A novel cost-effective flexible microwave sensor is proposed to facilitate point-of-care testing (POCT) methods for medical diagnosis. The sensor is based on the complementary split-ring resonator (CSRR) for accurate measurement of the permittivity of biomaterials. Using this method, the measurement of the permittivity over a wide range of frequencies can be achieved. This capability can be used to characterize various materials under tests (MUT) such as blood, saliva, tissue samples, etc.. The flexibility of the proposed sensor makes it possible to use it when the accessibility of the sample has technical difficulties such as curved surfaces. Firstly, the optimized structure as well as coupling to the readout transmission line are evaluated using finite element method (FEM) simulations. Then, the prototype of the optimized structure is fabricated on thin polydimethylsiloxane (PDMS) substrate which is a biocompatible and economical polymer. Based on the simulation and experimental results, a suitable conductive material for the fabrication of CSRR and readout parts is carefully chosen. The proposed flexible sensor is tested within in-vitro setups by recording the corresponding resonant frequency and quality factor for different materials. A high correlation between the scattering parameters of the proposed sensor and the variations in materials’ characteristics which principally occurs due to the difference in their dielectric properties, is attained. Our preliminary studies have shown that such a device is capable of using in clinically acceptable zones.

Terahertz detection has attracted significant interest for noninvasive bio-imaging and security systems. Superconducting bolometers are one of the promising technologies for ultra-sensitive terahertz detection. Here, we introduce a low-cost superconducting transition-edge detector used for THz imaging. The sensing element of the detector is a meander line patterned YBa2Cu3O7-x (YBCO) thin film that realizes a monolithic superconducting bolometer. The pattern consists of 15 lines that each one of them is 1.5 mm long and 50 µm wide. This pattern is designed to have a significant response to the 0.1 THz equivalents to 3 mm wavelength radiation without any coupled antenna or separate absorber that may reduce the detection speed. 400 nm YBCO film is fabricated by the metal-organic deposition (MOD) method, an economic and scalable chemical, vacuum-free technique. The dielectric substrate of the detector is chosen to be Yttrium-stabilized Zirconia (YSZ) that has the lowest thermal conductivity between YBCO substrates resulting in a higher bolometric response. YSZ substrate needs a buffer layer to have high-quality YBCO thin film on top, so a 20 nm Ce_0.9La_0.1O₂ (CLO) buffer layer is deposited by the same MOD method. Amplitude and phase of the response of the fabricated detector to the 0.1 THz wave source, versus modulation frequency are measured and the detector is used for imaging concealed objects including cigarettes and metallic items.

Polymeric materials play an emerging role in the development of new biomedical and biosensing interfaces. Within this regard, polymer substrates can serve as a superior surface for binding and patterning of biomolecules. However, detailed information about the applicability of different polymers for surface functionalization and quantitative fluorescence microscopy is missing. Therefore, we characterized eleven different polymer foils and glass as a reference: cyclic olefin polymer (COP), cyclic olefin copolymer (COC), polymethylmethacrylate (PMMA), di-acetate, lumirror, melinex 506, melinex ST504, polyamide 6 (PA6), polyethersulfone (PES), polyether ether ketone (PEEK) and Polyimide (PI). We have recently introduced two different approaches (microcontact printing (µCP) and photolithography) for the fabrication of biomolecule micropatterns on various functionalized polymer substrates. [1, 2]. However, the implementation of photolithographic approaches for the fabrication of microstructured surfaces is expensive and labor-intensive compared to µCP. Hence, we focused on µCP for the fabrication of biomolecule micropatterns. The absence of functional groups in many polymeric materials does not allow for the immobilization of biomolecules onto these substrates by means of common surface chemistry. Therefore, we used plasma activation and wet chemistry for the introduction of functional groups on these surfaces and evaluated the coating performance via contact angle measurement and scanning electron microscopy (SEM). We gathered information about transmission and absorption properties of the different polymers via UV-VIS spectroscopy. Furthermore, we give an overview about their suitability for epifluorescence and total internal reflection fluorescence (TIRF) microscopy and evaluated these methods via contrast measurement. In addition, we tested these micropatterned polymers concerning their applicability in cell-based protein-protein interaction assays. Overall, we tested eleven different polymer substrates to evaluate their suitability for fluorescence microscopy and subcellular live cell micropatterning assays. COC, COP and PMMA turned out to be cheap and flexible alternatives to glass substrates with comparable chemical and optical properties.

References

1. Hager, R.; Haselgrübler, T.; Haas, S.; Lipp, A.-M.; Weghuber, J. Fabrication, Characterization and Application of Biomolecule Micropatterns on Cyclic Olefin Polymer (COP) Surfaces with Adjustable Contrast. Biosensors (Basel) 2019, 10, doi:10.3390/bios10010003.
2. Hager, R.; Müller, U.; Ollinger, N.; Weghuber, J.; Lanzerstorfer, P. Subcellular micropatterning for visual immunoprecipitation reveals differences in cytosolic protein complexes downstream the EGFR. bioRxiv 2021.05.25.445547; doi: https://doi.org/10.1101/2021.05.25.445547

In this work, a characterization environment for a Micro-Electro-Mechanical System (MEMS) pickup under guided ultrasonic wave (GUW) excitation is being developed. The dispersive behavior of GUW, reflections and other kinds of wave interactions, might result in a complex wave field which requires a specific analysis and interpretation of the recorded signals. This makes it difficult or impossible to interpret the sensor signal regarding the distinguishability between the sensor transfer behavior and the specific behavior of the test structure. Therefore, a proper application-suited design of the tested structure is crucial for reliable sensor characterization. The aim of this contribution is the design and evaluation of a setup that allows a representative situation for a GUW application and discusses a defined input of vibration energy at the sensor location. Parameters as the specimen’s geometry, material properties and the sensor specifications that serve the definition of the specimen setup are taken into account as well as the experimental settings of the GUW excitation. Furthermore the requirements for the test application case will be discussed.

The localization of sound sources has received increasing interest over the last decades, given its wide range of applications. The triangulation method using the Time of Arrival (ToA) of a signal has shown to be useful and easy-to-use and, at the same time, provides accurate results. In this work, the acoustic trilateration method is applied in experimental measures to study and demonstrate its precision in air. Firstly, the method is tested in an anechoic chamber (low reverberant environment) demonstrating its functionality and accuracy. The next step has been the application of the method by using a low-cost system to demonstrate how a non-anechoic environment affects the accuracy of the localization. The detection of the received signal is implemented using a cross-correlation method in the time domain for both cases. Furthermore, the influence of the number and positions of the receivers that are used for this process in the accuracy of the results is also studied.

Commercially available photopolymer resin is combined with lead zirconate titanate (PZT) micrometer size piezoelectric particles to form 3D printable suspensions that solidify under UV light. This in turn allows achieving various non-standard sensor geometries which might bring benefits, such as increased piezoelectric output in specific conditions. However, it is unclear if piezoelectric composite materials are suitable for guided ultrasonic wave (GUW) detection which is crucial for Structural Health Monitoring (SHM) in different applications. In this study, thin piezoelectric composite sensors are tape-casted, solidified under UV light, covered with electrodes, polarized in high electric field and adhesively bonded onto a waveguide. This approach helps to understand the capabilities of thin piezoelectric composite sensors for GUW detection. In a proof of concept, thin 2-dimensional rectangular and circular piezoelectric composite sensors with an effective surface area smaller than 400 mm², applied to an aluminum plate with a thickness of 2 mm, demonstrate successful detection of GUW up to 250 kHz. An analytical calculation of the maximum and minimum amplitude for the ratio of the wavelength and the sensor length in wave propagation direction shows good agreement with the sensor recorded amplitude. The output of the piezoelectric composite sensors is compared to commercial piezoelectric discs to evaluate their performance.

Science and industry have sought to develop systems aiming to avoid total failures in power transformers since these machines can be working under overloads, moisture, mechanical and thermal stresses, among others. These unconformities can promote the degradation of the insulation system and lead the transformer to total failure. In the incipient stages of these faults, it is common to detect Full Discharges (FD), which are short circuits between degraded coils. Therefore, several techniques were developed to perform FD diagnosis using UHF, acoustics, and current sensors. In this scenario, this article presents a mathematical model for Rogowski coils and compares two different types of core: ferrite and Teflon. For this purpose, FDs were induced in an oil-filled transformer. The sensibility and frequency response of the Rogowski coils were compared. This analysis was achieved using the Power Spectrum Density (PSD) and the energy of the acquired signals. Additionally, the Short-Time Fourier Transform (STFT) was applied to detect repetitive discharges. The results indicated that the ferrite core increases the sensibility by 50 times. Although the Teflon core showed low sensibility, its frequency band was concentrated between 5 MHz to 10 MHz, while ferrite presents a frequency response from 0 to 1 MHz. Therefore, Teflon-based Rogowski’s coils can be a promising alternative to low-cost monitoring systems.

Thin artificial muscle is a flexible and lightweight pneumatic actuator with 2 mm in outer diameter. It generates contractile displacement by applying pneumatic pressure. We have fabricated a string-shaped actuator called “Active string” by accumulating thin artificial muscles using the string production process. The active string is expected to be applied to mechanical systems used in medical, welfare, and agricultural fields because of its high contractile displacement/force, flexibility, and safety. However, displacement control of the active string is challenging because general bulky and rigid displacement sensors such as an encoder and a potentiometer are not suitable for the sensor element of the active string. These sensors are difficult to embed into the active string, and their rigidity interfere the advantage of the active string. Therefore, in this report, a flexible optical fiber sensor is combined with the active string to enable real-time sensing of its displacement. The optical fiber is easy to embed to the active string and does not interfere with the motion of the active string. As the active string contracts, the radius of curvature of the optical fiber decreases, and light intensity propagating in the optical fiber decreases due to bending loss. Fundamental experiments were carried out. The experimental results showed that the sensor value acquired by the embedded optical fiber sensor changed with corresponding to the displacement of the active string. It suggests that it is possible to estimate the displacement of the active string by the optical fiber sensor.

In our study, a soft robot arm consisting of McKibben artificial muscles and silicone rubber has been developed. This robot arm can perform bending and twisting motions by applying pneumatic pressure to several artificial muscles. Since the robot arm is made of flexible materials only, it has high flexibility and shape adaptability. Therefore, the soft robot arm is expected to play an active role in situations involving people and fragile objects, such as medical care, nursing care, and agricultural work. In addition, the arm-worn wearable interface has been developed as an operating system for the soft robot arm. It is made by attaching flexible strain sensors to a highly elastic arm cover worn by an operator. This interface detects the bending of the operator's wrist and the twisting of the forearm, and the detected motions are used as inputs for the bending and twisting motions of the soft robot arm. This enables the intuitive manipulation of the soft manipulator. In this report, flexible strain sensors are placed on the soft robot arm for master-slave feedback control. The number of sensors and their fundamental locations in the soft robot arm and the wearable interface are the same, and they are arranged in one-to-one correspondence. By comparing the corresponding sensor values, master-slave feedback control is realized.

To date, effective means of predicting pregnancy labour continuous to lack. Magnetic field signals from uterine contractions have shown in recent studies to be able to predict labour state with a greater accuracy when compared with existing methods. This means of labour prediction methods from magnetic field signals appears to rely on a supervised learning post-processing framework whose calibration relies on an effective labelling of the training sample set. Despite its overall effectiveness, the need for sample preparation and labelling requires external intervention which in turn demands resource allocation in a clinical setting. As a potential solution to this, using a reduced electrode channel from a Magnetomyography instrumentation, we propose a multi-stage self-sorting Cybernetic model that comprises of an ensemble of various post-processing methods and underpinned by an un-supervised learning framework which allows for an automated method towards learning from the trend in the data to use to infer labour state and immanency. The results showed a comparable accuracy with that from a supervised learning method from a prior study and has produced an architecture of how an intelligent Cybernetic model can be used for labour prediction and cost saving benefits within a clinical setting.