Shape memory polymer (SMP) is a new type of functional materials.SMP has lots of advantages such as low density,light weight,high shape-recovery rate and low cost,but its stiffness is low and shape recovery force is small.Therefore,the reinforced SMP composite has become a hot research focus.The latest progress of reinforced SMP composite is reviewed,with the emphasis placed on the analysis of the influence of reinforced materials on SMP properties including short fibers,particles and the mixture of fibers and particles.Finally,problems exist in the study and the prospect of reinforced SMP composite are discussed briefly.

A new type of testing system used for antithrombotic pressure circulatory equipment has been developed, which realized a new method for the calibration of pressure sensor. Multi-path control and acquisition functions are achieved by this method based on human-computer interaction testing system. The precision of pressure sensor is ob tained by polynomial fitting for each test point using linear interpolation method. The result showed that the precision test of pressure sensor could be realized easily and efficiently, using the developed testing system, and the parameters of pressure sensor could be calibrated effectively, so that it could be accurately used in the antithrombotic pressure circulatory equipment. The developed testing system has a prosperous future in the aspects of promotion and application.
Algorithms ; Calibration ; Equipment Design ; Humans ; Monitoring, Physiologic ; instrumentation ; Pressure ; Thrombosis ; diagnosis

In an anti-thrombotic pressure circulatory device, relays and solenoid valves serve as core execution units. Thus the therapeutic efficacy and patient safety of the device will directly depend on their performance. A new type of testing system for relays and solenoid valves used in the anti-thrombotic device has been developed, which can test action response time and fatigue performance of relay and solenoid valve. PC, data acquisition card and test platform are used in this testing system based on human-computer interaction testing modules. The testing objectives are realized by using the virtual instrument technology, the high-speed data acquisition technology and reasonable software design. The two sets of the system made by relay and solenoid valve are tested. The results proved the universality and reliability of the testing system so that these relays and solenoid valves could be accurately used in the antithrombotic pressure circulatory equipment. The newly-developed testing system has a bright future in the aspects of promotion and application prospect.
Equipment Design ; Humans ; Monitoring, Ambulatory ; instrumentation ; Pressure ; Reproducibility of Results ; Software ; Thrombosis ; diagnosis

BACKGROUND:Shape memory polymer is a new type of functional material. The applications of shape memory polymers in the biomedical field have increasingly been paid close attention. OBJECTIVE: To summarize the characteristics and applications of shape memory polymers. METHODS: SpringerLink and China Journal Ful text Database were searched for articles related to shape memory polymers. RESULTS AND CONCLUSION: As a new type of inteligence material, shape memory polymers have lots of advantages compared with shape memory aloy and shape memory ceramics, such as low density, light weight, low cost, high shape-recovery rate, easy to regulate the shape memory temperature, to dye, to shape and to be stimulated under expected switch temperature. Especialy for polyurethane, the structure-property relationships are extremely easy to control, the shape memory temperature can be set in a wide range from-30℃ to 70℃, and it has the biocompatibility. Due to these, shape memory polymers have great potentials in applications of biomedical engineering. But the comprehensive properties of the developed shape memory polymers are not satisfactory. For example, the polynorbornene has big recovery stress, fast recovery velocity and high recovery precision, but its relative molecular mass is very big, the molecularchain is long, and processing is difficult. Furthermore, most of shape memory polymers have smal recovery stress, slow recovery velocity, low recovery precision and unsatisfied repeat memory effect. The key problems for shape memory polymers include optimization of the function of shape memory and improvement of the comprehensive properties based on the technologies of molecular design and material modification.

PVC resin is widely used in medical and other industrial fields because of its good chemical corrosion resistance, wear resistance, low cost and simple production. In this study, the related research progress in the influence of resin polymerization degree, processing technology and processing aids on the mechanical properties of PVC was reviewed, and the influence rules of processing aids on the properties of PVC was analyzed. Relevant research results show that the increase of the resin polymerization degree can increase the strength of PVC, but at the same time reduce the toughness. The use of compression molding process is beneficial to improve the strength and modulus of PVC. The use of injection molding process is beneficial to improve the plasticity and toughness of the PVC. Properly increasing the processing temperature and the blending time can improve the toughness of PVC. Adding heat stabilizers can improve the plasticity, toughness and strength of PVC. Adding plasticizers can improve the strength and toughness of PVC. Adding modifiers can improve the strength and toughness of PVC.

Objective To analyze the influence of different materials on thermal stress field of the bipolar high-frequency electric knife. Methods The electric-thermal coupling simulation analysis was performed for thermal stress field in working process of the bipolar high-frequency electric knife. The influence patterns for 4 kinds of insulating layer materials 304 stainless steel, 316 stainless steel, 317 stainless steel, Ti6Al4V and 4 kinds of electrode materials polypropylene (PP), polyamide-6 (PA6), polycarbonate (PC) and acrylonitrile butadiene styrene (ABS) on thermal stress field and thermal deformation field of insulating layer, electrode and coating of bipolar high-frequency electric knife and myocardial tissues were studied. Results The thermal deformation of myocardial tissues was much higher than that of the components of high-frequency electric knife in period of 2 s for continuous power. In terms of myocardial tissue protection, 304 stainless steel was the best electrode material for high-frequency electric knife. For choosing PP as the insulating layer material, thermal deformation of myocardial tissues caused by thermal stress was the smallest, which could better maintain the integrity of myocardial tissues. Conclusions The manufacturing materials of high-frequency electric knife have an important influence on thermal stress field in its working process. The regularity analysis results can provide guidance for the development of high-frequency electric knife.

Objective To study the influence of hollow screws with five kinds of spatial distributions on the fixation effect of femoral neck fracture. Methods Geometric models of femoral neck fracture with Pauwels type I, II and III were built by reverse engineering according to CT images of the femur. Based on the finite element analysis software ANSYS, the stress distributions of internal fixation, head side and stem side of femoral neck and the displacement distributions of the model fixed by different methods were obtained. Results For femoral neck fracture with Pauwels type I, II and III, the maximum stresses at head side of femoral neck were the inverted triangle fixation method, two-screw parallel fixation method, two-screw parallel fixation method, respectively. The maximum stresses at stem side of femoral neck were the inverted triangle fixation method, inverted triangle fixation method and two-screw parallel fixation method, respectively. The minimum stresses on the screws were the cross fixation method, and the minimum displacements of the model were double-supported fixation method. Conclusions The probability of screw deformation and fracture is the smallest for cross fixation method. Inverted triangle fixation method can provide a good mechanical environment for fracture site. For femoral neck fracture with Pauwels typeⅠ and Ⅲ, double-supported fixation method has the strongest ability to prevent femoral neck shortening. While for femoral neck fracture with Pauwels typeⅡ, cross fixation method has the strongest ability to prevent femoral neck shortening.

Objective To analyze the influence regularities of different sizes on thermal stress field of bipolar high-frequency electric knife. Methods Based on the ANSYS software, the electric-thermal coupling simulation analysis was performed for thermal stress field of bipolar high-frequency electric knife during working. The effects of 3 different insulation layer thicknesses (0-5, 1-0, 1-5 mm), electrode thicknesses (0-5, 1-0, 1-5 mm) and coating thicknesses (3, 6, 9 μm) on thermal stress field of bipolar high-frequency electric knife were studied. Results If thickness of the insulation layer was larger, deformation of the myocardial tissues would be smaller due to thermal stress, that is, the thickness of the insulation layer was inversely proportional to thermal deformation of the myocardial tissue during working process of the high-frequency electric knife. For the 3 electrode thicknesses, 1-0 mm was a better choice. And for the 3 coating thicknesses, 6 μm was a better choice. Conclusions The component sizes for the high-frequency electric knife have an important influence on thermal stress field, and the result can provide guidance for design of the high-frequency electric knife.

To solve the problems of small one-time ablation range and easy charring of the tissue around the electrode associated with the tumor radiofrequency ablation needle, based on the multiphysical field coupling analysis software COMSOL, the effects of needle material, the number of sub needles and the bending angle of sub needles on the ablation effect of radiofrequency ablation electrode needle were studied. The results show that compared with titanium alloy and stainless steel, nickel titanium alloy has better radiofrequency energy transmission efficiency and it is the best material for electrode needle. The number of sub needles has a great influence on the average necrosis depth and the maximum necrosis diameter. Under the same conditions, the more the number of sub needles, the larger the volume of coagulation necrosis area. The bending angle of the needle has a great effect on the maximum diameter of the coagulated necrotic area, but has little effect on the average necrotic depth. Under the same other conditions, the coagulation necrosis area formed by ablation increased with the increase of the bending angle of the sub needle. For the three needles with bending angles of 60 °, 90 ° and 120 ° analyzed in this paper, the one with bending angle of 120 ° can obtain the largest coagulation necrosis area. In general, the design of nickel titanium alloy with 120 ° bending 8-pin is the optimal. The average depth of radiofrequency ablation necrosis area is 32.40 mm, and the maximum necrosis diameter is 52.65 mm. The above optimized design parameters can provide guidance for the structure and material design of tumor radiofrequency ablation needle.
Humans ; Needles ; Temperature ; Catheter Ablation/methods* ; Necrosis ; Neoplasms/surgery* ; Alloys

Objective To analyze the influence from size parameters of minimally invasive vascular clamp on mechanical properties of small arteries. Methods The finite element simulation analysis on the process of minimally invasive vascular clamp clamping small arteries was performed. The influence patterns of 5 different sawtooth spacing, sawtooth heights and sawtooth lengths on mechanical properties of small arteries were studied. Results Larger sawtooth spacing led to smaller maximum equivalent stress of the clamped artery. The maximum equivalent stress of the small artery was not linear with the sawtooth height of the vascular clamp. The maximum equivalent stress of the small artery was the smallest and the vascular injury was the minimal when the swatooth height was 75 μm. The sawtooth length of the vascular clamp had an important influence on mechanical properties of clamped small arteries. The maximum equivalent stress of the artery was proportional to the sawtooth length of the vascular clamp. Conclusions The size parameters of minimally invasive vascular clamp had an important influence on mechanical properties in the process of clamping small arteries. The research findings can provide guidance for the design of the minimally invasive vascular clamp.