Sugeng Supriadi

PDMS Surface Modification Using Biomachining Method for Biomedical Application

Engineering a cell-friendly material in a form of lab-on-chip is the main goal of this study. The chip was made of polydimethyl siloxane (PDMS) with a surface modification to realize a groovy structure on its surface. This groovy surface was naturally and randomly designed via biomachining process. This measure was aimed to improve the cell attachment on the PDMS surface that always known as hydrophobic surface. The biomachined surface of mold and also products were characterized as surface roughness and wettability. The result shows that the biomachining process were able to be characterized in three classes of roughness on the surface of PDMS.

Sintering of Stainless Steel Nanopowders for Micro-Component Part Applications

Micro Metal Injection Molding utilizing 316 steel nanopowder with 100 nm in mean size was investigated to fabricate micro part. The nanopowder was used since its advantages to produce better surface roughness and detail structure in the micro part fabrication. During nanopowder preparation, thin oxide must be formed intentionally to avoid powder burnt before its exposed to the air during mixing with the wax binder system. Unfortunately, this oxide still exist after sintering and decrease the mechanical properties (ductility and densification) by the formation of secondary phase which detected as chrome oxide. In this paper, deep elaboration for oxide characteristics and the ways to reduce it by vary the sintering parameters and in Hydrogen atmosphere were described briefly. Here, we infer by reducing the heating rate, increasing the sintering temperature and utilizing the Hydrogen atmosphere can be effectively optimize the utilizing of nanopowder for micro part fabrication.

The experiment of magnesium ECAP miniplate as alternative biodegradable material (on male white New Zealand rabbits)

Study of biodegradations of Magnesium ECAP (Equal Channel Angular Pressing) miniplate in the osteosynthesis system has been used as a new material for plate and screw in oral and maxillofacial surgery. This miniplate and screw that were made of Magnesium ECAP were implanted in the femurs of New Zealand rabbits. The degradation process was detected through pocket gas that appeared in hard and soft tissues surrounding in the implanted miniplates and screws. From the changes on the tissues, we can assess the biodegradation process by measuring the gas pocket through micro-CT Scan. Upon the first month of study we euthanized the rabbits and made a micro-CT Scan to see how far the effect of the gas pocket was. Histological analyses were performed to investigate the local tissue response adjacent to the Magnesium ECAP miniplates. We analyzed the femur of a rabbit a month, three months, and five months after implantation. The result showed a degradation rate in the implanted Magnesium ECAP miniplate of 0.61±0.39 mm/year. Unlike the screws, miniplates have higher water content and blood flow than bone, therefore they degrade faster. This study shows promising results for further development of Magnesium ECAP and in the production of osteosynthesis material for rigid fixation in Oral and Maxillofacial skeleton.Study of biodegradations of Magnesium ECAP (Equal Channel Angular Pressing) miniplate in the osteosynthesis system has been used as a new material for plate and screw in oral and maxillofacial surgery. This miniplate and screw that were made of Magnesium ECAP were implanted in the femurs of New Zealand rabbits. The degradation process was detected through pocket gas that appeared in hard and soft tissues surrounding in the implanted miniplates and screws. From the changes on the tissues, we can assess the biodegradation process by measuring the gas pocket through micro-CT Scan. Upon the first month of study we euthanized the rabbits and made a micro-CT Scan to see how far the effect of the gas pocket was. Histological analyses were performed to investigate the local tissue response adjacent to the Magnesium ECAP miniplates. We analyzed the femur of a rabbit a month, three months, and five months after implantation. The result showed a degradation rate in the implanted Magnesium ECAP miniplate of 0.61±0.39...

Biomarker selection for determining bone biocompatibility of pure magnesium processed by equal channel angular pressing (ECAP) using immunohistochemistry

Since grain refinement is proved to be favorable to improve mechanical properties and corrosion resistance, a new conceptual metal forming process, equal channel angular pressing (ECAP), has been carried out on magnesium, a very promising biodegradable material in the field of oral and maxillofacial surgery. The popularity of immunohisto-chemistry (IHC) has been rising following the discovery of biomarker. In the meantime, more antibodies being produced for research have been continuously rising and becoming more varied. This review provides a conceptual framework to understand the roles of IHC on determination of bone biocompatibility to ECAP magnesium by selecting biomarker and point needed to either select or make an antibody to the target. From the review, it has been concluded that the most suitable biomarkers for biocompatibility test of bone implanted with ECAP magnesium are collagen-1, osteocalcin, smooth muscle actin, and CD68.Since grain refinement is proved to be favorable to improve mechanical properties and corrosion resistance, a new conceptual metal forming process, equal channel angular pressing (ECAP), has been carried out on magnesium, a very promising biodegradable material in the field of oral and maxillofacial surgery. The popularity of immunohisto-chemistry (IHC) has been rising following the discovery of biomarker. In the meantime, more antibodies being produced for research have been continuously rising and becoming more varied. This review provides a conceptual framework to understand the roles of IHC on determination of bone biocompatibility to ECAP magnesium by selecting biomarker and point needed to either select or make an antibody to the target. From the review, it has been concluded that the most suitable biomarkers for biocompatibility test of bone implanted with ECAP magnesium are collagen-1, osteocalcin, smooth muscle actin, and CD68.

Surface characteristics of Ti6Al4V-EDM implant engineered by PVD coated-etching and Acidithiobacillus ferrooxidans based-biomachining

Presented study aims to characterize the surface implant engineered by PVD (Physical Vapor Deposition) coated-etching and biomachining. The material used is Ti6Al4V manufactured by electrical discharge machining (EDM). Copper (Cu) was used as its electrode material. The results show that acid etching and it followed by PVD coating (ΔRa 51%) were able to decrease the average of surface roughness (Ra) of original EDM to moderately rough category compared to biomachined samples (ΔRa 31%). SEM and EDS observations indicated that Acidithiobacillus ferrooxidans were not capable of removing Cu effectively in its condition as a contaminant on the Ti6Al4V surface. Moreover, significant increasing of the percentage of element weight (wt%) of Oxygen (O) generated by the biomachining can be applied as an alternative to the PVD coating (wt% O 8,9) to enhance the bioactivity of the etched implant. On the other hand, the contact angles generated by the biomachined samples prove that the surface is hydrophobic in nature that prone to increase cell attachment than the hydrophilic surface generated by PVD coated-etching.

Examination of Biodegradable Magnesium Screw Processed by Equal Channel Angular Pressing: A Novel In Vivo Study in Rabbits

Magnesium alloys have shown potential as biodegradable metallic materials for oral and maxillofacial surgery applications due to their degradability. Biodegradable magnesium are advantageous over existing biodegradable materials such as polymers, ceramics and bioactive glasses in load-bearing applications where sufficient strength and Young’s modulus close to that of the bone are required.

Battery thermal management system using loop heat pipe with LTP copper capillary wick

Loop heat pipes (LHPs) with Lotus-Type Porous Copper (LTP Copper) capillary wick are expected to be applied to battery thermal management systems for safe operation at high performance with a long service life. Sintered LTP Copper is a high permeability porous metal with an excellent capillary pumping characteristic. The objective of this work is to determine the performance of the battery thermal management system using LHP with sintered LTP Copper capillary wick experimentally. The experiment used two battery simulators made of aluminum. The heat generation of the battery was simulated using cartridge heaters. The LHP was made of 10 m OD copper tube, and the sintered LTP Copper capillary wick was placed in the liquid line. Water was used as working fluid with filling ratio of 50%. The evaporator section of the LHP was inserted between the battery simulators surfaces. A thermostatic bath was used to regulate the condenser cooling fluid temperature. K-type 0.3 mm thermocouples were used for temperature measurement, and a digital power meter was used to measure the electric power. Experiments were conducted with various heating power with the condenser cooling fluid temperature was kept at 28°C. At a heat generation of 20 W, the LHP was capable of maintaining the battery surface temperature below 50°C. At a heat generation of 40 W, the utilization of LHP with LTP Copper can reduce the average battery simulator surface temperature from 93°C to 65°C.

Vacuum Sintering Process in Metal Injection Molding for 17-4 PH Stainless Steel as Material for Orthodontic Bracket

Malocclusion is one of the common problems encountered in the teeth and mouth of Indonesian people. This country is also confronted with problems that the bracket have to been imported from abroad. The purpose of this study is to produce national orthodontic bracket by metal injection molding (MIM) process in Indonesia, particularly by using vacuum sintering for 17-4 PH stainless steel because it is a material commonly used for orthodontic bracket. Sintering conducted at four different temperatures, at 1320 °C, 1340 °C, 1360 °C, and 1380 °C. The results showed that there are inclusions in sintering products. The relative density increases with increasing temperature sintering because the area of porosity are reduced. In addition, the results of sintering at 1360 °C has optimal hardness, which is amounted to 395 HV and higher than commercial bracket.

Thermal Debinding Process of SS 17-4 PH in Metal Injection Molding Process with Variation of Heating Rates, Temperatures, and Holding Times

Generally, metal injection molding (MIM) method utilizes SS 17-4 PH as material for application of orthodontic bracket. One of the process of MIM is thermal debinding, which binder is eliminated by thermal energy. In this study, thermal debinding process is conducted with variation of temperature, i.e. 480, 510, and 540°C, holding time, i.e. 0.5, 1 and 2 hours, heating rate, i.e. 0.5, 1, 1.5, and 2°C/min.The effect of temperature shows that the increased temperature will result in the mass reduction percentage due to formation of oxide on the sample, which will be proven through TGA testing. The highest mass reduction was 6.4137 wt% which was obtained at 480°C. For the variation of holding time, the longer the holding time will result in increased mass reduction and the highest mas reduction was 6.255 wt% which was obtained during 2 hours of holding time. For the heating rate, the slower the heating rate will result in increased mass reduction and decreased the presence of crack formation. The best variable was obtained at heating rate of 0.5°C/min, which resulted mass reduction of 6.2488 wt% and less crack formation.

Orthopaedic jack for scoliosis surgery purposes: Concept and design

Scoliosis surgery is one of the most difficult orthopedic surgery that have been committed today as the failure rate of orthopedic surgery for adult patients is 15%. Aside from the long duration of surgery, this surgical failure is caused by failure in biomedical instrumentation. Furthermore, this kind of failure is causing inefficiency of the surgery. With current known orthopedic surgery method, three surgeons are needed in a single orthopedic surgery. In fact, a single surgery can take up to 8 hours to be done, which increases the risk of surgical failure. Based on this problem, authors hope that our orthopedic jacks could solve the problem.