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This paper aims to exploit shape-memory polymers as self-healable materials. The underlying mechanism involved the thermal transitions as well as the enrichment of the healing reagents and the closure of the crack surfaces due to shape recovery. The multi-stimuli-triggered shape memory composite was capable of self-healing under not only direct thermal but also electrical stimulations.

The shape memory epoxy polymer composites comprising the AgNWs and poly (ε-caprolactone) were fabricated by dry transfer process. The morphologies of the composites were investigated by the optical microscope and scanning electron microscopy (SEM). The electrical conduction and the Joule heating effect were measured. Furthermore, the healing efficiency under the different stimuli was calculated, whose dependence on the compositions was also discussed.

The AgNWs network maintained most of the pathways for the electrons transportation after the dry transfer process, leading to a superior conduction and flexibility. Consequently, the composites could trigger the healing within several minutes, as applied with relatively low voltages. It was found that the composites having more the AgNWs content had better electrically triggered performance, while 50 per cent poly (ε-caprolactone) content endowed the materials with max healing efficiency under thermal or electrical stimuli.

The findings may greatly benefit the application of the intelligent polymers in the fields of the multifunctional flexible electronics.

Most studies have by far emphasized on the direct thermal triggered cases. Herein, a novel, flexible and conductive shape memory-based composite, which was capable of self-healing under the thermal or electrical stimulations, has been proposed.

The purpose of this paper is to present a five-fingered, multisensory prosthetic hand integrating both intuitive myoelectric control and sensory feedback.

The artificial hand’s palm has a three-arcuate configuration and the thumb can move along a cone surface, improving the resemblance with the biological hand. By using a coupling linkage mechanism, each finger is independently actuated by a direct current motor. Both torque and position sensors are embedded in the finger to sense the hand’s status and its interaction with the outer environment. The proposed human-in-the-loop control system consists of an internal motion control scheme and an external human–machine interface. The pattern recognition-based electromyography (EMG) control scheme is adopted to control the motion of the hand, and the transcutaneous electrical nerve stimulation (TENS) is utilized to feedback the hand’s sensory information to its user.

The hand prototype shows that it has an anthropomorphic appearance (85 per cent to an average human hand), low weight (420 g), great power (10 N on the fingertip) and eligible dexterity. Clinical evaluation of the prosthetic hand on transradial amputees also approves the hand design.

From a systematic view, the paper details the design concepts of the HIT–DLR prosthetic hand IV, especially on its appearance, mechanism, myoelectric control and sensory feedback.

Chapter 3 examines the attributes of an external stimulus, which the brain collects and models to construct a sensation. An important aspect of this process is the sensory system's filtering capacity, which removes extraneous and irrelevant information from the modeled information. The response mechanisms of all five senses are discussed to establish the practice of viewing the discipline (psychophysics) from multiple perspectives (senses). The differences in multiple perspectives on the same data is compiled into a model of the attributes to which the brain attends to engage with a sensation.

Additive manufacturing has rapidly developed in terms of technology and its application in various types of industries. With this rapid development, there has been significant research in the area of materials. This has led to the invention of Smart Materials (SMs). The 4D printing is basically 3D printing of these SMs. This paper aims to focus on novel materials and their useful application in various industries using the technology of 4D printing.

Research studies in 4D printing have increased since the time when this idea was first introduced in the year 2013. The present research study will deeply focus on the introduction to 4D printing, types of SMs and its application based on the various types of stimulus. The application of each type of SM has been explained along with its functioning with respect to the stimulus.

SMs have multiple functional applications pertaining to appropriate industries. The 4D printed parts have a distinctive capability to change its shape and self-assembly to carry out a specific function according to the requirement. Afterward, the fabricated part can recover to its 3D printed “memorized” shape once it is triggered by the stimulus.

The present study highlights the various capabilities of SMs, which is used as a raw material in 4D printing.

A novel model of the upper arm under transcutaneous electrical stimulation with multi-pad electrodes is presented and experimentally validated. The model aims at simulating and analysing the effects of surface electrical stimulation on biceps brachii. The paper aims to discuss these issues.

Both the passive properties of tissues surrounding nerve bundles and the active characteristics of the nervous system are included. The output of the proposed model is nerve recruitment and muscle contraction.

Simulations and experimental tests on six healthy young adults have been conducted and results show that the proposed model gives information on electrically elicited muscle contraction in accordance with in-vivo tests and literature on motor unit recruitment order. Tests with different electrodes configurations show that the spatial distribution of active electrodes is a critical factor in electrically elicited muscle contractions, and that multi-pad electrodes can optimise the stimulation effectiveness and patient comfort with sequences of biphasic pulses of 350 μs at 30 pulses/s and threshold values of 2 mA.

Results encourage the use of the proposed model of the upper arm as a valid and viable solution for predicting the behaviour of the neuromuscular system when surface electrical stimulation is applied, thus optimising the design of neuroprosthetics.

Medical electronics has its origins in basic physiological research, a field in which there has been a continual searching since the early years of the last century for instruments capable of detecting and measuring the electric currents which accompany the activity of nerve and muscle fibres (Fig. 1). The discovery of the magnetic effects of a current by Oersted in 1819 was followed by the invention of the tangent galvanometer by Schweigger in 1820, and the moving coil galvanometer by Sturgeon in 1836. Both types of instrument were used by physiologists but they were insensitive and slow in response. Bernstein's work, published in 1871, was a classic example of the victory of ingenuity over the limitations of a sluggish measuring instrument. He employed what we should now call a ballistic galvanometer in series with electrodes attached to a frog's muscle and a special switch. This switch applied a momentary electrical stimulus to the muscle, and then closed the circuit to the galvanometer after a predetermined time interval. By varying this time interval and repeating the stimulus, Bernstein laboriously built up a graph of the current against time. His curve was sur‐prisingly similar to those obtained today using electronic recording techniques (Fig. 1b). The duration of the action current, as it was called, was a few milli‐seconds. Bernstein was able to show further that the action current was pro‐pagated along the muscle fibres with a velocity of the order of 1 metre per second.

It was established way back in the middle of the last century that the sensory organs responsible for our appreciation of taste, as distinct from that of flavour, are located on the tongue. Since then considerable research has been carried out into the structure and mechanisms involved. It has long been recognised that the prime organs of taste are the taste buds. This name was originally applied to special cells which had been observed in the mouths of fishes. Early research soon established that certain raised portions, distributed over the surface of the tongue, the papillae as they became called, are the site of the receptor organs and that those areas of the tongue which do not bear the papillae are insensitive to the taste stimulus.

Electric fields (EFs) are known to influence cell and tissue activity. This influence can be due to thermal or non-thermal effects. While the non-thermal effects are still matter of discussion, thermal effects might be detrimental for cell and tissue viability due to thermal damage, this fact being exploited by applications like hyperthermia and tissue ablation. The paper aims to discuss these issues.

In this work the authors investigate the influence of thermal damage in the consolidation of bone formation during electrostimulation (ES). The authors introduce a mathematical model describing the migration of osteoprogenitor cells, the thermal variation, the thermal damage accumulation and the formation of new bone matrix in an injury (fracture) site.

Numerical results are in agreement with experimental data and show that EFs more intense than 7.5 V/cm are detrimental for the viability of osteoprogenitor cells and the formation of new bone.

The model is suitable to conduct dosimetry studies in support of other different ES techniques aimed at improving bone and soft tissues repair.

This paper aims to create and to study multifunctional shape memory polymer (SMP) composites having temperature-sensing and actuating capabilities by embedding thermochromic particles within the polymer matrix.

The multifunctional materials were fabricated following a process consisting of blending (of the thermochromic particles and the SMP at various ratios), mixing, degasing, moulding and thermal curing, prepared by incorporating thermochromic particles within the polymer. The effect of the thermochromic particles on the thermomechanical properties and thermally responsive shape memory effect of the resulting multifunction SMP composites were characterised and interpreted.

It was found that exposure of the composites to temperatures above 70°C led to a pronounced change of their colour that was recorded by the thermal and electrical actuation approaches and was reproducibly reversible. It was also found that the colour of the composites was independent of the mechanical state of the SMP. Such effects enabled monitoring of the onset of the set/release temperature of the SMP matrix. Furthermore, the combination of thermochromic additive and the SMP resulted in significantly improved thermomechanical strength, absorption of infrared radiation and the temperature distribution of the SMP composites.

The temperature-sensing and actuating capabilities of the polymeric shape memory composites developed through this study will help to extend the field of potential applications of such composites to fields including sensors, actuators, security labels and information dissemination, where colour indication is an advantageous feature.

The SMP composites capable of temperature sensing and actuating are novel.

Over the years, electrical stimulation in drug delivery system holds particular interest in producing spatially and temporally controlled release mechanism. These systems helped in localized doses drugs to be administrated and response efficiently at target site to achieve excellent healing effect in control microenvironment. Extensive research is needed in order to develop versatile electroactive biomaterials in the field of therapeutics applications. This paper aims to discuss this issue.

This work reports the development of polycaprolactone (PCL) electrospun coated with pectin/polyaniline (PANi) composite, which has been characterized and whose drug delivery application is ascertained. The composite has been characterized on its mechanical conductivity and wettability properties to evaluate best formulation. The analysis on morphological properties using scanning electron microscope (SEM) confirmed the formation of the dual-layer electro-responsive composite.

Among different formulations studied, the pectin/PANi composition (12 percent/3 percent) was found to be an optimized composition with ultimate tensile strength of 55.48±0.65 MPa and modulus strength of 63.30±0.43 MPa with 2.41×10^–3 Scm⁻¹ electrical percolation. The hydrophobic PCL electrospun reduced as coating material was introduced on top with optimum of 85.3 percent degree of swelling and water contact angle at 39.17±0.67°. SEM micrograph revealed strong interaction between dual-layer structures with interconnected porous of uniform fibers.

Overall, these data present a multiangle initial characterization of this novel dual-layer electro-responsive composite for applications in drug delivery. However, additional analysis should be performed in order to provide a clear verification as drug delivery scaffold.