https://www.mdpi.com/2079-6374/9/2/65/pdf

An Alternative Medical Diagnosis Method: Biosensors for Virus Detection.

Due to the technological advances, sensors have found a significant role in different aspects of human life. The sensors have been fabricated via various manufacturing processes. Recently, additive manufacturing (AM) has become a common method for fabrication of a wide range of engineering components in many industries. This manufacturing method, commonly known as three-dimensional (3D) printing is based on melting and solidification that leads to production of a component with high dimensional accuracy and smooth surface finish. As precision and elegant techniques are needed in manufacturing of the sensors, AM has been utilized in fabrication of these parts in the last few years. In this study, we summarized and classified applications of different AM methods in manufacturing of sensors. In this context, we briefly reviewed and compared AM techniques and categorized 3D-printed sensors based on their applications. Moreover, fabrication of sensors via AM is explained in details, challenges and future prospect of this manufacturing process are discussed. Investigations on the performed studies proved that higher printing resolution, faster speed and higher efficiency are needed to reach a remarkable advance in the production of 3D-printed sensors. The presented data can be utilized not only for comparison, improvement and optimization of fabrication processes, but also is beneficial for next research in production of highly sensitive sensors.

3D-printed sensors: Current progress and future challenges

The multifaceted role of biological membranes prompted early the development of artificial lipid-based models with a primary view of reconstituting the natural functions in vitro so as to study and exploit chemoreception for sensor engineering. Over the years, a fair amount of knowledge on the artificial lipid membranes, as both, suspended or supported lipid films and liposomes, has been disseminated and has helped to diversify and expand initial scopes. Artificial lipid membranes can be constructed by several methods, stabilized by various means, functionalized in a variety of ways, experimented upon intensively, and broadly utilized in sensor development, drug testing, drug discovery or as molecular tools and research probes for elucidating the mechanics and the mechanisms of biological membranes. This paper reviews the state-of-the-art, discusses the diversity of applications, and presents future perspectives. The newly-introduced field of artificial cells further broadens the applicability of artificial membranes in studying the evolution of life.

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Artificial Lipid Membranes: Past, Present, and Future

In this paper, we propose a set of novel tactile descriptors to enable robotic systems to extract robust tactile information during tactile object explorations, regardless of the number of the tactile sensors, sensing technologies, type of exploratory movements, and duration of the objects’ surface exploration. The performance and robustness of the tactile descriptors are verified by testing on four different sensing technologies (dynamic pressure sensors, accelerometers, capacitive sensors, and impedance electrode arrays) with two robotic platforms (one anthropomorphic hand and one humanoid), and with a large set of objects and materials. Using our proposed tactile descriptors, the Shadow Hand, which has multimodal robotic skin on its fingertips, successfully classified 120 materials (100% accuracy) and 30 in-hand objects (98% accuracy) with regular and irregular textural structure by executing human-like active exploratory movements on their surface. The robustness of the proposed descriptors was assessed further during the large object discrimination with a humanoid. With a large sensing area on its upper body, the humanoid classified 120 large objects with multiple weights and various textures while the objects slid between its sensitive hands, arms, and chest. The achieved 90% recognition rate shows that the proposed tactile descriptors provided robust tactile information from the large number of tactile signals for identifying large objects via their surface texture regardless of their weight.

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Robust Tactile Descriptors for Discriminating Objects From Textural Properties via Artificial Robotic Skin

In this paper, we proposed a design to increase the sensitivity of a piezoresistive-type triaxial tactile sensor. Using conventional piezoresistive tactile sensors, in which the piezoresistive elements were completely embedded inside an elastic block, our proposed tactile sensor design features an air cavity underneath the piezoresistive elements. The cavity was created by pressing an elastic cap with microstructures onto the piezoresistive cantilevers of a sensor chip. We confirmed that the proposed design increased the sensitivity of the tactile sensor by approximately 150 times and 100 times in response to normal and lateral forces, respectively.

High-sensitivity triaxial tactile sensor with elastic microstructures pressing on piezoresistive cantilevers

A tactile sensor consisting of microcantilevers has been fabricated using the NiCr-thin-film strain gauge with low noise by surface micromachining and the slippage has been detected by using the fabricated tactile sensor array. The NiCr alloy thin film of Cr: 75 wt% has very low temperature coefficient of resistance (TCR) and is employed to suppress the temperature noise and drift. The fabricated tactile sensor with the NiCr thin film (Cr: 75 wt%) has linear dependencies of the resistance on normal and shear forces, and shows lower noise and temperature drift than that with conventional NiCr (Cr: 20 wt%) film. Normal and shear forces measured by fabricated sensor well coincide with applied forces with errors of 3–3.5 kPa. Moreover, the gripping status of the robotic hand was detected by using fabricated tactile sensor array, and the slipping condition can be judged at the rate of 76.5%.

Tactile sensor array using microcantilever with nickel–chromium alloy thin film of low temperature coefficient of resistance and its application to slippage detection

A multimodal sensor with Si micro-cantilever embedded in PDMS elastomer for measurement of proximity and touch forces has been fabricated and characterized. DC resistance of the strain gauge on the cantilever changes in proportion to the indentation depth of the object. On the other hand, the AC (> 0.5 MHz) impedance including photo-sensitive component of Si increases with increase of distance between the sensor surface and the object because of decrease of light intensity reflected on the object surface. Moreover, the AC impedance is different between grounding and floating of the proximate object because of difference of distribution of electrostatic field between electrodes, so that it is suggested that proximity can be detected as the impedance change by light as well as the electric field.

Multimodal measurement of proximity and touch force by light- and strain-sensitive multifunctional MEMS sensor

We have newly evaluated the interaction of lipid membrane with two different proteins of lysozyme and carbonic anhydrase from bovine (CAB) using a micro cantilever-based liposome biosensor with a new droplet-sealing structure. Herein 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) liposomes are used as model lipid membrane and are immobilized on the surface of cantilever. The interaction of DPPC liposome with the target protein causes deflection of the micro-cantilever, which can stably be detected by measuring the resistance change of the strain gauge. The resistance change dependent on time is used to evaluate the characteristic of liposome-protein interaction. The resistance of the cantilever-based biosensor increases monotonously with time in both of the two protein solutions. Especially, chronological resistance change depends markedly on both the concentration and species of target proteins. Finally, these results lead us to conclude that the cantilever-based liposome biosensor with the droplet-sealing structure facilitates the characterization of protein-membrane interaction. It also means that this biosensor is a promising candidate device for label-free detection of concentration and species of different target proteins.

A Micromechanical Cantilever‐Based Liposome Biosensor for Characterization of Protein‐Membrane Interaction

A micro-cantilever with thermally stable strain gauge of a NiCr thin film and a self-assembled monolayer was fabricated by surface micromachining. Liposomes, as biosensing molecules, were immobilized on its surface. To prevent evaporation of the water solvent, a reservoir made of polydimethylsiloxane around the micro-cantilever was fabricated and covered with a glass plate. The resistance of the strain gauge increases with time in the amyloid beta ( $\text{A}\beta $ ) solution, because the cantilever is bent downward caused by interaction between $\text{A}\beta $ and liposomes immobilized on the micro-cantilever surface. Moreover, resistance change depends on the interaction ability of $\text{A}\beta $ proteins with liposomes. It is therefore indicated that the fabricated static mode micro-cantilever sensor with immobilized liposomes can be used to detect $\text{A}\beta $ proteins.

Detection of Amyloid Beta Fibril Growth by Liposome-Immobilized Micro-Cantilever With NiCr Thin-Film Strain Gauge

The dynamic behavior of amyloid-beta protein (Aβ) fibrillization on cell membrane is closely related to the progression of Alzheimer’s disease (AD). In this paper, we reports a new approach for real-time monitoring of the fibrillization process of Aβ on lipid membrane using a miniaturized cantilever-based liposome biosensor, which contributes to the technology development of Aβ label-free detection and the mechanism elucidation of Aβ fibrillization on cell membrane. 1,2-Dipalmitoyl-sn- glycero -3-phosphocholine (DPPC) liposome as model cell membrane was immobilized on the cantilever surface and Aβ(1–40) was selected as a target protein in this work. Liposome-Aβ interaction is evaluated by detecting the resistance change rate of the strain gauge embedded in the cantilever, which is directly proportional to the deflection of cantilever. 24-h real-time monitoring result clearly shows chronological change in the resistance with the progress of Aβ fibrillization on liposomes. Moreover, it is found that the extent of liposome-Aβ interaction is closely dependent on the aggregate state and concentration of Aβ but is less dependent on the type of used solvent (water or serum). It is indicated that DPPC liposome shows sufficient affinity and selectivity to Aβ even in serum. In particular, a concentration of Aβ as low as 1 μM can be detected using the cantilever-based liposome biosensor. Furthermore, it is confirmed that this biosensor has a potential of recognizing different states of Aβ. We expect that the cantilever-based liposome biosensor becomes an effective tool for accelerating amyloid related research and developing the early diagnosis approach of AD.

Real-time characterization of fibrillization process of amyloid-beta on phospholipid membrane using a new label-free detection technique based on a cantilever-based liposome biosensor

Masayuki Sohgawa

Papers

Tactile sensor array using microcantilever with nickel–chromium alloy thin film of low temperature coefficient of resistance and its application to slippage detection

Multimodal measurement of proximity and touch force by light- and strain-sensitive multifunctional MEMS sensor

A Micromechanical Cantilever‐Based Liposome Biosensor for Characterization of Protein‐Membrane Interaction

Detection of Amyloid Beta Fibril Growth by Liposome-Immobilized Micro-Cantilever With NiCr Thin-Film Strain Gauge

Real-time characterization of fibrillization process of amyloid-beta on phospholipid membrane using a new label-free detection technique based on a cantilever-based liposome biosensor