| The ultrasonic bonding technology of the polymer microfluidic chip has broad application prospects due to its advantages of high bonding strength,high efficiency,and excellent biocompatibility.However,it is difficult and complicated to fabricate the energy joint structure applied in the ultrasonic bonding technology at present.The microchannel is easily clogged by the fusion.The bonding process is also difficult to control.At the same time,the problems are still obvious about the jigs using in the ultrasonic bonding,such as the poor leveling ability and low efficiency.In vie w of the above problems,this paper conducted the following research:(1)A kind of chip energy joint structure was designed,which consisted of three main parts: the director protrusion,the bonding pool and the bonding limited platform.The energy joint structure was integrated with the liquid storage area,the micro mixing area,the delay area,the detection area and the buffer waste area on the PMMA substrate.The cover is a PMMA flat that only has an injection port.Its diameter is 3 mm.The substrates of experimental chips were fabricated by hot embossing.The hot embossing silicone mould was made by the dry-etching processes.Hot embossing parameters were optimized and the substrates were hot embossed.After the hot embossing process,the size,3D morphology of the energy joint structure and surface roughness of the microchannels were measured and tested respectively.The precision of the director protrusion is about 95.4%,which meets the requirements of the experiment.(2)Considering the characteristics of ultrasonic bonding,the self-balancing jig was designed.The self-balancing jig mainly includes two parts: the chip clamp plate and the self-balancing de vice.The main functions of the chip clamp plate include the positioning of the chip before the bonding,the clamping of the chip in the bonding process and the prying of the chip after the bonding.The pressure self-balancing device adopted the form of a spherical pair,which can realize the passive leveling between the ultrasonic head and the chip.In order to verify the leveling performance of the self-balancing jig,a jig with no adjustment function was used as contrast experiment.The prescale film was used to measure and scanned into the MATLAB.The pressure distribution coefficient M and the pressure distribution ratio ? were defined.The results showed that self-balancing jig can increased the pressure distribution ratio ? about 35.20%-43.18%.(3)The experimental chip was bonded,and the energy joint structure of the chip was verified.By changing the bonding time,the cross section of the experimental chips were observed and measured by scanning electron microscope(SEM),and the melting curve of the height of the director protrusion was brought.The results showed that the energy joint structure didn't block the microchannels.At the same time,with the increasing of bonding time,the height of director protrusion had obvious "stagnation phase ".The height of microchannels was equal in this "stagnation phase ",which can achieve effective control in the ultrasonic bonding process,thereby effectively reduce the difference between the chips.(4)Two kinds of jigs were used to bond the chip respectively.The concept of LWR(line width roughness)was introduced to measure the bonding line of two groups of chips.The bonding strength,sealing ability and pressure bearing strength of the chip were measured respectively.The results showed that compared with the jig without leveling function,the self-balancing jig can effectively reduce the LWR and improved the quality of the bonding line.Meanwhile,the self-balancing jig can enhance bonding strength 15.3%-45.1%,improve the bearing strength about 18.75%,flowing stability without leakage. |
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