this information to a microcontroller located inside the device, and processes feedback from the limb and actuator, e.g., position or force, and sends it to the controller. examples include surface electrodes that detect electrical activity on the skin, needle electrodes implanted in muscle, or solid-state electrode arrays with nerves growing through them. one type of these biosensors are employed in myoelectric prostheses. a device known as the controller is connected to the user's nerve and muscular systems and the device itself. it sends intention commands from the user to the actuators of the device and interprets feedback from the mechanical and biosensors to the user. the controller is also responsible for the monitoring and control of the movements of the device. an actuator mimics the actions of a muscle in producing force and movement. examples include a motor that aids or replaces original muscle tissue. targeted muscle reinnervation (tmr) is a technique in which motor nerves, which previously controlled muscles on an amputated limb, are surgically rerouted such that they reinnervate a small region of a large, intact muscle, such as the pectoralis major. as a result, when a patient thinks about moving the thumb of their missing hand, a small area of muscle on their chest will contract instead. by placing sensors over the reinnervated muscle, these contractions can be made to control the movement of an appropriate part of the robotic prosthesis. a variant of this technique is called targeted sensory reinnervation (tsr). this procedure is similar to tmr, except that sensory nerves are surgically rerouted to skin on the chest, rather than motor nerves rerouted to muscle. recently, robotic limbs have improved in their ability to take signals from the human brain and translate those signals into motion in the artificial limb. darpa, the pentagon's research division, is working to make even more advancements in this area. their desire is to create an artificial limb that ties directly into the nervous system. robotic arms advancements in the processors used in myoelectric arms have allowed developers to make gains in fine-tuned control of the prosthetic. the boston digital arm is a recent artificial limb that has taken advantage of these more advanced processors. the arm allows movement in five axes and allows the arm to be programmed for a more customized feel. recently the i-limb hand, invented in edinburgh, scotland, by david gow has become the first commercially available hand prosthesis with five individually powered digits. the hand also possesses a manually rotatable thumb which is operated passively by the user and allows the hand to grip in precision, power, and key grip modes. another neural prosthetic is johns hopkins university applied physics laboratory proto 1. besides the proto 1, the university also finished the proto 2 in 2010. early in 2013, max ortiz catalan and rickard brånemark of the chalmers university of technology, and sahlgrenska university hospital in sweden, succeeded in making the first robotic arm which is mind-controlled and can be permanently attached to the body (using osseointegration). an approach that is very useful is called arm rotation which is common for unilateral amputees which is an amputation that affects only one side of the body; and also essential for bilateral amputees, a person who is missing or has had amputated either both arms or legs, to carry out activities of daily living. this involves inserting a small permanent magnet into the distal end of the residual bone of subjects with upper limb amputations. when a subject rotates the residual arm, the magnet will rotate with the residual bone, causing a change in magnetic field distribution. eeg (electroencephalogram) signals, detected using small flat metal discs attached to the scalp, essentially decoding human brain activity used for physical movement, is used to control the robotic limbs. this allows the user to control the part directly. robotic transtibial prostheses the research of robotic legs has made some advancement over time, allowing exact movement and control. researchers at the rehabilitation institute of chicago announced in september 2013 that they have developed a robotic leg that translates neural impulses from the user's thigh muscles into movement, which is the first prosthetic leg to do so. it is currently in testing. hugh herr, head of the biomechatronics group at mit's media lab developed a robotic transtibial leg (powerfoot biom). the icelandic company össur has also created a robotic transtibial leg with motorized ankle that moves through algorithms and sensors that automatically adjust the angle of the foot during different points in its wearer's stride. also there are brain-controlled bionic legs that allow an individual to move his limbs with a wireless transmitter. prosthesis design the main goal of a robotic prosthesis is to provide active actuation during gait to improve the biomechanics of gait, including, among other things, stability, symmetry, or energy expenditure for amputees. there are several powered prosthetic legs currently on the market, including fully powered legs, in which actuators directly drive the joints, and semi-active legs, which use small amounts of energy and a small actuator to change the mechanical properties of the leg but do not inject net positive energy into gait. specific examples include the empower from bionx, the proprio foot from ossur, and the elan foot from endolite. various research groups have also experimented with robotic legs over the last decade. central issues being researched include designing the behavior of the device during stance and swing phases, recognizing the current ambulation task, and various mechanical design problems such as robustness, weight, battery-life/efficiency, and noise-level. however, scientists from stanford university and seoul national university has developed artificial nerves system that will help prosthetic limbs feel. this synthetic nerve system enables prosthetic limbs sense braille, feel the sense of touch and respond to the environment. use of recycled materials prosthetics are being made from recycled plastic bottles and lids around the world. attachment to the body most prostheses can be attached to the exterior of the body, in a non-permanent way. some others however can be attached in a permanent way. one such example are exoprostheses (see below). direct bone attachment and osseointegration main article: osseointegration osseointegration is a method of attaching the artificial limb to the body. this method is also sometimes referred to as exoprosthesis (attaching an artificial limb to the bone), or endo-exoprosthesis. the stump and socket method can cause significant pain in the amputee, which is why the direct bone attachment has been explored extensively. the method works by inserting a titanium bolt into the bone at the end of the stump. after several months the bone attaches itself to the titanium bolt and an abutment is attached to the titanium bolt. the abutment extends out of the stump and the (removable) artificial limb is then attached to the abutment. some of the benefits of this method include the following: better muscle control of the prosthetic. the ability to wear the prosthetic for an extended period of time; with the stump and socket method this is not possible. the ability for transfemoral amputees to drive a car. the main disadvantage of this method is that amputees with the direct bone attachment cannot have large impacts on the limb, such as those experienced during jogging, because of the potential for the bone to break. cosmesis cosmetic prosthesis has long been used to disguise injuries and disfigurements. with advances in modern technology, cosmesis, the creation of lifelike limbs made from silicone or pvc, has been made possible. such prosthetics, including artificial hands, can now be designed to simulate the appearance of real hands, complete with freckles, veins, hair, fingerprints and even tattoos. custom-made cosmeses are generally more expensive (costing thousands of u.s. dollars, depending on the level of detail), while standard cosmeses come premade in a variety of sizes, although they are often not as realistic as their custom-made counterparts. another option is the custom-made silicone cover, which can be made to match a person's skin tone but not details such as freckles or wrinkles. cosmeses are attached to the body in any number of ways, using an adhesive, suction, form-fitting, stretchable skin, or a skin sleeve. cognition unlike neuromotor prostheses, neurocognitive prostheses would sense or modulate neural function in order to physically reconstitute or augment cognitive processes such as executive function, attention, language, and memory. no neurocognitive prostheses are currently available but the development of implantable neurocognitive brain-computer interfaces has been proposed to help treat conditions such as stroke, traumatic brain injury, cerebral palsy, autism, and alzheimer's disease. the recent field of assistive technology for cognition concerns the development of technologies to augment human cognition. scheduling devices such as neuropage remind users with memory impairments when to perform certain activities, such as visiting the doctor. micro-prompting devices such as peat, ablelink and guide have been used to aid users with memory and executive function problems perform activities of daily living. prosthetic enhancement sgt. jerrod fields, a u.s. army world class athlete program paralympic sprinter hopeful, works out at the u.s. olympic training center in chula vista, calif. a below-the-knee amputee, fields won a gold medal in the 100 meters with a time of 12.15 seconds at the endeavor games in edmond, ok, on june 13, 2009 in addition to the standard artificial limb for everyday use, many amputees or congenital patients have special limbs and devices to aid in the participation of sports and recreational activities. within science fiction, and, more recently, within the scientific community, there has been consideration given to using advanced prostheses to replace healthy body parts with artificial mechanisms and systems to improve function. the morality and desirability of such technologies are being debated by transhumanists, other ethicists, and others in general. body parts such as legs, arms, hands, feet, and others can be replaced. the first experiment with a healthy individual appears to have been that by the british scientist kevin warwick. in 2002, an implant was interfaced directly into warwick's nervous system. the electrode array, which contained around a hundred electrodes, was placed in the median nerve. the signals produced were detailed enough that a robot arm was able to mimic the actions of warwick's own arm and provide a form of touch feedback again via the implant. the deka company of dean kamen developed the "luke arm", an advanced nerve-controlled prosthetic. clinical trials began in 2008, with fda approval in 2014 and commercial manufacturing by the universal instruments corporation expected in 2017. the price offered at retail by mobius bionics is expected to be around $100,000. further research in april 2019, there have been improvements towards prosthetic function and comfort of 3d-printed personalized wearable systems. instead of manual integration after printing, integrating electronic sensors at the intersection between a prosthetic and the wearer's tissue can gather information such as pressure across wearer's tissue, that can help improve further iteration of these types of prosthetic. oscar pistorius in early 2008, oscar pistorius, the "blade runner" of south africa, was briefly ruled ineligible to compete in the 2008 summer olympics because his transtibial prosthesis limbs were said to give him an unfair advantage over runners who had ankles. one researcher found that his limbs used twenty-five percent less energy than those of a non-disabled runner moving at the same speed. this ruling was overturned on appeal, with the appellate court stating that the overall set of advantages and disadvantages of pistorius' limbs had not been considered. pistorius did not qualify for the south african team for the olympics, but went on to sweep the 2008 summer paralympics, and has been ruled eligible to qualify for any future olympics. he qualified for the 2011 world championship in south korea and reached the semi-final where he ended last timewise, he was 14th in the first round, his personal best at 400m would have given him 5th place in the finals. at the 2012 summer olympics in london, pistorius became the first amputee runner to compete at an olympic games. he ran in the 400 metres race semi-finals, and the 4 × 400 metres relay race finals. he also competed in 5 events in the 2012 summer paralympics in london. design considerations there are multiple factors to consider when designing a transtibial prosthesis. manufacturers must make choices about their priorities regarding these factors. performance nonetheless, there are certain elements of