Myoelectric Research Articles

Innovations in surgery; bone-anchored prosthetic limbs and targeted muscle reinnervation: an update

How new technology and surgical techniques can lead to an improved patient experience.

Using eye tracking to assess learning of a multifunction prosthetic hand: an exploratory study from a rehabilitation perspective

BackgroundEye tracking technology not only reveals the acquisition of visual information at fixation but also has the potential to unveil underlying cognitive processes involved in learning to use a multifunction prosthetic hand. It also reveals gaze behaviours observed during standardized tasks and self-chosen tasks. The aim of the study was to explore the use of eye tracking to track learning progress of multifunction hands at two different time points in prosthetic rehabilitation.MethodsThree amputees received control training of a multifunction hand with new control strategy. Detailed description of control training was collected first. They wore Tobii Pro2 eye-tracking glasses and performed a set of standardized tasks (required to switch to different grips for each task) after one day of training and at one-year-follow-up (missing data for Subject 3 at the follow up due to socket problem). They also performed a self-chosen task (free to use any grip for any object) and were instructed to perform the task in a way how they would normally do at home. The gaze-overlaid videos were analysed using the Tobii Pro Lab and the following metrics were extracted: fixation duration, saccade amplitude, eye-hand latency, fixation count and time to first fixation.ResultsDuring control training, the subjects learned 3 to 4 grips. Some grips were easier, and others were more difficult because they forgot or were confused with the switching strategies. At the one-year-follow-up, a decrease in performance time, fixation duration, eye-hand latency, and fixation count was observed in Subject 1 and 2, indicating an improvement in the ability to control the multifunction hand and a reduction of cognitive load. An increase in saccade amplitude was observed in both subjects, suggesting a decrease in difficulty to control the prosthetic hand. During the standardized tasks, the first fixation of all three subjects were on the multifunction hand in all objects. During the self-chosen tasks, the first fixations were mostly on the objects first.ConclusionThe qualitative data from control training and the quantitative eye tracking data from clinical standardized tasks provided a rich exploration of cognitive processing in learning to control a multifunction hand. Many prosthesis users prefer multifunction hands and with this study we have demonstrated that a targeted prosthetic training protocol with reliable assessment methods will help to lay the foundation for measuring functional benefits of multifunction hands.

Exploring the effects of increased socket-residual limb coupling integrity via vacuum assisted suspension on prosthetic control: a preliminary study in transtibial prosthesis users.

The prosthetic socket provides the critical interface between prosthesis and residuum. The purpose of this pilot study was to explore the effect of altering socket-residuum coupling integrity on limb and body control, through the use of vacuum-assisted suspension. A secondary purpose was to explore the potential use of two measurement tools designed to assess mobility in a clinical context. Individuals with unilateral transtibial amputation performed intentional sway (n = 7) and treadmill walking (n = 6) tasks at three vacuum levels. Sway deviation from a straight-line path to peripheral targets was measured using an instrumented balance platform. Step width variability and targeting accuracy were measured using an augmented reality treadmill. There was a significant difference in intentional sway performance toward the target on the anterior diagonal toward the prosthetic side (p = 0.036); higher vacuum levels tended toward less deviation from a straight-line path. We found no group differences between total intentional sway deviation, step width variability or stepping accuracy across vacuum levels. Improved socket-residuum coupling integrity via vacuum may have measurable effects on functional control that warrant further investigation. We highlight limitations of the clinical testing paradigms to inform future work.Implications for rehabilitationThe fit of the socket is a critical factor in the success of lower limb prosthesis use.Vacuum-assisted suspension modifies the coupling between the residuum and socket.Changes in socket-residuum coupling may lead to measurable differences in control; however, these may be activity and person-specific.Clinically intended instrumented tests of movement function derived for an intact anatomy should be used with caution when assessing prosthesis users.

Characterization of a conductive hydrogel@Carbon fibers electrode as a novel intraneural interface

Peripheral neural interfaces facilitate bidirectional communication between the nervous system and external devices, enabling precise control for prosthetic limbs, sensory feedback systems, and therapeutic interventions in the field of Bioelectronic Medicine. Intraneural interfaces hold great promise since they ensure high selectivity in communicating only with the desired nerve fascicles. Despite significant advancements, challenges such as chronic immune response, signal degradation over time, and lack of long-term biocompatibility remain critical considerations in the development of such devices. Here we report on the development and benchtop characterization of a novel design of an intraneural interface based on carbon fiber bundles. Carbon fibers possess low impedance, enabling enhanced signal detection and stimulation efficacy compared to traditional metal electrodes. We provided a 3D-stabilizing structure for the carbon fiber bundles made of PEDOT:PSS hydrogel, to enhance the biocompatibility between the carbon fibers and the nervous tissue. We further coated the overall bundles with a thin layer of elastomeric material to provide electrical insulation. Taken together, our results demonstrated that our electrode possesses adequate structural and electrochemical properties to ensure proper stimulation and recording of peripheral nerve fibers and a biocompatible interface with the nervous tissue.

Recent progress on smart lower prosthetic limbs: a comprehensive review on using EEG and fNIRS devices in rehabilitation.

The global rise in lower limb amputation cases necessitates advancements in prosthetic limb technology to enhance the quality of life for affected patients. This review paper explores recent advancements in the integration of EEG and fNIRS modalities for smart lower prosthetic limbs for rehabilitation applications. The paper synthesizes current research progress, focusing on the synergy between brain-computer interfaces and neuroimaging technologies to enhance the functionality and user experience of lower limb prosthetics. The review discusses the potential of EEG and fNIRS in decoding neural signals, enabling more intuitive and responsive control of prosthetic devices. Additionally, the paper highlights the challenges, innovations, and prospects associated with the incorporation of these neurotechnologies in the field of rehabilitation. The insights provided in this review contribute to a deeper understanding of the evolving landscape of smart lower prosthetic limbs and pave the way for more effective and user-friendly solutions in the realm of neurorehabilitation.

A dataset of optical camera and IMU sensor derived kinematics of thirty transtibial prosthesis wearers

Motion analysis has played a crucial role in providing gait analysis for prosthetic users. Understanding kinematics in motion analysis allows for the evaluation of the effects of prostheses and the development of a prosthetic component design that aids in walking within the community. However, there are currently limited open datasets available to study the locomotion of individuals using transtibial prostheses, and most research studies involve a limited number of participants. This dataset shows 30 transtibial prosthesis users walking comfortably on a 10-meter walkway inside a laboratory. We offer a set of joint ankles obtained from the inertial measurement unit (IMU) signals in CSV file format. We also provide the optical motion capture (OMC) system’s raw trajectory marker data in C3D file format and joint angle in CSV file format. This open dataset will provide resources for professionals interested in amputee gait for research in amputee gait detection and tracking algorithms. Moreover, the data will be the control data for comparison in developing advanced prosthetic components.

Enhanced orthopedic implant design for transfemoral amputation incorporating a honeycomb structure technology

After lower limb amputation, the primary challenge is to facilitate the patient’s adoption of a prosthetic limb seamlessly, without encountering complications or discomfort. Elevated stress levels within the residual limb, experienced when wearing the socket and while standing or walking, contribute to patient discomfort. As an initial step in this study, we developed a finite element model of above-knee amputation. Additionally, we designed a prototype orthopedic implant composed of several parts, with the lower section featuring a honeycomb structure aimed at absorbing and diminishing stresses at the interface of the residual limb and prosthetic. In this study, finite element models with and without orthopedic implants were analyzed to assess the feasibility and impact of incorporating a honeycomb structure within the implants on stress distribution, particularly at the stump-prosthetic interface. Models with honeycomb-structured implants, at varying densities, showed a reduction in interface stress to approximately 2.15e-2 MPa and 2.01e-2 MPa, compared to 4.5e-2 MPa in model without honeycomb structure in the implant and 7.97e-2 MPa in models without any implants.

Design and Implementation of an Upper Limb Prosthetic Hand Using a Pressure Sensor

Design and Implementation of an Upper Limb Prosthetic Hand Using a Pressure Sensor

A compact solution for vibrotactile proprioceptive feedback of wrist rotation and hand aperture

BackgroundClosing the control loop between users and their prostheses by providing artificial sensory feedback is a fundamental step toward the full restoration of lost sensory-motor functions.MethodsWe propose a novel approach to provide artificial proprioceptive feedback about two degrees of freedom using a single array of 8 vibration motors (compact solution). The performance afforded by the novel method during an online closed-loop control task was compared to that achieved using the conventional approach, in which the same information was conveyed using two arrays of 8 and 4 vibromotors (one array per degree of freedom), respectively. The new method employed Gaussian interpolation to modulate the intensity profile across a single array of vibration motors (compact feedback) to convey wrist rotation and hand aperture by adjusting the mean and standard deviation of the Gaussian, respectively. Ten able-bodied participants and four transradial amputees performed a target achievement control test by utilizing pattern recognition with compact and conventional vibrotactile feedback to control the Hannes prosthetic hand (test conditions). A second group of ten able-bodied participants performed the same experiment in control conditions with visual and auditory feedback as well as no-feedback.ResultsConventional and compact approaches resulted in similar positioning accuracy, time and path efficiency, and total trial time. The comparison with control condition revealed that vibrational feedback was intuitive and useful, but also underlined the power of incidental feedback sources. Notably, amputee participants achieved similar performance to that of able-bodied participants.ConclusionsThe study therefore shows that the novel feedback strategy conveys useful information about prosthesis movements while reducing the number of motors without compromising performance. This is an important step toward the full integration of such an interface into a prosthesis socket for clinical use.

Implementing social and affective touch to enhance user experience in human-robot interaction.

In this paper, we discuss the potential contribution of affective touch to the user experience and robot performance in human-robot interaction, with an in-depth look into upper-limb prosthesis use as a well-suited example. Research on providing haptic feedback in human-robot interaction has worked to relay discriminative information during functional activities of daily living, like grasping a cup of tea. However, this approach neglects to recognize the affective information our bodies give and receive during social activities of daily living, like shaking hands. The discussion covers the emotional dimensions of affective touch and its role in conveying distinct emotions. In this work, we provide a human needs-centered approach to human-robot interaction design and argue for an equal emphasis to be placed on providing affective haptic feedback channels to meet the social tactile needs and interactions of human agents. We suggest incorporating affective touch to enhance user experience when interacting with and through semi-autonomous systems such as prosthetic limbs, particularly in fostering trust. Real-time analysis of trust as a dynamic phenomenon can pave the way towards adaptive shared autonomy strategies and consequently enhance the acceptance of prosthetic limbs. Here we highlight certain feasibility considerations, emphasizing practical designs and multi-sensory approaches for the effective implementation of affective touch interfaces.

PERBEDAAN KECEPATAN BERJALAN PADA PENGGUNA TRANSTIBIAL PROSTHESIS TIPE SACH FOOT DAN SINGLE AXIS FOOT

Background: Amputation can be defined as the act of separating part of the body, part or all of an extremity. Currently, lower limb amputations account for 85-90% of all amputations and transtibial amputation is the most frequently performed type of amputation surgery. One of the problems with transtibial amputation is hyperextension and weakness of the ligaments in the knee. Knee hyperextension is a condition that occurs when the knee joint is extended (straightening the knee) excessively, thus putting pressure on the structure of the knee and the back of the knee joint. Ligament weakness in the knee is weakness in the anterior cruciate ligament, posterior cruciate ligament, medial collateral ligament and lateral collateral ligament. Choosing the right prosthesis components can overcome this. One component that plays an important role is the foot component. Methods: This type of research is observational analytic with a cross-sectional design. The research subjects were 17 transtibial prosthesis users. Data analysis in this study used Spearman Rank Test. Results: Based on the Spearman Rank results, the significance result was 0.653 for the type of foot with hyperextension, while for the type of foot with ligament weakness, the significance result was 0.434. Both variables had variable values > 0.05, meaning there was no correlation between foot type and hyperextension and ligament weakness in transtibial prosthesis users. Conclusion: There is no correlation type of foot to hyperextension and ligament weakness. In future research, it is hoped that research can be carried out with a larger number of samples and a more varied type of foot.

The relationship of hip strength to walking and balance performance in unilateral lower limb prosthesis users differs by amputation level.

Safe and efficient locomotion is a frequently stated goal of lower limb prosthesis users, for which hip strength may play a central yet poorly understood role. Additional research to identify associations between hip strength, balance, and mobility among transtibial and transfemoral prosthesis users is required. To test whether residual and/or intact limb isometric hip strength was associated with lower limb prosthesis users' walking speed, endurance, and balance. Cross-sectional study. Research laboratory. Convivence sample of 14 transtibial and 14 transfemoral prosthesis users. Multiple linear regression was used to evaluate the relationship between isometric measures of residual and intact limb hip strength and walking and balance performance. Measures of isometric hip muscle strength, including peak torque, average torque, torque impulse, and torque steadiness (i.e. consistency with which an isometric torque can be sustained) were derived from maximum voluntary hip flexion, extension, abduction and adduction torque signals collected with a motor-driven dynamometer. Walking speed, endurance, and balance were assessed by administering the 10-meter walk test, 2-minute walk test, Four Square Step Test, and Narrowing Beam Walking Test, respectively. Residual limb hip extensor max torque and abductor torque steadiness explained between 51% and 69% of the variance in transtibial prosthesis users' walking speed, endurance, and balance. In contrast, intact limb hip abductor torque impulse explained between 33% and 48% of the variance in transfemoral prosthesis users' walking speed, endurance, and balance. Our results suggest that unilateral transtibial and transfemoral prosthesis users' walking and balance performance may depend on different hip muscles, and different facets of hip strength. Amputation level-specific hip strength interventions may therefore be required to improve walking and balance performance in unilateral transtibial and transfemoral prosthesis users. The "intact leg strategy" adopted by transfemoral prosthesis users may be due to a variety of prosthesis and biomechanical factors that limit the efficiency with which transfemoral prosthesis users can exploit the strength of their residual limb hip muscles while walking.

Celebrating St Melor at Amesbury Priory

ABSTRACT This article examines relevant information from Amesbury Priory to elucidate the ways in which the priory celebrated the life of their patron saint Melor in a commemorative office. Based on Cambridge, Cambridge University Library Ee.6.16, the article examines ways in which the Amesbury telling of Melor’s life differs from both other English as well as French sources. Drawing upon English breviaries that include lessons for Melor’s feast day, it shows the ways in which they differ from the Amesbury material. Rather than focusing on Melor’s wounding and prosthetic hand and foot, the Amesbury commemorative office emphasises the role of the one female character in the story in the days leading to Melor’s death. The article includes a transcription the breviary sources, and the commemorative office in CUL Ee.6.16 as well as material from two fragmentary breviaries associated with the priory.

Smart ArM: a customizable and versatile robotic arm prosthesis platform for Cybathlon and research

BackgroundIn the last decade, notable progress in mechatronics paved the way for a new generation of arm prostheses, expanding motor capabilities thanks to their multiple active joints. Yet, the design of control schemes for these advanced devices still poses a challenge, especially with the limited availability of command signals for higher levels of arm impairment. When addressing this challenge, current commercial devices lack versatility and customizing options to be employed as test-beds for developing novel control schemes. As a consequence, researchers resort to using lab-specific experimental apparatuses on which to deploy their innovations, such as virtual reality setups or mock prosthetic devices worn by unimpaired participants.MethodsTo meet this need for a test-bed, we developed the Smart Arm platform, a human-like, multi-articulated robotic arm that can be worn as a trans-humeral arm prosthesis. The design process followed three principles: provide a reprogrammable embedded system allowing in-depth customization of control schemes, favor easy-to-buy parts rather than custom-made components, and guarantee compatibility with industrial standards in prosthetics.ResultsThe Smart ArM platform includes motorized elbow and wrist joints while being compatible with commercial prosthetic hands. Its software and electronic architecture can be easily adapted to build devices with a wide variety of sensors and actuators. This platform was employed in several experiments studying arm prosthesis control and sensory feedback. We also report our participation in Cybathlon, where our pilot with forearm agenesia successfully drives the Smart Arm prosthesis to perform activities of daily living requiring both strength and dexterity.ConclusionThese application scenarios illustrate the versatility and adaptability of the proposed platform, for research purposes as well as outside the lab. The Smart Arm platform offers a test-bed for experimenting with prosthetic control laws and command signals, suitable for running tests in lifelike settings where impaired participants wear it as a prosthetic device. In this way, we aim at bridging a critical gap in the field of upper limb prosthetics: the need for realistic, ecological test conditions to assess the actual benefit of a technological innovation for the end-users.

Fiber Bragg grating-based touch-slip sensor for surface roughness detection

To enable humanoid prosthetic hands to accurately identify and grasp objects, a touch-slip sensor based on fiber Bragg grating (FBG) was proposed in this paper. The sensor was designed with a double-layer sensing structure to detect three-dimensional force, sliding information, surface roughness, and compensate for ambient temperature using a reference grating. To analyze the relationship between the sensor surface structure parameters and FBG's vibration signal, the contact sliding model was introduced. By using a finite element simulation, the contact sliding model was validated, and the surface structure parameters of the sensor were determined. A series of experiments were conducted on the sensor’s three-dimensional force detection, temperature calibration, sliding measurement, and surface roughness detection. Using machine learning methods, a regression prediction model was created. The sensor could detect the surface roughness on the sample plate surface more accurately with a maximum error of 8.58×10−4. This sensor has the following advantages: a simple structure, low cost, high linearity, and quick response time. It provides a new design solution for the detection of touch-slips on humanoid prosthetic hands.

The Impact of Sociodemographic Variables on Functional Recovery following Lower Extremity Amputation

ObjectiveWe hypothesize that sociodemographic variables, particularly disadvantaged financial environments, impact both rate of prosthetic utilization and the achievement of ambulation post major amputation. MethodsAll cases in the Vascular Quality Initiative (VQI) amputation module were queried between April 2013 and January 2024. Inclusion was limited to patients who underwent below knee, through knee, and above knee amputation. Two primary outcomes were investigated : Non-ambulatory status after amputation (minimum of 120 days follow up); and, not having obtained a prosthetic limb (minimum of 90 days follow up). The ambulation status and prosthetic status analyses had 6984 and 6793 patients meet inclusion respectively. Multivariable binary logistic regression analysis was performed utilizing variables which achieved univariable significance (P<.05) for the outcomes. ResultsMean follow up for those meeting inclusion was 432 days. Amongst all patients meeting inclusion, 46.7% of patients did not acquire a prosthetic limb and 44.1% were non-ambulatory. Sociodemographic factors with significant multivariable association for the outcome of no prosthetic limb acquisition in follow up were : advancing age (aOR 1.011/year (1.006-1.016), P<.001); female sex (aOR 1.43 (1.28-1.61), P<.001); top 20% ADI representing highest deprivation (aOR 1.24 (1.09-1.41) P=.001); race (P=.002) Insurance status (P=.028) with protective status for commercial insurance (39% rate of no prosthetic) and non US insurance (33%) versus Medicare (51%), Medicaid (48%), VA insurance (49%), Self Pay (42%) and Medicare Advantage (51%). There were numerous co-morbidities which also had association with lack of prosthetic limb acquisition.Sociodemographic variables which achieved multivariable significance (P<.05) for the outcome of non-ambulatory status after major amputation were : female sex (aOR 1.37 (1.23-1.54), P<.001); Medicare insurance (P=.016); advancing age (aOR 1.009/year (1.004-1.014), P<.001); CHF (aOR 1.15 (1.02-1.31), P=.028); and, not living at home in follow up (aOR (3.53 (2.99-4.17) P<.001). Physical therapy at any point after surgery (aOR .742 (.662-.832), P<.001) and commercial insurance (aOR .839 (.737-.956), P=.008) were protective. There were numerous co-morbidities which also had association with non-ambulatory status in follow up. ConclusionsLiving within the most financially disadvantaged areas and race both have a significant independent association with lack of prosthetic limb acquisition following major amputation. Black, Native American and Pacific Islander demographic patients experience lack of acquisition at a higher rate than White and Asian patients independent of co-morbidities and socioeconomic co-variables. Female patients obtain a prosthetic limb and ambulate less frequently than males after major amputation, largely due to a higher rate of above knee amputation. Co-morbidities, and not socioeconomic variables are the leading drivers of non-ambulation.

Revolutionizing Human Augmentation: The Future of Neuroprosthetics and Brain-Computer Interface Technologies

The future of neuroprosthesis and brain-computer interface (BCI) technologies is poised to transform medical treatments, cognitive development, and human-machine interaction. Neuroprosthetics, which integrate artificial devices with the nervous system to restore or enhance sensory and motor functions, have already improved the lives of people with disabilities. Advances in materials science and neural interfacing are taking these technologies even further, enabling more seamless integration and better control of prosthetic limbs and sensory devices. As these technologies improve, they may soon be able to restore complex functions such as speech, vision, and memory. At the same time, BCIs go beyond traditional applications for neurological disorders, opening up possibilities for cognitive enhancement, neural data transfer, and immersive virtual experiences. With advances in machine learning and neuroimaging, BCIs can enhance cognitive abilities, treat neurological diseases, and redefine human-computer interaction. However, these technologies also raise ethical, social, and security concerns. The risk of misuse, such as unauthorized access to neural data, and the potential creation of cognitive hierarchies emphasize the need for robust regulation. Ensuring accessibility and equity is also essential to ensure that the benefits of these advances are shared equitably. The development of neuroprostheses and BCIs has had a positive impact.

Silicon-Based Piezoresistive Stress Sensor Arrays for Use in Flexible Tactile Skin.

Bioinspired robotics and smart prostheses have many applications in the healthcare sector. Patients can use them for rehabilitation or day-to-day assistance, allowing them to regain some agency over their movements. The most common way to make these smart artificial limbs is by adding a "human-like" electronic skin to detect force and emulate touch detection. This paper presents a fully integrated CMOS-based stress sensor design with a high dynamic range (100 kPa to 100 MPa) supported by an adaptive gain-controlled chopping amplifier. The sensor chip includes four identical sensing structures capable of measuring the chip's local stress gradient and complete readout circuitry supporting data transfer via I2C protocol. The sensor takes 10.2 ms to measure through all four structures and goes into a low-power mode when not in use. The designed chip consumes a total current of ∼300 μA for one complete operation cycle and ∼30 μA during low power mode in simulations. Moreover, the complete design is CMOS-based, making it easier for large-scale commercial fabrication and more affordable for patients in the long run. This paper further proposes the concept of a tactile smart skin by integrating a network of sensor chips with flexible polymers.

Virtual Assessment of Functional Mobility in Lower Extremity Prosthesis Clients: An Exploratory Study

ObjectiveTo investigate the relationship between patient perception of lower extremity function and a home-based virtual clinician assessment of mobility in lower limb prosthesis clients. DesignDescriptive observational study using a clinician-administered functional mobility survey and timed Up and Go test to assess lower extremity function under supervision. SettingHealth Insurance Portability and Accountability Act-compliant online virtual platform. ParticipantsTwelve lower limb loss clients currently using prostheses, aged ≥19 years, not pregnant, and with no stroke, seizure disorder, or cancer. InterventionsNot applicable. Main Outcome MeasuresMain outcomes were mobility survey scores and mean timed Up and Go duration. ResultsMost participants reported significant ease of completing basic indoor ambulation and toileting tasks (66%-75%) and significant difficulty in running or prolonged ambulation activities (83%) requiring use of lower limb prosthesis. Timed Up and Go test was faster (11.0±2.9 s) than the reference range for transtibial prosthesis users and negatively associated with self-reported lower extremity functional status (r=−.70, P=.02). ConclusionsSelf-reported movement with lower limb prostheses at home and evaluation of mobility via a virtual platform is a feasible assessment modality that may reduce the frequency of therapy visits, defray some rehabilitation costs, and minimize the travel burden to distant prosthetic clinics.

Thermoregulatory integration in hand prostheses and humanoid robots through blood vessel simulation

In this paper, we introduce an innovative approach for generating robotic faces with a thermal signature similar to that of humans and equipping prosthetic or robotic hands with a lifelike temperature distribution. This approach enhances their detection via infrared cameras and promotes more natural interactions between humans and robots. This method integrates a temperature regulation system into artificial skin, drawing inspiration from the human body’s natural temperature control via blood flow. Central to this technique is a fiber network simulating blood vessels within the artificial skin. Water flows through these fibers under specific temperature and flow conditions, forming a controlled heat release system. The heat emission can be adjusted by changing the dilation of these fibers, primarily by modulating the frequency of circulation. Our findings indicate that this approach can replicate the varied thermal characteristics of different human faces and hand areas. Consequently, the robotic faces appear more human-like in infrared images, aiding their identification by infrared cameras. At the same time, the prosthetic hands achieve a more natural temperature, reducing the discomfort typically felt in direct contact with synthetic limbs. The aim of this study was to address the challenges faced by the users of prosthetic hands. The results from this study show a promising direction in humanoid robotics, fostering improved tactile interactions and redefining human–robot relationships. This innovative technique facilitates further advancements, blurring the lines between artificial aids and natural biological systems.