# Current State of Robotics in Hand Rehabilitation after Stroke: A Systematic Review
## 2 Materials and Methods
### The Development of Hand Rehabilitation Robot
#### 2.1.2 The End-Effector Hand Rehabilitation Robot  
The end-executing hand rehabilitation robot is connected to the patient's hand at a distal point with joints that do not match the joints of the human hand. The forces generated at the distal interface change the position of other joints simultaneously, making it difficult for individual joints to move individually [26; 27]. This paper focuses on driven hand rehabilitation robots, which have been developed over the past 30 years and have become more mature in technology. There are still a lot of researchers in the innovative research, the following will introduce several new end-effector hand rehabilitation robots. In 2015, the Robotics Laboratory of Seoul National University developed the Exo-Glove Poly, a wearable glove powered by tendons, which is a breakthrough from the rigid structure of previous gloves The Exo-Glove Poly has a built-in controller that receives electrical signals from the user's brain and then drives the three fingers of the flexible glove via a motor. Figure 5a shows a flexible glove made of polymer with two tendons on each finger, one on the dorsal side simulating the finger extensor tendon for finger extension and one across the ulnar and radial sides simulating the deep finger flexor for finger flexion [38; 39; 40; 41; 42]. The National University of Singapore has designed a flexible rehabilitation glove, shown in Figure 5b, which is pneumatically actuated. The main purpose of this rehabilitation hand is to help stroke and hemiplegic patients to stretch their hands to help restore muscles and prevent spasticity. The rehabilitation glove has an airbag on the back of each finger, and the airbag is driven to stretch the finger by punching air pressure into the airbag [43]. The device is simple in construction, lightweight in mass, and suitable for rehabilitation of patients with severe hemiplegia, but the rehabilitation hand is single-functional, enabling only hand extension, and the pneumatic needs to be supplied with an air pump, which limits portability and is noisy. Harvard University has designed a pneumatically actuated intelligent hand rehabilitation glove, shown in Figure 5c, which assists stroke and hemiplegic patients with hand extension and grasping movements. A new pneumatic actuator is implanted on the back of each finger of the rehabilitation glove to drive the finger movement. The actuator is made of two elastic materials with different stretching properties sewn together, and due to the different stretching properties, the actuator will bend and stretch during the process of inflation and deflation and drive the finger movement at the same time, and the bending mode of the actuator will change with different sewing modes of the materials [44; 45]. The rehabilitation glove also has various sensors implanted in it, and patients can perform rich human-computer interaction rehabilitation training under the guidance of doctors after wearing it to help stroke and hemiplegic patients to have better rehabilitation. In 2016, [PERSON] et al. [46] developed a portable, actuated glove-orthosis, allowing free movement of each joint, as the abductor tendon's cable runs through a cable guide attached to the dorsal side of the glove, as shown in Figure 6. The guides form a bridge over each joint to allow joint flexion but prevent hyperextension of the joint. They are made of glass-filled nylon, using a selective laser sintering technique (SLS), and are sewn into each glove. For each finger, the single cable from the corresponding actuator is split into three cables to pass through the guides in order to provide greater lateral stability. Linear servo actuators (L12, Firgelli Technologies, Inc., based in Victoria, BC, Canada) move the cables to generate extended torque at each joint of the finger.