Effect of tensile deformation on the optoelectronic properties of black phosphine-doped lithium atoms.

CONTEXT: First-principles calculations based on the generalized gradient approximation gradient and the Perdew-Burke-Ernzerhof function (GGA-PBE generalized function) are carried out on the intrinsic and lithium-doped black phosphine systems to investigate the effects of different uniaxial tensile deformations on the electronic and optical properties of the systems. It is shown that the structural stability of the intrinsic and lithium-doped systems decreases with increasing tensile deformation, and all systems are most stable at 0% tensile deformation. The intrinsic black phosphazene system is a direct band gap semiconductor, and its band gap increases and then decreases with tensile deformation and reaches a maximum value of 1.086 eV at 4%. Lithium doping closes the band gap of the black phosphazene system, which is metallic in nature, but the band gap is opened up when the tensile deformation is 4-6%. From the density of states analysis, the density of states of all systems is basically contributed by the s and p orbitals, with little contribution from the d orbitals, and the contribution from the p orbitals is dominant. From the analysis of optical properties, the increase of tensile deformation causes the absorption peaks of the intrinsic system to redshift then blueshift then redshift, causes the absorption peaks of the lithium-doped system to redshift, and causes the reflection peaks of all systems to redshift. In addition, lithium doping blueshifts the absorption and reflection peaks of the systems compared to the intrinsic black phosphazene system. METHODS: Using the CASTEP section of the Materials Studio software, first-principle calculations based on density functional theory are done on the top-site doped lithium atoms of monolayer black phosphine under uniaxial stretching deformation in the a-direction, and the generalized gradient approximation gradients and Perdew-Burke-Ernzerhof functions (GGA-PBE generalized functionals) are used for the optimization and approximation process. The optimization parameters are set for the supercell structure: its plane-wave truncation energy is set to 400 eV, its Brillouin zone K-point grid is set to 3*3*3, its self-consistent field iteration accuracy convergence value is 2.0e-6 eV/atom, the convergence basis of its structural optimization is 0.02 eV/ Å, and the convergence of the stress value is 0.05 gpa. During the optimization period, the interaction force between atoms is 0.03 eV/ Å and the atomic displacement is less than 0.001 Å. To eliminate the effect of interlayer forces, a vacuum layer with a thickness of 15 Å is placed in its vertical direction (i.e., c-axis direction).

Collaborative Control Method and Experimental Research on Robot-Assisted Craniomaxillofacial Osteotomy Based on the Force Feedback and Optical Navigation.

OBJECTIVE: Surgical robot has advantages in high accuracy and stability. But during the robot-assisted bone surgery, the lack of force information from surgical area and incapability of intervention from surgeons become the obstacle. The aim of the study is to introduce a collaborative control method based on the force feedback and optical navigation, which may optimally combine the excellent performance of surgical robot with clinical experiences of surgeons. MATERIALS AND METHODS: The CMF ROBOT system was integrated with the force feedback system to ensure the collaborative control. Force-velocity control algorithm based on force feedback was designed for this control method. In the preliminary experimental test, under the collaborative control mode based on force feedback and optical navigation, the craniomaxillofacial surgical robot entered the osteotomy line area according to the preoperative surgical plan, namely, right maxillary Le Fort I osteotomy, left maxillary Le Fort I osteotomy, and genioplasty. RESULTS: The force sensor was able to collect and record the resistance data of the cutting process of the robot-assisted craniomaxillofacial osteotomy assisted in real time. The statistical results showed that the repeatability of collaborative control mode was acceptable in bilateral maxillary Le Fort I osteotomies (right, P =0.124>0.05 and left, P =0.183>0.05) and unfavorable in genioplasty ( P =0.048<0.05). CONCLUSION: The feasibility of robot-assisted craniomaxillofacial osteotomy under the collaborative control method based on the force feedback and optical navigation was proved in some extent. The outcome of this research may improve the flexibility and safety of surgical robot to meet the demand of craniomaxillofacial osteotomy.

Error Analysis of Robot-Assisted Orthognathic Surgery.

OBJECTIVE: Orthognathic surgery is an effective method to correct the dentomaxillofacial deformities. The aim of the study is to introduce the robot-assisted orthognathic surgery and demonstrate the accuracy and feasibility of robot-assisted osteotomy in transferring the preoperative virtual surgical planning (VSP) into the intraoperative phase. METHODS: The CMF robot system, a craniomaxillofacial surgical robot system was developed, consisted of a robotic arm with 6 degrees of freedom, a self-developed end-effector, and an optical localizer. The individualized end-effector was installed with reciprocating saw so that it could perform osteotomy. The study included control and experimental groups. In control group, under the guidance of navigation system, surgeon performed the osteotomies on 3 skull models. In experimental group, according to the preoperative VSP, the robot completed the osteotomies on 3 skull models automatically with assistance of navigation. Statistical analysis was carried out to evaluate the accuracy and feasibility of robot-assisted orthognathic surgery and compare the errors between robot-assisted automatic osteotomy and navigation-assisted manual osteotomy. RESULTS: All the osteotomies were successfully completed. The overall osteotomy error was 1.07 ±â€Š0.19 mm in the control group, and 1.12 ±â€Š0.20 mm in the experimental group. No significant difference in osteotomy errors was found in the robot-assisted osteotomy groups (P = 0.353). There was consistence of errors between robot-assisted automatic osteotomy and navigation-assisted manual osteotomy. CONCLUSION: In robot-assisted orthognathic surgery, the robot can complete an osteotomy according to the preoperative VSP and transfer a preoperative VSP into the actual surgical operation with good accuracy and feasibility.