a standard CMOS technology. The device is a bipolar transistor optimized for operation in the Geiger mode. Single electrons injected through the base-emitter junction trigger the avalanche breakdown of the collector-base junction, which is rapidly stopped by a quenching circuit connected to the collector. This cycle produces a quasi-digital voltage pulse which corresponds to the detection of a single electron. The intrinsic randomness of single-electron injection associated with its particular output signal make this transistor a truly probabilistic device, in that the input parameters do not deterministically control the output, but only the likelyhood of a digital pulse. A similarly pulsed operation is also characteristic of the behavior of some neurons, with which the SEBAT shares important properties. Because of the intrinsic randomness of the pulse generation process, the SEBAT allows reconstructing the power spectrum of an input function independent of the pulse rate. Therefore, it provides access to information over its full bandwidth at extremely low power consumptions, on the order of a few nW. The randomness of the single charge injection can also be used as an entropy source for a quantum random number generator. Moreover, the non-linear input characteristics of the SEBAT enable signal mixing or pulse coincidence detection

Semiconductor device for measuring ultra small electrical currents and small voltages

A semiconductor device for measuring ultra low currents down to the level of single electrons or low voltages comprises a first and a second voltage supply terminal (1, 2), an input terminal (3) for receiving an electrical current or being supplied with a voltage to be measured, a bipolar transistor (5) having a base (B), an emitter (E) and a collector (C), wherein a first PN junction is formed between the base and the collector and a second PN junction is formed between the base and the emitter, wherein the emitter is coupled to the input terminal and the base is coupled to the second voltage supply terminal, and wherein the first PN junction is designed for reverse biased operation as an avalanche diode, and a quenching and recharging circuit (6) having a first terminal (7) coupled to the first voltage supply terminal and a second terminal (8) coupled to the collector (C) of the bipolar transistor (5), the quenching and recharging circuit permitting operation of the first PN junction reverse biased above the breakdown voltage of the first PN junction

Current and voltage ADC using a differential pair of single-electron bipolar avalanche transistors

Single-electron bipolar avalanche transistors (SEBATs) enable current sensing by electron counting at room temperature. Here, differential SEBAT circuits combining the functions of amplification and analog-to-digital (A/D) conversion are proposed and characterized for two applications: Low-current AID conversion and differential voltage A/D conversion. Charge detection efficiencies in the order of 30% are reached, allowing for the direct A/D conversion of currents in the 10(-13) A range. An equivalent of the differential pair is used as a differential voltage ADC

Direct part density inspection in laser powder bed fusion using eddy current testing

The direct qualification of additively manufactured (AM) metal components fabricated by laser powder bed fusion (LPBF), or the certification of the corresponding AM processes, remains a challenge due to the many influencing parameters, and process-inherent variability. Hence, components lack consistent quality regarding dimensional accuracy, surface quality, and material integrity, since internal defects such as pores and cracks are typical characteristics of such components. Different sensing technologies such as melt-pool monitoring are considered for in-process material integrity assessment, and for process control. However, although melt-pool monitoring provides process related information on the laser-material interaction such as melt-pool temperature and size, it does only indirectly provide sufficient information on the quality and integrity of the layer-wise generated material. Eddy current testing (ECT) is a well-established NDT technique for part quality inspection in many industries, and specifically suited to detect near-surface material defects such as e.g. cracks. This characteristic makes ECT a promising monitoring technology for the layer-wise monitoring of material quality in AM processes. Its integration into a LPBF-machine allows to generate direct material integrity data while the layer-wise acquisition offers potentials to monitor the individual part quality over a full build process, minimizing thereby post-process quality assessment measures. The basic feasibility of an ECT system to directly measure part density demonstrated, using LPBF processed SS316L samples with different densities

In-situ monitoring of powder bed fusion of metals using eddy current testing

Powder bed fusion of metals (PBF-LB/M) is the most commonly used additive manufacturing process for the layerwise production of metal parts. Although the technology has developed rapidly in recent years, manufactured parts still lack consistent quality primarily owing to process-inherent variability, and the lack of effective sensing technologies enabling the ability to control the process during part production. Thus, there are high costs caused by rigorous post-process part inspection steps required to provide compliant part certificates. In contrast to typically deployed in-situ sensing technologies, eddy current testing (ECT) is a standardized nondestructive testing (NDT) technique able to provide compliant part certificates during post-process inspection according to existing standards. This study investigates the potential of ECT as an in-situ process monitoring technology for PBF-LB/M. Parts made from AlSi10Mg were manufactured on a PBF-LB/M machine using different process parameters yielding different relative densities ranging from 99%– 99.7%. During the build cycle, the parts were measured layer-by-layer with an ECT system mounted on the machine recoater. Signal analysis methods were developed which effectively separate and calibrate the electrical conductivity component (relative electrical conductivity) and the distance component (lift-off) of the ECT signals. The relative electrical conductivity was then compared to X-ray micro-computed tomography (μCT) measurement data demonstrating that layer-to-layer differences in relative density of about 0.1% can be successfully detected via ECT. In addition, the lift-off was used to monitor the thickness of the consolidated layers and the layer-to-layer part height. The results show that ECT is an effective technology for in-situ monitoring of the relative part density paving the way for deploying ECT for in-situ NDT of PBF-LB/M-manufactured parts.ISSN:2214-860

Influence of part temperature on in-situ monitoring of powder bed fusion of metals using eddy current testing

Powder bed fusion of metals (PBF-LB/M) is currently the most widely adopted additive manufacturing technology for the fabrication of metal parts. However, the inconsistent quality of PBF-LB/M-manufactured parts and high costs for part certification are impeding wider industrial adoption. In-situ monitoring technologies are expected to enable process control in order to ensure consistent quality, and to replace some of the post-process inspection steps, therefore, reducing part certification costs. Eddy current testing (ECT) is a standardized nondestructive testing technique, which can be used as an in-situ monitoring technology to measure the part quality during the PBF-LB/M build cycle. However, the process-induced complex temperature fields in PBF-LB/M parts during the build cycle are among the most relevant disturbances due to the temperature dependence of the electrical conductivity. This study investigates the process-induced temperature influence on in-situ monitoring of relative density using ECT. Parts made from AlSi10Mg were manufactured on a PBF-LB/M machine and the build cycle was monitored using ECT and an infrared camera, which was used to extract the part surface temperature right before the ECT measurement. The results demonstrate that the temperature increase of the parts during the build cycle decreases the electrical conductivity independently of the relative part density, which was measured via micro-computed tomography. Therefore, a temperature compensation method was proposed and applied demonstrating that a layer-to-layer difference of 0.15 % relative density can be detected via ECT. Consequently, it has been demonstrated that ECT is an effective in-situ monitoring technology for PBF-LB/M, even in the presence of temperature disparities within parts.ISSN:2363-951

Relative Density Measurement of PBF-Manufactured 316L and AlSi10Mg Samples via Eddy Current Testing

Powder bed fusion (PBF) is the most commonly used additive manufacturing process for fabricating complex metal parts via the layer-wise melting of powder. Despite the tremendous recent technological development of PBF, manufactured parts still lack consistent quality in terms of part properties such as dimensional accuracy, surface roughness, or relative density. In addition to process-inherent variability, this is mainly owing to a knowledge gap in the understanding of process influences and the inability to adequately control them during part production. Eddy current testing (ECT) is a well-established nondestructive testing technique primarily used to detect near-surface defects and measure material properties such as electrical conductivity in metal parts. Hence, it is an appropriate technology for the layer-wise measuring of the material properties of the fused material in PBF. This study evaluates ECT’s potential as a novel in situ monitoring technology for relative part density in PBF. Parts made from SS316L and AlSi10Mg with different densities are manufactured on a PBF machine. These parts are subsequently measured using ECT, as well as the resulting signals correlated with the relative part density. The results indicate a statistically significant and strong correlation (316L: r(8) = 0.998, p < 0.001, AlSi10Mg: r(8) = 0.992, p < 0.001) between relative part density and the ECT signal component, which is mainly affected by the electrical conductivity of the part. The results indicate that ECT has the potential to evolve into an effective technology for the layer-wise measuring of relative part density during the PBF process.ISSN:2075-470

Microfluidic sensor and method for obtaining such a sensor

The invention describes a method for producing hybrid microelectronic/microfluidic sensors at industrial scale. The method is characterized in that it comprises the following steps for obtaining said microfluidic channel: a) a first lamination step of a dry film resist onto a PCB panel; b) a photostructuration step of the dry film resist on the PCB panel; and c) a closure step of the photostructured dry film resist to obtain the microfluidic channel. The method adapts standard PCB manufacturing processes used at industrial level by repeating some of the passages thereof, in order to produce microfluidic channels built-in with the microelectronic components in the form of a photostructured dry film resist laminated on a previously obtained PCB panel. The microchannels are moreover simply integrated in the final sensors via standardized design rules and tools used in industrial PCB manufacturing. Microelectronic/microfluidic sensors obtainable by the presently invented method are also herein disclosed

A Truly Redundant Aerial Manipulator System with Application to Push-and-Slide Inspection in Industrial Plants

International audienceWe present the design, motion planning and control of an aerial manipulator for non-trivial physical interaction tasks, such as pushing while sliding on curved surfaces – a task which is motivated by the increasing interest in autonomous non-destructive tests for industrial plants. The proposed aerial manipulator consists of a multidirectional-thrust aerial vehicle – to enhance physical interaction capabilities – endowed with a 2-DoFs lightweight arm – to enlarge its workspace. This combination makes it a truly-redundant manipulator going beyond standard aerial manipulators based on collinear multi-rotor platforms. The controller is based on a PID method with a ‘displaced’ positional part that ensures asymptotic stability despite the arm elasticity. A kinodynamic task-constrained and control-aware global motion planner is used. Experiments show that the proposed aerial manipulator system, equipped with an Eddy Current probe, is able to scan a metallic pipe sliding the sensor over its surface and preserving the contact. From the measures, a weld on the pipe is successfully detected and mapped