Artificial Finger Research Articles

Biomimetic Tendon-Based Mechanism for Finger Flexion and Extension in a Soft Hand Exoskeleton: Design and Experimental Assessment.

This study proposes a bioinspired exotendon routing configuration for a tendon-based mechanism to provide finger flexion and extension that utilizes a single motor to reduce the complexity of the system. The configuration was primarily inspired by the extrinsic muscle-tendon units of the human musculoskeletal system. The function of the intrinsic muscle-tendon units was partially compensated by adding a minor modification to the configuration of the extrinsic units. The finger kinematics produced by this solution during flexion and extension were experimentally evaluated on an artificial finger and compared to that obtained using the traditional mechanism, where one exotendon was inserted at the distal phalanx. The experiments were conducted on nine healthy subjects who wore a soft exoskeleton glove equipped with the novel tendon mechanism. Contrary to the traditional approach, the proposed mechanism successfully prevented the hyperextension of the distal interphalangeal (DIP) and the metacarpophalangeal (MCP) joints. During flexion, the DIP joint angles produced by the novel mechanism were smaller than the angles generated by the traditional approach for the same proximal interphalangeal (PIP) joint angles. This provided a flexion trajectory closer to the voluntary flexion motion and avoided straining the interphalangeal coupling between the DIP and PIP joints. Finally, the proposed solution generated similar trajectories when applied to a stiff artificial finger (simulating spasticity). The results, therefore, demonstrate that the proposed approach is indeed an effective solution for the envisioned soft hand exoskeleton system.

Improvement of Precision Grasping Performance by Interaction Between Soft Finger Pulp and Hard Nail.

In this study, we investigated the effect of the presence or absence of fingernails on precision grasping using artificial anthropomimetic fingers. We hypothesized that fingernails improve precision grasping performance by increasing the friction coefficient while suppressing fingertip deformation. To test our hypothesis, we developed artificial fingertips, each composed of bone, nail, skin, and soft tissue, and fabricated three types of artificial fingers with different skin softness grades and artificial fingers without nails as the control condition. Pullout experiments of cylindrical objects and T-shaped blocks were conducted using the developed artificial fingertips with and without nails, and the magnitude of the holding force was compared. The nail contributed to object grasping stability because the magnitude of the holding force was significantly increased by the presence of the nail in the artificial fingertip with soft skin. The rate of increase in the magnitude of the holding force of the T-shaped block was more significant (3.10 times maximum) compared with the cylindrical object (1.08 times maximum) because the finger pulp deformation was suppressed by the nail, and the form closure, that is, geometric constraint, was formed for the grasping object. The results of this study show that soft fingertips and hard nails can significantly improve the grasping performance of soft robotic hands. And these results suggest that the human nail improves precision grasping performance by forming geometric constraints on the grasped object, suppressing finger pulp deformation.

Interactions of an Artificial Zinc Finger Protein with Cd(II) and Hg(II): Competition and Metal and DNA Binding

Cys2His2 zinc finger proteins are important for living organisms, as they—among other functions—specifically recognise DNA when Zn(II) is coordinated to the proteins, stabilising their ββα secondary structure. Therefore, competition with other metal ions may alter their original function. Toxic metal ions such as Cd(II) or Hg(II) might be especially dangerous because of their similar chemical properties to Zn(II). Most competition studies carried out so far have involved small zinc finger peptides. Therefore, we have investigated the interactions of toxic metal ions with a zinc finger proteins consisting of three finger units and the consequences on the DNA binding properties of the protein. Binding of one Cd(II) per finger subunit of the protein was shown by circular dichroism spectroscopy, fluorimetry and electrospray ionisation mass spectrometry. Cd(II) stabilised a similar secondary structure to that of the Zn(II)-bound protein but with a slightly lower affinity. In contrast, Hg(II) could displace Zn(II) quantitatively (logβ′ ≥ 16.7), demolishing the secondary structure, and further Hg(II) binding was also observed. Based on electrophoretic gel mobility shift assays, the Cd(II)-bound zinc finger protein could recognise the specific DNA target sequence similarly to the Zn(II)-loaded form but with a ~0.6 log units lower stability constant, while Hg(II) could destroy DNA binding completely.

NUMBER PATTERN CALCULATOR INSTRUCTION LESSON: A TEACHERS’ MATHEMATICS CLASSROOM REFERENCE RESOURCE

This study demonstrates how number patterns can be used for calculator instructional lesson. The lesson’s strengths are reflected by teachers’ qualitative evaluation comments. The study contributes teacher learning material on calculator use for their professional development. The study is guided by qualitative case study research design utilising socio-cultural activity theory. Data were collected from the teacher’s scheme of work, observation of three 20 minutes lessons separated by 15 minutes breaks and lesson evaluation discussions from the lesson’s video by 46 mathematics teachers in five groups. The study found that: the demonstration lesson motivated participating teachers and learners to use calculators. The demonstrating teacher had a high pedagogical technology knowledge level (being proficient user of a calculator, understanding principles and techniques required to use the calculator to teach mathematics). The class environment was conducive (allowed learners to talk to each other or stand to consult a friend on the other desk). Every learner had a calculator. Demonstration charts were clear and visible from the back of the class. The teacher was enthusiastic, able to sequence content and reflect on investigative teaching methods. Teacher applied demonstration, directive, group and individual activities in the same lesson. Calculator application procedure notes on learners’ cell phones brought the teacher on the child’s side for a one-on-one tutorial. Study concluded that, calculators make mathematics exploration, experimentation and learning mathematics patterns possible and interesting. Collaborative inquiry was the framework of the lesson. Learners were motivated to learn in and out of the class. Some learners had challenges of low vision. They took time to identify [x2], [x3] and [yx] calculator keys. Those with thick fingers and ladies with long artificial finger nails pressed more than one key at a time. These experiences form assumed knowledge content for next lesson introduction.

Soft Gripper with Electro-Thermally Driven Artificial Fingers Made of Tri-layer Polymers and a Dry Adhesive Surface.

Soft grippers have attracted great interest in the soft robotics research field. Due to their lack of deformability and control over compliance, it can be challenging for them to pick up objects that are too large or too small in size. In particular, compliant objects are vulnerable to the large grasping force. Therefore, it is crucial to be able to adjust the stiffness of the gripper materials. In this study, a soft gripper consisting of three artificial fingers is reported on. Each of the artificial fingers is made of a tri-layer polymer structure. An exterior layer, made of an ecoflex-graphene composite is embedded with electric wires as a heating source, by applying direct-current potential. The Joule heat not only allows for deformation of the exterior layer, but also transfers heat to the middle layer of the thermoplastic polyurethane (TPU) elastomer. As a result, the stiffness of the TPU layer can be adjusted using electro-thermal heating. Meanwhile, the third layer consists of a polydimethylsiloxane replica as a supporting layer with a gecko-inspired dry adhesive structure. By applying voltage through electric wires, the artificial fingers can bend and, thus, the soft gripper can hold the objects, with the help of the dry adhesive layer. Finally, objects like a shuttlecock, tennis ball and a glass beaker, can be picked up by the soft gripper. This research may provide an insight for the design and fabrication of soft robotic manipulators.

Artificial tactile perception smart finger for material identification based on triboelectric sensing.

Tactile perception includes the direct response of tactile corpuscles to environmental stimuli and psychological parameters associated with brain recognition. To date, several artificial haptic-based sensing techniques can accurately measure physical stimuli. However, quantifying the psychological parameters of tactile perception to achieve texture and roughness identification remains challenging. Here, we developed a smart finger with surpassed human tactile perception, which enabled accurate identification of material type and roughness through the integration of triboelectric sensing and machine learning. In principle, as each material has different capabilities to gain or lose electrons, a unique triboelectric fingerprint output will be generated when the triboelectric sensor is in contact with the measured object. The construction of a triboelectric sensor array could further eliminate interference from the environment, and the accuracy rate of material identification was as high as 96.8%. The proposed smart finger provides the possibility to impart artificial tactile perception to manipulators or prosthetics.

Bio-Inspired Control System for Fingers Actuated by Multiple SMA Actuators

Spiking neural networks are able to control with high precision the rotation and force of single-joint robotic arms when shape memory alloy wires are used for actuation. Bio-inspired robotic arms such as anthropomorphic fingers include more junctions that are actuated simultaneously. Starting from the hypothesis that the motor cortex groups the control of multiple muscles into neural synergies, this work presents for the first time an SNN structure that is able to control a series of finger motions by activation of groups of neurons that drive the corresponding actuators in sequence. The initial motion starts when a command signal is received, while the subsequent ones are initiated based on the sensors’ output. In order to increase the biological plausibility of the control system, the finger is flexed and extended by four SMA wires connected to the phalanges as the main tendons. The results show that the artificial finger that is controlled by the SNN is able to smoothly perform several motions of the human index finger while the command signal is active. To evaluate the advantages of using SNN, we compared the finger behaviours when the SMA actuators are driven by SNN, and by a microcontroller, respectively. In addition, we designed an electronic circuit that models the sensor’s output in concordance with the SNN output.

Novel ionic bioartificial muscles based on ionically crosslinked multi-walled carbon nanotubes-mediated bacterial cellulose membranes and PEDOT:PSS electrodes

High-performance bioartificial muscles with low-cost, large bending deformation, low actuation voltage, and fast response time have drawn extensive attention as the development of human-friendly electronics in recent years. Here, we report a high-performance ionic bioartificial muscle based on the bacterial cellulose (BC)/ionic liquid (IL)/multi-walled carbon nanotubes (MWCNT) nanocomposite membrane and PEDOT:PSS electrode. The developed ionic actuator exhibits excellent electro-chemo-mechanical properties, which are ascribed to its high ionic conductivity, large specific capacitance, and ionically crosslinked structure resulting from the strong ionic interaction and physical crosslinking among BC, IL, and MWCNT. In particular, the proposed BC-IL-MWCNT (0.10 wt%) nanocomposite exhibited significant increments of Young’s modulus up to 75% and specific capacitance up to 77%, leading to 2.5 times larger bending deformation than that of the BC-IL actuator. More interestingly, bioinspired applications containing artificial soft robotic finger and grapple robot were successfully demonstrated based on high-performance BC-IL-MWCNT actuator with excellent sensitivity and controllability. Thus, the newly proposed BC-IL-MWCNT bioartificial muscle will offer a viable pathway for developing next-generation artificial muscles, soft robotics, wearable electronic products, flexible tactile devices, and biomedical instruments.

High-performance microfibrillated cellulose-based low voltage electroactive ionic artificial muscles in bioinspired applications

The development of electroactive high-performance biofriendly artificial muscles with large mechanical bending deformation, fast response time, low actuation voltage, and excellent durability is highly desirable for human friendly electronics such as soft robots, active biomedical devices, wearable devices, and flexible haptic displays. Herein, we report a novel ultralow voltage high-performance ionic artificial muscle based on microfibrillated cellulose (MFC), ionic liquid (IL) as a plasticizer, and conducting polymer poly(3,4-ethylene dioxythiophene)-polystyrene sulfonate (PEDOT: PSS) as electrodes. The proposed MFC-IL biocomposite membrane was fabricated through doping of MFC with IL. The PEDOT:PSS layers were uniformly deposited on surfaces of the MFC-IL membrane by using the dip-coating method. The designed MFC-IL actuator demonstrated a large bending strain (0.31% under a sinusoidal input voltage of ±1.5 V at 0.1 Hz), low actuation voltage (<2 V), fast response time (<2.5 s), and excellent actuation durability (98% retention for 2 h), all of which were mainly due to its relatively large specific capacitance (115.2 mF cm−2) and tuned mechanical properties, resulting from the strong ionic interactions and crosslinking of MFC fibers with IL. More importantly, bioinspired applications including the grapple robot, bionic medical stent, and artificial soft robotic finger have been successfully realized. Therefore, the newly designed MFC-IL ionic soft actuator and its bioinspired robotic designs will provide a viable way for developing next-generation artificial muscles, soft robotics, active medical devices, and flexible displays.

SARS-CoV-2 virus transfers to skin through contact with contaminated solids

Transfer of SARS-CoV-2 from solids to fingers is one step in infection via contaminated solids, and the possibility of infection from this route has driven calls for increased frequency of handwashing during the COVID-19 pandemic. To analyze this route of infection, we measured the percentage of SARS-CoV-2 that was transferred from a solid to an artificial finger. A droplet of SARS-CoV-2 suspension (1 µL) was placed on a solid, and then artificial skin was briefly pressed against the solid with a light force (3 N). Transfer from a variety of solids was detected, and transfer from the non-porous solids, glass, stainless steel, and Teflon, was substantial when the droplet was still wet. The viral titer for the finger was 13–16% or 0.8–0.9 log less than for the input droplet. Transfer still occurred after the droplet evaporated, but was smaller, 3–9%. We found a lower level of transfer from porous solids but did not find a significant effect of solid wettability for non-porous solids.

Do interoception and attending to the upper limbs affect body ownership and body representation in the grasp illusion?

Passively grasping an unseen artificial finger induces ownership over this finger and an illusory coming together of one’s index fingers: a grasp illusion. Here we determine how interoceptive ability and attending to the upper limbs influence this illusion. Participants passively grasped an unseen artificial finger with their left index finger and thumb for 3 min while their right index finger, located 12 cm below, was lightly clamped. Experiment 1 (n = 30) investigated whether the strength of the grasp illusion (perceived index finger spacing and perceived ownership) is related to a person’s level of interoceptive accuracy (modified heartbeat counting task) and sensibility (Noticing subscale of the Multidimensional Assessment of Interoceptive Awareness). Experiment 2 (n = 30) investigated the effect of providing verbal or tactile cues to guide participants’ attention to their upper limbs. On their own, neither interoceptive accuracy and sensibility or verbal and tactile cueing had an effect on the grasp illusion. However, verbal cueing increased the strength of the grasp illusion in individuals with lower interoceptive ability. Across the observed range of interoceptive accuracy and sensibility, verbal cueing decreased perceived index spacing by 5.6 cm [1.91 to 9.38] (mean [95%CI]), and perceived ownership by ∼3 points on a 7-point Likert scale (slope -0.93 [-1.72 to -0.15]). Thus, attending to the upper limbs via verbal cues increases the strength of the grasp illusion in a way that is inversely proportional to a person’s level of interoceptive accuracy and sensibility.

Flexible and stable grasping by multi-jointed pneumatic actuator mimicking the human finger-impacts of structural parameters on performance

Most current pneumatic actuators, whether they have a single inflation chamber or multiple inflation chambers, are driven by a single air source, limiting their ability to complete precise and targeted manipulation. This paper describes a flexible pneumatic actuator with a three-chamber structure to mimic the motion of a human finger. Each chamber, which mimics the finger joint, is independently driven by a pressurized air source, making the finger flexible enough to grasp an object according to its shape. To achieve a more extensive deformation with lower pressure, the finite element method (FEM) was used to optimize and determine the structural parameters of the actuator. Actuators, both with and without fiber-reinforcement, were experimentally investigated to determine the bending performance of the artificial finger when pressurized individually or simultaneously. A three-finger gripper fabricated based on the multi-jointed pneumatic actuator successfully grasps various objects with higher contact area compared to previous designs, which achieves more stable grasping. The current actuator is flexible and stable enough to be used for a wide range of objects with different dimensions, shapes, and textures by controlling the various chambers.

A User-Friendly Packaging Solution for Silicon-Based Pressure Die to Develop Prosthetic Tactile Sensing

At present, most of tactile sensors integrated in prosthetic hands are installed on the surface of the fingers, which destroys the curved and compliant nature of finger surface that is important for the manipulation of objects. To solve this problem, this paper proposes a user-friendly packaging solution with solid-liquid hybrid structure for silicon-based pressure die to develop a force sensitive artificial finger which can meet the requirements of sensor sensitivity while maintaining the geometric and mechanical features of the finger surface. The artificial finger consists of a packaging including a thumb-shaped finger stall and a certain amount of dielectric liquid, a rigid phalange, a silicon-based pressure die, a printed circuit board (PCB), and a clamp plate. When a force is applied on the pad of the artificial finger, the finger stall deforms, which compresses the liquid in the chamber and result in a resistance change of the pressure die. A prototype with the overall size of 37 mm $\times32$ mm $\times50$ mm was developed and tested. Results showed that the artificial finger has good sensing performance with force detection range of 5.7 mN to 10.5 N, sensitivity of 3.34 mV/N and 1.99 mV/N in the range of 0 - 4.0 N and 4.0 N - 10.5 N respectively, linearity of 0.99, repeatability error of 0.77%, and hysteresis error of 2.9%. Furthermore, two typical daily applications including the mouse click and the texture recognition were carried out with the prototype, proving good real-time detecting capacity and dynamic characteristic.

A Ti3C2Tx MXene-Based Energy-Harvesting Soft Actuator with Self-Powered Humidity Sensing and Real-Time Motion Tracking Capability.

A smart soft actuator with multiple capabilities of humidity-driven actuating, humidity energy harvesting, self-powered humidity sensing, and real-time motion tracking is reported. It is designed on the basis of an MXene/cellulose/polystyrene sulfonic acid (PSSA) composite membrane. This actuator is driven by asymmetric expansion under a moisture gradient during capture of the chemical potential of humidity to mechanical power. Meanwhile, the gradient moisture chemistry also induces directional proton diffusion to generate electricity with high power density and open-circuit voltage. A good linear correlation between the humidity sensitivity, electrical signal, and bending state of this actuator allows real-time tracking of motion modes with humidity change without an external power supply. This multifunctional soft actuator can be used for engineering smart switches, artificial fingers, and soft robots with trackable and distinguishable motion patterns, as well as sensitive noncontacting humidity sensor and breathing monitors.

Development of an artificial zinc finger – Luciferase fusion protein for the rapid detection of Salmonella typhimurium

A novel artificial Zinc finger – luciferase fusion protein was successfully developed for rapid detection of Salmonella typhimurium, a worldwide-distributed foodborne pathogen. The designed Zinc finger (ZF) protein bound specifically to a 12 bp region of the Salmonella spp invasion gene invA. While the luciferase from Gaussia princeps called Gaussia luciferase (Gluc) was for the first time fused with the artificial ZF domain to improve the detection sensitivity. The fusion protein successfully recognized and bound to the synthesized invA dsDNA with high specificity and sensitivity. The detection limit was as low as 10 fmol of dsNDA. Then, the bacteria PCR products were subsequently used to assess the zinc finger – luciferase fusion protein. The final results indicated that the ZF-Gluc fusion protein system could detect S. typhimurium as low as 1 CFU/mL in 2 h after the PCR. Therefore, this study provided us with a novel artificial zinc finger fusion protein and an efficient method to accomplish the rapid detection of the major foodborne pathogen S. typhimurium. In addition, the specific artificial ZF proteins that bund to particular dsDNA sequences could be easily designed, the ZF-Gluc might has broad application prospects in the field of rapid pathogenic bacteria detection.

Flexible and highly sensitive three-axis pressure sensors based on carbon nanotube/polydimethylsiloxane composite pyramid arrays

The development of flexible and sensitive three-axis pressure sensors is of great interest for various wearable applications, such as electronic skin, soft robotics, and health monitoring. This study aims to propose a highly sensitive and flexible pressure sensor that can measure three-axis pressure based on conductive microstructured carbon nanotubes (CNTs) and polydimethylsiloxane (PDMS) elastomer with a simple and large-scale fabrication method that uses a polymer wet etching process. The randomly exposed CNTs on the surface using PDMS wet etching improve the sensitivity of the pressure sensors. The fabricated sensors exhibit a high sensitivity of 1.39 kPa−1 for a pressure range of 250 Pa, excellent limit of detection capability of 1.26 Pa, fast response time of within 52 ms, and high reliability of over 10,000 times of pressure loading/unloading. As an application, the pressure sensors are demonstrated using electronic skin on human fingers for the detection of the pressure levels and pattern recognition of distributed pressure. Moreover, to measure the three-axis pressure, pressurization tests are conducted using artificial fingers, demonstrating that the fabricated sensor can successfully measure the pressures applied along the three axes.

Arabidopsis MORC proteins function in the efficient establishment of RNA directed DNA methylation

The Microrchidia (MORC) family of ATPases are required for transposable element (TE) silencing and heterochromatin condensation in plants and animals, and C. elegans MORC-1 has been shown to topologically entrap and condense DNA. In Arabidopsis thaliana, mutation of MORCs has been shown to reactivate silent methylated genes and transposons and to decondense heterochromatic chromocenters, despite only minor changes in the maintenance of DNA methylation. Here we provide the first evidence localizing Arabidopsis MORC proteins to specific regions of chromatin and find that MORC4 and MORC7 are closely co-localized with sites of RNA-directed DNA methylation (RdDM). We further show that MORC7, when tethered to DNA by an artificial zinc finger, can facilitate the establishment of RdDM. Finally, we show that MORCs are required for the efficient RdDM mediated establishment of DNA methylation and silencing of a newly integrated FWA transgene, even though morc mutations have no effect on the maintenance of preexisting methylation at the endogenous FWA gene. We propose that MORCs function as a molecular tether in RdDM complexes to reinforce RdDM activity for methylation establishment. These findings have implications for MORC protein function in a variety of other eukaryotic organisms.

Silicone and Pyrocarbon Artificial Finger Joints.

Artificial finger joint design has been developed through different stages through the past. PIP (proximal interphalangeal) and MCP (metacarpophalangeal) artificial finger joints have come to replace the amputation and arthrodesis options; although, these artificial joints are still facing challenges related to reactive tissues, reduced range of motion, and flexion and extension deficits. Swanson silicone artificial finger joints are still common due to the physician's preferability of silicone with the dorsal approach during operation. Nevertheless, other artificial finger joints such as the pyrocarbon implant arthroplasty have also drawn the interests of practitioners. Artificial finger joint has been classified under three major categories which are constrained, unconstrained, and linked design. There are also challenges such as concerns of infections and articular cartilage necrosis associated with attempted retention of vascularity. In addition, one of the main challenges facing the silicone artificial finger joints is the fracture occurring at the distal stem with the hinge. The aim of this paper is to review the different artificial finger joints in one paper as there are few old review papers about them. Further studies need to be done to develop the design and materials of the pyrocarbon and silicone implants to increase the range of motion associated with them and the fatigue life of the silicone implants.

Ectopic targeting of CG DNA methylation in Arabidopsis with the bacterial SssI methyltransferase

The ability to target epigenetic marks like DNA methylation to specific loci is important in both basic research and in crop plant engineering. However, heritability of targeted DNA methylation, how it impacts gene expression, and which epigenetic features are required for proper establishment are mostly unknown. Here, we show that targeting the CG-specific methyltransferase M.SssI with an artificial zinc finger protein can establish heritable CG methylation and silencing of a targeted locus in Arabidopsis. In addition, we observe highly heritable widespread ectopic CG methylation mainly over euchromatic regions. This hypermethylation shows little effect on transcription while it triggers a mild but significant reduction in the accumulation of H2A.Z and H3K27me3. Moreover, ectopic methylation occurs preferentially at less open chromatin that lacks positive histone marks. These results outline general principles of the heritability and interaction of CG methylation with other epigenomic features that should help guide future efforts to engineer epigenomes.

Asymmetric shape of distal phalanx of human finger improves precision grasping

In morphology field, the functions of an asymmetric-shaped distal phalanx in human finger have only been inferred. In this study, we used an engineering approach to empirically examine the effects of the shape of distal phalanx on the ability of precision grasping. Hence, we developed artificial fingertips consisting of four parts, namely bones, nails, skin, and subcutaneous tissue, that substitute the actual human fingertips. Furthermore, we proposed a method to evaluate the grasping ability of artificial fingers. When a cylindrical object was grasped by an artificial fingertip, a pull-out experiment was conducted. Thus, the asymmetric type was found to be superior in terms of drawing force, holding time, and work of friction than the symmetric type. Our results clearly demonstrate that the asymmetric shape, particularly the mirror-reversed shape of the distal phalanx, improves the ability of precision grasping and suggests that the human distal phalanx is shaped favorably for object grasping.