A study on Cost Effective Lower Limb Orthotics with 3d Printing and Composite Material

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A study on Cost Effective Lower Limb Orthotics with 3d Printing and Composite Material Dr. M Arul Prakash1, Kawin Harshan SU2, Gnamath Basha A3 1Asso. Prof, Dept. Of Mechanical Engineering, Sri Sairam Engineering College, Tamil Nadu, India 2,3Student, Dept. Of Mechanical Engineering, Sri Sairam Engineering College, Tamil Nadu, India ---------------------------------------------------------------------***--------------------------------------------------------------------prosthetics and orthotics, these actuators are essential for Abstract - This paper examines the application of 3D

printing and composite materials in the production of lower limb orthotics, focusing on achieving both customization and cost-effectiveness. By harnessing the flexibility of 3D printing and the durability of lightweight materials, orthotic devices are tailored to meet individual anatomical needs, improving patient comfort and mobility.

These technologies reduce manufacturing time, minimize material waste, and lower production costs. The study also identifies current limitations and explores future improvements, such as the integration of advanced medical imaging for even more precise designs, aimed at enhancing both patient outcomes and production efficiency.

ensuring user safety and comfort. Elastic actuators are preferred in dynamic applications over rigid ones, but current compliant cobots are often too costly or complex for widespread use in these fields. This study introduces a low-cost, sensorized elastic actuator designed for prosthetic and orthotic applications. The modular design, made possible with 3D printing, enables quick customization and cost-effective production. Both the hardware and software are open-source, providing accessible resources for students, researchers, and professionals. Additionally, the system supports impedance and admittance control, further enhancing its adaptability and functionality [1].

Key Words: Custom orthotics, 3D printing, composite

Individuals with neurological impairments, particularly those with cervical spinal cord injuries (SCI), often struggle with daily tasks due to triceps weakness or loss of function. More physically demanding activities, such as sit-skiing, are often impossible due to the strength required. While research into exoskeletons designed to enhance arm extension is ongoing, no commercially available solutions currently exist. Most designs rely on electric motors, which require bulky power sources and wiring, limiting their practicality for everyday use[2].Although passive power systems for upper limb exoskeletons have been explored, none have yet provided adequate strength for tasks like sit-skiing. This research introduces a passively actuated exoskeletal arm brace designed with two adjustable strength modes: one for low-level gravity compensation to assist with range of motion, and another for weight-bearing activities. The result is an affordable, lightweight, modular device, customizable to meet the specific needs of individual users.

materials, lower limb, medical imaging.

1.INTRODUCTION The possible uses of 3D printing and composite materials in producing reasonably priced lower limb orthoses are examined in this work. It investigates the advantages of these technologies that is, more design flexibility, better manufacturing efficiency, and better biomechanical performance. Moreover, the research tackles important obstacles and future prospects in combining these developments for more general clinical and personal uses.

These devices have historically been produced using traditional techniques like metal fabrication and thermoforming plastics, which can be expensive, timeconsuming, and frequently lead to little customisation.

Advances in material science and additive manufacturing have made 3D printing a promising technology for creating highly customisable and reasonably priced orthotic solutions.

This paper introduces a soft wearable orthotic device designed to assist with gait. Constructed primarily from soft materials, the device weighs only 680 g when worn on the lower extremities, minimizing any additional inertia during movement. The device employs fully soft pneumatic artificial muscles (PAMs) as actuators, which operate at low threshold pressures. A group of four PAMs generates force for ankle plantarflexion during specific phases of the gait cycle. Gait detection is

2.COLLABORATIVE ROBOTS AND ACTUATORS FOR ORTHOTIC & PROSTHETIC APPLICATIONS Collaborative robots, or cobots, are increasingly popular due to their ability to safely operate alongside humans in shared environments. A key aspect of their design is the use of compliant actuators, which help prevent damage during accidental collisions. In

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facilitated by two inertial measurement units (IMUs) attached to the calf and foot braces. The orthotic device delivers a force of 65 N for ankle plantarflexion, amounting to 3.5% of the typical biological force exerted at the ankle during walking [3].

presents a novel mechanical design for the lower limb exoskeleton robot. Initially, the anatomical features of the human lower limbs are examined. Building on this analysis, the design includes an exoskeleton thigh with an adjustable dip angle and length. Additionally, an ankle mechanism is introduced that allows for flexion, dorsiflexion, and adduction, enabling users to independently adjust their centre of gravity. Finite element analysis conducted using SolidWorks Simulation demonstrates that the design possesses adequate stability and strength margins for the key components.

3.ROBOTIC REHABILITATION FOR UPPER AND LOWER LIMBS Robot-assisted physical therapy for the upper limb is increasingly popular, especially for the wrist, which is highly complex due to its multiple degrees of freedom.

Over the last three decades, several robotic devices have been created to aid in wrist rehabilitation, offering intensive therapy and repetitive exercises at a reduced cost. These robots also provide performance feedback, making therapy more effective and customized to a patient’s disability level.[4] Current research in wrist rehabilitation robots focuses on two key areas: mechanical design and control strategies. Mechanically, these devices are either end-effector-based or wearable robotic orthoses. In terms of control, they use either convectional trajectory tracking or assist as-needed methods to tailor support for individual needs. This review examines the design and control innovations in wrist rehabilitation robots, evaluates their performance in healthy and neurologically impaired users, and suggests future research directions for enhancing these robotic systems.

Dexterity plays a crucial role in the research and development of rehabilitation robots. This paper focuses on enhancing the design mechanisms and optimizing control by examining the dexterity of the lower limbs, providing valuable insights for rehabilitation robot designs. Building on the anatomical characteristics of human lower limbs, the study expands traditional three-dimensional modelling to a six-dimensional framework using spinor theory.

Furthermore, it establishes a kinetic analysis model to assess the manipulability and dexterity of lower limbs.

The feasibility of these analyses is confirmed [7] through experiments conducted on a powered RGO platform. The findings indicate that analysing and evaluating the dexterity of human lower limbs is highly feasible. The experimental results validate the effectiveness of the new approach for designing rehabilitation devices. Additionally, the identification of optimal motion points (BMPs) during human movement contributes significantly to developing human analysis models and designing effective rehabilitation devices.

This paper introduces a modular, distributed "multirobot" cyber-physical system designed to aid children with developmental delays in learning to walk. The system features two key modules:[5] a tethered cable pelvic module with up to six degrees of freedom (DOF) for modulating pelvic motion in three dimensions, and a two-DOF wearable hip module focused on supporting hip flexion. Both modules are lightweight and minimally restrictive, able to function independently or in tandem, offering adaptable and personalized assistance. The system achieved high-precision motion tracking, with the pelvic module exhibiting a root mean square (RMS) error of approximately 2 mm and the hip module achieving less than 0.1 mm RMS error. Coordinated functionality of both modules was demonstrated on a mannequin with articulated, instrumented lower limbs.

This study describes a powered lower-limb orthosis intended to help people with spinal cord injuries (SCI) achieve a more functional stride. In addition to providing supportive torques at the hip and knee joints, the orthosis is equipped with a control system and user interface that enable upper-body movements to manipulate the powered device. The orthosis and control system were tested on a paraplegic individual (T10 complete) to assess its efficacy. An first evaluation of the device's ability to assist with basic walking was given by the trials. Walking among parallel bars at an average pace of 0.8 km/h was successfully made possible by the orthosis and its control mechanism, as shown by the data and supporting video evidence from these studies [8].

The lower limb exoskeleton robot is designed for rehabilitation training and assists patients with mild conditions or those recovering from rehabilitation.

However, challenges arise from the misalignment between the exoskeleton's mechanical structure and the human body, along with inadequate design elements.

These issues can disrupt the fixed gait during rehabilitation and hinder the patient's ability to adapt to gait information, ultimately decreasing rehabilitation effectiveness.[6] To address these concerns, this paper

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This paper presents a controller designed for a lowerlimb exoskeleton that facilitates variable-geometry stair climbing and descending for individuals with lower limb paralysis. The performance of the controller was assessed using a subject with a T10 complete spinal

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cord injury (SCI) on two different[9] staircases: one featuring a riser height and tread depth of 18.4× 27.9 cm (7.25 × 11 in) and the other measuring 17.8 × 29.8 cm (7 × 11.75 in). The controller successfully enabled both ascent and descent of the stairs without the need for specific adjustments for each staircase. The results indicated an average stepping rate of 12.9 steps per minute during ascent and 14.6 steps per minute during descent.

orthosis. The Jebsen-Taylor Test of Hand Function (JTTHF) was used to assess hand performance, showing improvements in writing (13 seconds), lifting small objects (0.9 seconds), and simulated feeding (69.3 seconds). The customized orthosis not only enhanced functional abilities but also provided a comfortable fit, improved aesthetics, and better overall usability [12].

This paper presents a new method for controlling force in exoskeletons using twin foot force sensors, called proportional force control. To aid in the analysis of the human-machine system, the paper first describes the dual foot force sensor mechanism before presenting a one-dimensional lower limb model that has been simplified. After that, a comparison between the suggested proportional force control method and two traditional control techniques—desired force control and trajectory tracking control—is explored.

Performance is assessed by simulation trials, and results show that the twin foot force sensor force control approach may proportionately increase human strength and give consumers a concrete sense of control and immediate feedback [10].

4.3D PRINTING AND CUSTOMIZATION PROSTHETICS & ORTHOTICS

Fig-4.1 Fabrication Of AFOs By 3D Printer[12].

The development of a novel lower limb prosthesis that can dynamically modify its volume and stiffness in accordance with the demands of the user is covered in this study. The socket's inner side of the prosthesis is equipped with bags containing Magneto-Rheological (MR) fluid, which may be adjusted in size and viscosity to change the socket's properties. Total surface bearing (TSB) sockets have been one of the most often used alternatives over the last 20 years. Because[13] TSB sockets can equally transfer body weight over the full socket surface, users find them to be quite useful.

Nevertheless, a noteworthy constraint is their incapacity to adjust to variations in the user's stump volume.

Results from experiments show that the newly designed MR socket performs better than conventional TSB sockets because it permits real-time adjustments in both size and viscosity, providing enhanced comfort and functionality for the user.

IN

3D-printed prosthetics have made significant strides in lowering the high costs of traditional designs, addressing affordability challenges for amputees.

However, the World Health Organization reports that only 5-15% of those in need have access to proper prosthetic care. To tackle the issues of limited supply and high costs, this paper introduces a self- trainable, user-customizable system for 3D-printed prosthetic hands. The system allows users to create any gesture they need, improving accessibility and functionality. By utilizing a Radial Basis Function (RBF) network with 3channel EMG sensor inputs, the system achieves a 94% success rate in replicating[11] desired gestures. This approach offers a cost- effective solution that enhances the performance of prosthetic hands, tailored to meet individual user needs.

Fourth-degree burn scar contracture severely reduces joint mobility and frequently calls for dynamic orthotic intervention. Orthotic devices that allow for minor angular adjustments—ideally no more than 2°— are the most effective. This work describes a model for an all-inclusive treatment plan and presents a revolutionary design that allows for angle variations of less than 2° over the course of a day. Trigonometric and goniometric calculations were used in the construction of the device, which was made utilising orthotic techniques. A screw-threaded mechanism designed especially for controlled angular extension under 2° is used in this design. This device is especially well-suited

Cerebral Palsy (CP) affects over 100 million children, with more than 60% experiencing significant hand impairments due to involuntary movements and spasticity. Orthoses are commonly used as therapeutic tools to help children with CP improve hand functionality. This research focused on designing, developing, and evaluating a custom wrist-hand orthosis for a child with CP using 3D technologies. The process involved high-precision 3D scanning to capture wristhand anatomy, open-source software for modelling, and a cost-effective 3D printer for manufacturing the

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for clinical use due to its modular design and affordable production costs, guaranteeing accessibility for efficient patient care [14].

while providing additional services that are in line with current rehabilitation procedures [16].

6.ACCESIBILITY, COST-EFFECTIVENESS AND REHABILITATION IN LOW-INCOME REGIONS Due to the lack of access to trauma care and rehabilitation facilities in low-income nations, the socioeconomic effects of limb disability brought on by accidents, trauma, or congenital disorders are especially severe. In these areas, the majority of medical schools do not have a specific curriculum that addresses disability and rehabilitation, and many of them are ill-equipped to give students the professional skills they need. The development and manufacture of medical rehabilitation equipment in conjunction with the education of credentialed rehabilitation specialists is a pragmatic strategy for improving physical rehabilitation services in low-income nations.

Rehabilitation-related technologies, such prosthetics and orthotics, can greatly improve the functional skills of people with limb limitations, especially when paired with appropriate software and hardware solutions.In this work, a lowcost mechatronics proof-of-concept is presented for use by engineers, physical therapists, and students who are involved in the design and manufacture of orthotic and orthotic devices for the upper and lower limbs. The study integrates[17] basic biomechanical principles assessed by means of practical approaches involving prototype building as well as theoretical approaches like the finite element method. The suggested methodology is a useful teaching tool for training in rehabilitation. In addition, the establishment of efficient and long-lasting rehabilitation technologies and services in developing nations depends on the promotion of a collaborative environment among scientists, engineers, and rehabilitation specialists.

Fig-4.2 Various Thickness Of AFOs The Arrow Indicates Increase Thickness[14].

5.AUGMENTED REALITY AND TECHNOLOGIES IN REHABILITATION

DIGITAL

Augmented reality (AR) has advanced recently, greatly improving human-computer interaction and opening up new applications in a variety of sectors. This study presents a system that efficiently records and stores people's body positions by fusing augmented reality (AR) components with motion capture technologies. The system seeks to generate optimal rehabilitation regimens, especially for users with lower limb orthotic or prosthetic devices, by quantifying these captures through virtual tools. The aim of this research is to assess the viability of employing this augmented reality tool in physical rehabilitation environments, ultimately leading to enhanced quality of life for people with impairments.[15] This method improves the entire rehabilitation experience by providing reasonably priced add-on services to the ones that are currently offered.

Augmented reality (AR) has advanced recently, greatly improving human-computer interaction and opening up new applications in a variety of fields. This study provides a system that efficiently records and stores human body positions by combining augmented reality (AR) features with motion capture technology.

The system uses virtual tools to quantify these recorded postures in order to create suitable rehabilitation regimens, especially for people who use lower limb orthotic or prosthetic devices. This study's main goal is to determine whether or if this technology can be used in the field of physical rehabilitation, which will ultimately help people with impairments live better lives. This strategy keeps the framework inexpensive

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Fig-6.1 Main Feature Of Orthosis AFOs[17].

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This assessment looks at a number of areas related to wheelchair (WC) and lower-extremity prosthesis (LEP) technology and service delivery. It demonstrates how recent breakthroughs in LEP technology have emerged in low- income nations through considerable research and fieldwork. In order to increase the manufacturing capacity of LEPs, the article addresses the required technological advancements and related research initiatives. It also examines various approaches to the planning, production, and distribution of wheelchairs in low-income environments. Finally, it provides an overview of previous studies and current efforts to enhance research capacities in this field.

Ultimately, the paper offers a thorough examination of the physical, social, cultural, and economic obstacles that India faces, highlighting the difficulties in successfully putting this technology into practice [18].

transitions, a leave-one-out cross- validation technique was used for both training and validating the SVM classifier. The study also looked at using lag windows to improve detection precision. The suggested approach showed a low frequency of false positives and a high detection rate for posture alterations [20].

8.INTELLIGENT LOWER ROBOTS &EXOSKELETONS

By using materials that closely resemble the mechanical characteristics of the human musculoskeletal system, soft robots can improve performance without obstructing natural movement.

This research offers a bio-inspired soft active orthotic device meant to enhance ankle dorsiflexion during walking. The apparatus uses a Pneumatic Artificial Muscle (PAM) made of silicone that actuates quickly to offer angular support at the ankle joint. The use of this PAM is maximised by its unique pneumatic network construction, which is designed to match the foot-ankle anatomy ergonomically. After preliminary testing to assess the PAM's features, ankle angle data gathered during the gait cycle was used to build a control method.

Next, a pilot study was conducted to evaluate the efficacy of the device. The outcomes[19] show that the dynamic stability of the ankle joint is much improved by this soft active orthotic device. In the end, it could improve walking stability for elderly people who are fragile or at risk of falling. It has potential as a real-time augmentation solution.

Body and machine work together seamlessly thanks to a combination of machine learning, force and position micro- sensors embedded in the fabric layer, and small but strong axial flux motors placed at the body's natural rotational locations. Physical of the design and optimisation of the new lower limb muscle assist robot technology, which is one of the most cutting-edge solutions and the industry's future [22].

This work describes a new method for the early identification of posture transitions in a motorised orthotic brace intended to help older people with sit-tostand transfers. A linear Support Vector Machine (SVM) classifier is used by the detection system; it is trained with features taken from sensor signals that are integrated into the orthosis. These sensors consist of force sensors, gyroscopes, potentiometers, and accelerometers. Nine healthy individuals participated in a range of activities, including standing, walking, and sitting transitions, from which data were collected. To precisely label every posture transition, the sensor data was processed, normalised, and manually annotated. To accurately detect the early start of sit-to-stand

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SUPPORT

This study presents a novel intelligent lower limb muscle support robot intended for daily usage, displaying state-of- the-art design advances that put the needs of the user first and reduce physical strain. The goal of this assistive device's creation is to improve human-computer interaction by utilising cutting-edge technologies. Four main areas are the centre of the design: Firstly, the robot is made up of four parts: a walking boot, a leg brace, a belt, and a mechanical framework. These parts are designed to look more like athletic gear than typical wearable robotics. Second, it mimics the muscles, tissues, and bones of the human body by combining soft and hard materials, taking inspiration from human anatomy. Soft, flexible materials, such as neoprene, are used to create the innermost layer, which feels comfortable[21] on the skin. Third, the outer layers get stiffer and stiffer with time, using carbon fibre to reduce weight and boost strength. Last but not least, the robot has sensors that dynamically track human movements, enabling realtime modifications as well as focused help and force enhancement. Through a specialised app, users may obtain data and positional information, improving the device's overall usability and performance.

7.SPECIALIZED ORTHOTIC SOLUTIONS FOR MOBILITY ASSISTANCE

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LIMB

A lower limb exoskeleton intended to aid gait in people with neuromuscular impairments is presented in this research. The authors stress two crucial elements to guarantee efficient functioning. For the exoskeleton to calculate the right amount of help required during different walking phases, it must first have trustworthy real-time gait phase detection capabilities. Second, when the user needs little assistance, the device should not interfere with their natural gait dynamics. To do this, the exoskeleton needs to be able to reduce its passive dynamics, which include[23] friction, inertial, and gravitational forces that can obstruct movement. In order to improve user experience and mobility, the design

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strives for active compensation of these passive dynamics. The creation and application of these two fundamental components—real-time gait phase detection and the passive dynamics are actively cancelled within a prototype exoskeleton. The usefulness of these characteristics is confirmed by experimental results, which also show how they could help users with gait support. By taking this novel method, the team hopes to further the development of assistive technology that improve mobility for those with lower limb disabilities.

from a clinical trial involving three paralyzed patients indicate that knee power is comparable to that of healthy individuals, with peak values reaching up to 5.9 W/kg.

Peak knee joint torque was measured at 1.8 Nm/kg.

Significant variations were observed between patients, based on their specific conditions. Additionally, all systems experienced impacts with accelerations exceeding 85 m/s² in extreme situations. These findings highlight the importance of mechanical durability in designing supportive systems, as patient pathology plays a major role in the stress experienced by the device [26].

Lower limb paralysis significantly reduces mobility for affected individuals. Computer-controlled leg brace systems offer new possibilities by enhancing mobility safety, particularly on uneven terrain, inclines, steps, and stairs. This article presents such a system, where the knee joint of the brace was equipped to record sensor data over several weeks of home use, capturing highresolution motion information. A clinical trial with 8 patients, each with varying conditions, revealed that the system was used for an average of over 10 hours per day, with patients taking more than 2,100 steps [24].

This paper presents a model for a lower-limb exoskeleton robot featuring three degrees of freedom and automatic alignment with the knee joint. The model focuses on enhancing the adaptability of the exoskeleton to various motion postures and human body structures.

A sensor mechanism is integrated into the second joint of the exoskeleton to ensure proper coordination between the robotic joint and the human knee. The design process involved modelling the exoskeleton using SolidWorks, followed by simulations and analyses conducted in MATLAB to assess the model's feasibility.

The findings indicate that the developed lower-limb exoskeleton robot demonstrates[27] high safety standards while enhancing the coordination between the user's legs and the robot. This research contributes to the creation of a well-structured and user-friendly lower-limb exoskeleton rehabilitation device, aligning the knee joint of the lower extremity with the robotic joint, thereby improving user acceptance and safety.

This paper details a powered lower-limb orthosis designed to assist individuals with spinal cord injuries (SCI) by providing supportive torque to both the hip and knee joints. Weighing 12 kg, the orthosis can deliver up to 40 Nm of torque with a hip range of motion between 105° flexion and 30° extension, and knee movement between 105° flexion and 10° hyperextension.

Controlled by a custom embedded system, the device is powered by a lithium polymer battery that supports one hour of continuous walking. To assess its effectiveness, the orthosis was tested on a paraplegic subject with a T10 spinal injury. Data from the trial revealed consistent hip and knee movements with an average walking speed of 0.8 km/h. The power consumption per hip and knee joint was around 25 W and 27 W, respectively, resulting in a total power usage of 117 W during walking.[25] A video demonstrating the subject's walking performance is available in the supplemental material.

This paper introduces an innovative test system designed to simulate the human lower limb, offering a reliable alternative for experiments assessing the performance of lower limb exoskeletons, particularly those that counteract gravity. Utilizing a wire-driven mechanism, the system can replicate the rotational movements of the hip and knee joints, effectively mimicking human gait. This approach provides safer and more dependable testing conditions compared to traditional methods involving human participants. By using this simulation test system, researchers can evaluate the efficiency of energy consumption in exoskeletons. A prototype of the human lower limb simulation test system has been designed and built, and experimental results confirm the effectiveness of the proposed method. The findings indicate significant potential for diverse testing applications in the field of exoskeleton technology [28].

Exoskeletal systems are becoming increasingly vital for the rehabilitation of individuals with lower limb paralysis. While these systems are primarily used in clinical settings, devices designed to assist with daily activities are now emerging.

However, the unpredictability of home environments introduces new challenges and unknown loading conditions. This paper presents a novel orthotic system developed to support people with lower limb paralysis in their everyday routines. To better understand the mechanical stresses on the device, sensors were added to the knee joint unit to measure motion, forces, and power during real-world use. The impact of users' remaining functional abilities on these measurements was also explored. Initial results

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Although significant obstacles remain in the mechanical design of lower limb exoskeletons, developing effective control strategies is equally crucial.

Given that exoskeletons operate as highly coupled human-robot systems characterized by complex

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dynamic models and diverse working environments, it is essential for the control mechanisms to align with user intentions without depending on inaccurate models.

This paper introduces a motion control strategy for a lower limb exoskeleton focused on providing efficient and flexible assistance during collaborative squatting.

The control framework is tailored for an exoskeleton equipped with a force sensor positioned on the back. It employs a high-level force-velocity admittance model to interpret human intentions based on interaction forces, complemented by a low-level PD (ProportionalDerivative) closed-loop velocity control that incorporates gravity compensation. Experimental results demonstrate the feasibility and effectiveness of this proposed control strategy when implemented with the exoskeleton [29].

walking, stair climbing, stair descending, ramp ascending, and ramp descending. Data was collected using mechanical sensors integrated into powered prostheses, focusing on steady-state and transitional movements performed by six transfemoral amputees across the five locomotion modes. Initially, the intent recognition system achieved an accuracy of 84.5% with steady-state training data alone. However, by including data from seamless transitions, the accuracy improved significantly to 93.9%. Furthermore, training with a single analysis window during critical moments, such as heel contact and toe-off, proved to be more effective than using multiple analysis windows.[32] Overall, this research highlights the effectiveness of an intent recognition system in facilitating automatic and fluid transitions between various locomotion modes for transfemoral amputees utilizing powered prosthetic limbs.

To enhance the safety and efficacy of lower limb exoskeleton robots (LLER) during rehabilitation training, this paper introduces a novel control strategy grounded in human plantar reaction forces. Initially, plantar reaction force and gait data are gathered from a healthy individual using a 3D experimental platform, along with the calculation of joint torque and gait trajectory through dynamic and kinematic analyses. The derived gait trajectory serves as the target trajectory, while the corresponding joint torque is applied to the LLER, enabling it to mimic[30] and follow the desired movement. Subsequently, a radial basis function neural network controller is designed to adjust for input torque based on tracking errors. The simulation results demonstrate the effectiveness of this proposed approach in improving rehabilitation outcomes for patients with lower limb paralysis.

A prosthesis is a mechanical device designed by experts to assist individuals who have undergone amputation, facilitated not only their daily activities but also minimized the energy expenditure required for these tasks. Given the significant number of amputees globally, it is crucial to create prosthetic devices that cater to their specific needs.

The energy expenditure of lower limb amputees can be measured using indirect calorimetry, which assesses oxygen consumption during activities like walking or climbing stairs. This paper provides a review of the various types of prostheses developed to date and examines their impact on the energy cost for lower limb amputees [33].

10.3D PRINTING IN ORTHOTICS & ASSISTIVE TECHNOLOGY

9.PROSTHETICS AND ADAPTIVE INTERFACES

Adding high-performance inorganic fillers to 3D printing resin can significantly enhance its mechanical properties and thermal conductivity. However, these fillers also affect the 3D printing process[34] itself. This paper presents the development of a high-performance 3D printing composite resin, focusing on the impact of boron nitride micron sheets (hBN) on the resin's viscosity and light transmittance. The study explored suitable process parameters for optimal 3D printing.

Results showed that with 30 wt% hBN, the resin's viscosity increased to 2426 mPa.s, remaining within the acceptable range for photocurable 3D printing (below 3000 mPa.s). Although hBN accelerated the resin's curing rate, it also hindered UV light transmission, reducing the curing thickness of the composite resin with 30 wt% hBN to 1.2 mm—131% thinner than the pure resin. These findings provide valuable insights for developing sustainable 3D printing composite resins.

Lower limb amputees frequently experience skin injuries due to mechanical forces, particularly shear stress, while using prosthetic devices. To address this issue, this paper introduces a new type of adaptive prosthetic and orthotic interface that incorporates a capacitive shear stress sensor.[31] The design and transfer function of the sensor are explained, and preliminary tests are provided to demonstrate its functionality in mitigating shear-related skin injuries.

Recent advancements in lower-limb prosthetics have led to devices that can actuate both knee and ankle joints, allowing amputees to engage in complex activities such as climbing stairs and traversing sloped surfaces. Despite these capabilities, the transitions between different locomotion modes and standard walking remain non-automatic and disjointed. This study outlines the development and training of a highlevel intent recognition system designed for lower- limb prosthetics, enabling smoother transitions between

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This study introduces a method for producing magnetic composites tailored for 3D printing using stereolithography (SLA). The method is applied to the

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3D printing of soft- magnetic composite materials, specifically for creating toroidal magnetic core samples.

The production sequence for these 3D-printed samples using SLA technology is outlined, followed by the fabrication of test samples. The magnetic properties of the samples, including magnetic permeability and the magnetization curve, are measured to assess nonlinearity. The proposed approach enables the rapid creation of complex magnetic cores through SLA, allowing precise control of magnetic properties in three dimensions [35].

Material Properties

Tensile

Polypropylene ABS M30 AFO Material Material (FDM 3D (Conventional Printer) Method)

This review examines the use of biochar as an additive in 3D printing materials, focusing on its ability to enhance mechanical and thermochemical properties.

Biochar, derived from the thermochemical processing of biomass, offers high porosity, a large specific surface area, and carbon-rich composition, making it an excellent component for sustainable manufacturing. The review explores the application of biochar composites in various 3D printing materials, such as polymers, metals, ceramics, and fibres, highlighting improvements in strength, durability, and performance. Additionally, biochar's contribution[38] to environmental sustainability is emphasized. Challenges related to achieving uniform dispersion of biochar and the need for advanced printing technologies are also discussed.

Overall, biochar integration presents a promising opportunity to advance additive manufacturing while maintaining ecological and functional standards.

Nylon Polyamide (SLS 3D Printer)

4650 MPa

9244 MPa

Strength

4500-6000 MPa

Tensile

1724 MPa

2060 MPa

2100 MPa

7-13

41.6

82.8

11.

BIOMECHANICS MONITORING

Modulus Elongation %

80-102

75-115

93-122

Hardness TABLE I. Mechanical

properties comparison chart of different 3D printing machines[35].

This work presents magnetic hysteresis models for composite materials created through Fused Deposition Modeling (FDM) 3D printing. The composite consists of a polymer matrix embedded with microscale iron powder, with samples produced by varying the iron content and microfill patterns. The magnetization of these samples was tested, and single-frequency hysteresis loops were obtained. The data from these measurements were used to fit parameters for the JilesAtherton and Stoner-Wohlfarth hysteresis models.

These findings offer valuable insights for further modelling applications and help optimize the predictive control of magnetic properties in 3D-printed polymer composites [36].

This study examines UV-curable polymer composites to evaluate their suitability for creating dielectrics with functionally graded materials (d-FGM) using stereolithographic 3D printing. Several dielectric properties, including permittivity, dielectric loss, and breakdown strength, are analysed on the fabricated test samples. Additionally, the 3D printability of the polymer composites is assessed by measuring their viscosity[37] and curing depth. The impact of ceramic filler type, volume fraction, and particle morphology on both dielectric performance and 3D printing viability is also discussed in detail.

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REHABILITATION

This research examines the kinematic angles of the lower limbs during the execution of jumping jacks, a common exercise performed by many individuals. The success of this exercise relies on maintaining appropriate kinematic alignment of the lower limbs, which is vital for effective execution. By analysing variations in lower limb movement throughout multiple repetitions, individuals can enhance their exercise technique. During the study, a participant performed jumping jacks for five minutes, and motion capture technology was utilized to assess differences in posture at both the beginning and end of the exercise session. Further angle analysis was conducted using MATLAB software. An Artificial Neural Network (ANN) model was also created to forecast the angles of the lower limbs, taking into account inputs such as muscle activation signals[39] derived from electromyography (EMG) and the angular acceleration of the limbs. The results indicated that the ANN model effectively predicted lower limb kinematics. This study emphasizes that by examining muscle activation and angular acceleration, the ANN model can provide insights into the effectiveness of the jumping jack exercise.

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different designs of artificial feet, knee and ankle joints, as well as both transfemoral and transtibial prosthetic devices. When configuring and testing control systems for active and semi-active prostheses, the simulator operates as a model of a human-machine system, where the gait simulator represents the “human” element and the prosthesis serves as the “machine.” A key advantage of this test bench is its capability to evaluate lower limb prostheses and their components for static and cyclic strength, adhering to the ISO 2006:10328 standards [41].

Fig-11.1 Loading Test For AFOs[39].

This study emphasizes the significance of monitoring knee joint angles during lower-limb activities, particularly for patients with knee disorders undergoing rehabilitation. Traditional methods, such as inertial measurement units (IMUs) and motion capture systems, often face challenges like drift and high costs. In response, we have developed a wearable kneepad sensor utilizing textile-based resistive strain sensors to effectively measure knee angles during motion. These sensors detect changes in resistance due to deformation as the knee bends. To enhance accuracy, we integrated an encoder with the kneepad sensor mounted on a prosthetic limb and used a linear mapping method to calibrate the sensor data against the encoder's measurements. The calibrated sensor achieved an R² value of 0.956, with a mean absolute error of 6.15° and a mean squared error of 64.35 in measuring knee angles.

The results demonstrated the sensor's ability to accurately capture knee angles during two lower- limb movements: sit-to-stand (STS) transitions and knee extensions. This comfortable, wearable kneepad sensor shows promise in detecting knee angles across various environments, offering potential applications in healthcare and robotics [40].

Fig-12.1 Testing setup of AFOs [41]

13.BRAIN-COMPUTER INTERFACE FOR LOWER LIMB EXOSKELETONS Assistive robotic technology has garnered significant attention from researchers and the public alike, especially in the realm of rehabilitation for individuals with physical disabilities, the elderly, and those recovering from injuries, including spinal cord damage.

Devices like lower limb exoskeletons and prosthetics play a crucial role in enhancing the quality of life for those who have lost mobility. A key consideration in the operation of these exoskeletons is the ability to interpret the user’s motion intentions effectively.

Electroencephalography (EEG) signals have emerged as a promising means to detect these intentions. Despite advancements in the control methods for lower limb exoskeletons using EEG signals over recent years, several challenges remain that require further exploration. This study examines the control mechanisms of lower body exoskeletons utilizing EEG signals, along with the challenges and potential of BrainComputer Interface (BCI) techniques in this field. The authors also present findings from their investigations to support the concept of controlling lower limb exoskeletons through EEG technology [42].

12.PROSTHESIS TESTING AND EVALUATION This article introduces an innovative design for a test bench-gait simulator intended for the evaluation of lower limb prostheses and their components, utilizing a Gough- Stewart platform equipped with six linear drives. This configuration enables the simulation of the prosthesis movements during testing, mimicking various user motor activities. In this setup, the GoughStewart platform employs EPCO linear drives produced

by Festo, which are managed through the industrial automation software “Controller Development System.”

The test bench is designed to assess the functionality of

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14.UNPOWERED EXOSKELETON FOR ASSISTANCE AND ENERGY HARVESTING

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GAIT

Powered exoskeletons are designed to assist with human locomotion; however, their bulky energy supply systems can be cumbersome for users. During walking, the human lower limbs alternate between acceleration and deceleration, during which positive and negative work is performed, respectively. By capturing the negative work done during deceleration, an assistive device can potentially enhance the acceleration phase of movement, leading to a reduction in overall metabolic expenditure. This study introduces a novel, unpowered flexible lower limb exoskeleton that parallels the user's legs, providing walking assistance without the need for an external power source. The exoskeleton mimics the anatomical structure of the human lower limb and incorporates elastic and damping components. When donned, it assists the muscles by harvesting kinetic energy during deceleration to facilitate subsequent acceleration, thus lowering biomechanical energy costs during walking.

Additionally, the generator within the exoskeleton acts as a damping mechanism, capable of converting kinetic energy into electricity to power wearable devices. A prototype of the flexible exoskeleton was developed, and experimental results confirmed its effectiveness, demonstrating a 3.12% reduction in metabolic cost at a walking speed of 4.5 km/h and generating a peak electrical output of 6.47 W at a speed of 5.1 km/h [43].

Fig-15.1 Motions Of Foot Planes[44].

16.BIOFEEDBACK FOR PROSTHETIC USERS

The precise solutions of equations exhibit notable parallels with minimizing error in control theory, suggesting that various control challenges can be interpreted through the lens of equation-solving. Neural dynamics models have emerged as a robust computational approach for tackling time-varying equations and optimization tasks due to their impressive convergence and stability. Within these models, the choice of activation function significantly influences their overall performance. This paper explores the use of a unique non- linear activation function, specifically the power-sum activation function, in the experimental simulation of lower limb motion intention recognition. By comparing it to traditional linear activation functions, the analysis highlights the enhanced convergence and robustness characteristics of the neural dynamics model utilizing the power-sum activation function, demonstrating its superior capabilities [44].

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Users of lower limb prosthetics often experience gait deviations, particularly in terms of asymmetrical stance time (ST), which can lead to additional musculoskeletal issues. To address this, biofeedback (BFB) systems offer promising solutions for gait training aimed at correcting these deviations. This study presents a wearable BFB system that provides vibrotactile feedback through two tactors positioned on both the anterior and posterior aspects of the residual limb for prosthetic users. The system aims to rectify asymmetrical ST (%) by employing two different feedback strategies: single threshold feedback (SF) and bandwidth threshold feedback (BF). The effectiveness of each strategy was validated with a group of five lower limb amputees by comparing gait trials[45] with feedback against trials without any feedback (NF). The results indicated significant differences between the NF and feedback trials. While no substantial differences were observed between SF and BF, there were noticeable trends suggesting that BF may promote ST (%) that aligns more closely with the target while minimizing error.

15.NEURAL DYNAMICS IN MOTION INTENTION RECOGNITION

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(torques) acting on the joints[47] throughout the recovery process. Utilizing the Lagrangian method, the dynamic equations governing the robot's motion were derived, and dynamic simulations were conducted using the SimMechanics tool, confirming the validity of the dynamic modelling. Furthermore, this approach allows for the convenient extraction of dynamic parameters for both the robot and human lower limbs once the motion control law is established. This provides a theoretical foundation for developing rehabilitation training strategies, analysing dynamic performance, and implementing precise force control.

Fig-16.1: Gait Pattern For Injuries People[45].

17.ELECTROMYOGRAPHY ANALYSIS IN HEALTHY AND AMPUTEE SUBJECTS Research on electromyography (EMG) has long compared the muscle activity of healthy individuals and amputees. This study specifically focused on recording EMG data from five healthy participants using the BIOPAC system with surface electrodes placed on muscles such as the biceps brachii, triceps, peroneus longus, and gastrocnemius, both with and without an additional weight of 5 kilograms.[46] Each subject performed various hand and leg movements, repeating each action four times. Additionally, EMG data from four amputees were analysed while they executed lower limb movements. Key parameters such as slope, peakto-peak value, mean, and area were extracted from the EMG signals to investigate potential differences between the two groups. Results indicated that the amplitude of the biceps and triceps in healthy subjects decreased over time under both weight conditions, reflecting muscle fatigue. Other parameters, including slope, mean, and area, also exhibited a decline over time. Comparatively, there were notable differences in EMG values for lower limb muscles between healthy individuals and amputees, attributed to the reduced muscle strength in phantom limbs. In healthy participants, the mean and amplitude values of clenches increased, indicating enhanced clench strength during the activities performed.

Fig-18.1Overview for custom AFOs[47]

19.LOWER LIMB REHABILITATION ROBOT WITH GAIT AND PLANTAR FORCE DATA This paper introduces a control scheme aimed at enhancing the safety and effectiveness of rehabilitation training for patients using a lower limb rehabilitation robot (LLRR), utilizing human gait data and plantar reaction force. Initially, normal human gait data captured through a motion capture platform (MCP) is inputted into the control system, while the plantar reaction force is processed and applied to the LLRR following dynamic[48] calculations. Subsequently, a controller is developed to track joint angles and angular velocity errors, facilitating accurate trajectory following.

The efficacy of this proposed method is validated through simulation results from a robot simulation model, demonstrating its potential for improving rehabilitation training outcomes.

18.REHABILITATION ROBOTICS AND MOTION DYNAMICS A novel horizontal rehabilitation robot for lower limbs has been developed based on a parallel mechanism, aligning with the motion patterns of lower limbs and principles of rehabilitation medicine. This robot is designed to assist patients with rehabilitation exercises targeting the hips, knees, and ankles. To ensure the safety and comfort of the affected limbs during training, it is essential to accurately understand the forces

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20.SEMI-PASSIVE INDUSTRIAL EXOSKELETON FOR SQUATTING ASSISTANCE

neurophysiological methods, especially the analysis of surface electromyography (SEMG) data, present a more objective and sensitive option. While much of the existing research has concentrated on upper limb spasticity, there remains a significant gap in the evaluation of lower limb spasticity. This study introduces a Bayesian-optimized[50] Support Vector Machine (SVM) classifier aimed at the objective assessment of lower limb spasticity through sEMG data.

In our experiment, we included seven participants categorized across four MAS levels, achieving an average recognition accuracy of over 75% with the optimal model and selected sEMG features. This innovative approach promises to enhance objectivity and accuracy in assessing lower limb spasticity, effectively mitigating the issues linked to subjective biases in traditional evaluation methods.

This paper introduces the E-LEG, an innovative semi- passive lower-limb exoskeleton designed to assist workers during squatting by allowing motorized adjustment of the assistive squatting height. Unlike traditional passive industrial exoskeletons, the E-LEG incorporates unique design elements, including an inertial sensor for measuring thigh tilt angle and an electromagnetic switch for modifying squat height, which significantly enhance its functionality. The paper not only details the design of the exoskeleton but also presents a systematic experimental evaluation involving human subjects. Through various assistance conditions, the study assessed the variability of muscular activity during prolonged static[49] squatting tasks. Metrics for evaluating the device's effects included leg muscle activity, plantar pressure fluctuations, the movement of the plantar pressure centre, and gait angles. The findings indicate that the E-LEG effectively reduces muscular activity during squatting while minimally impacting normal walking gait. Overall, this study demonstrates the potential of the E-LEG exoskeleton to alleviate muscular strain during extended squatting activities.

CONCLUSION The results of the research demonstrate the viability of combining 3D printing with composite materials in orthotic Lower limb design enhance patient outcomes reduce waste and customize for individual needs. The integration of lightweight, high-strength composites has shown promising results in reducing costs while maintaining the necessary strength for daily use.

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21.OBJECTIVE SPASTICITY ASSESSMENT USING MACHINE LEARNING

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Assessing lower limb spasticity is crucial for improving rehabilitation outcomes in stroke patients.

Traditional evaluation methods, such as the Modified Ashworth Scale (MAS), are often influenced by subjective biases, leading to inconsistent assessments among healthcare providers.

In contrast,

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Fig-20.1 Types Of Exoskeleton Based On Purpose[49].

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[11]. K. Nam and C. Crick, "Self-trainable 3D-printed prosthetic hands," 2021 30th IEEE International Conference on Robot & Human Interactive Communication (RO-MAN), Vancouver, BC, Canada, 2021, pp. 1196-1201, doi: 10.1109/RO-MAN50785.2021.9515506.

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