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Injection Molding Microstructures

Abstract -- Plastics have so far played only a subordinate role in the multibillion-dollar Microsystem industry. The commercial breakthrough strongly depends on means of low cost mass fabrication with dimensional accuracy and good part quality. Widely used mass-production methods of polymeric materials such as injection molding, however, require significant modification to adapt to micro molding application. One of the hurdles limiting the current technical capability in micro injection molding is that the molten polymer in a tiny cavity instantaneously freezes upon contacting the relatively cold cavity wall. The problem gets worse when micro features with higher aspect ratio are to be molded. The main objective of the proposed research is to develop a novel technology for successful micro injection molding with respect to lower cycle time, better replication and better mechanical and optical quality as compared to the existing technology. This objective will be accomplished by rapidly heating the mold surface so that the melt can fill the cavity isothermally and yet be processed within the normal injection molding cycle time. This isothermal filling not only facilitates complete filling of high-aspect-ratio micro features with lower melt temperature and slower filling rate than those currently used but is also expected to improve dimensional accuracy and mechanical and optical properties of micro-featured articles. Development of the integrated technology capable of replicating high-aspect-ratio micro features with lateral dimension less than 20 nm will push the current technical envelope of micro injection molding further into those areas that have so far predominated by etching- and lithography- based fabrications.  

a) Conventional molding

b) RTR molding

 

            

c) Metal Micro Gear Mold Insert                                    d) HDPE Micro Gear

 

            

e) AnoporeŽ aluminum oxide membrane (top and side views)

 

             

f) Nano posts made from polystyrene injected into AnoporeŽ  membrane (top and side views)

 

g) Magnified image of polystyrene nano post connection to base

 

h) Side view of wire EDM stainless steel micro well embossing insert

 

     

i) Micro well embossing insert (top view)    j) HDPE embossed micro wells

 

       

k) Hexagonal micro well embossing insert (Mezzo Systems Inc.) and HDPE embossed hexagonal micro wells