Cryogenic Micromachining of Soft and Stretchable Polymer for Wearable Sensing Devices

A growing number of microchannel applications, particularly high-actuating wearable sensing devices, need novel fabrication techniques for acrylic-based soft polymer. Fabricating microchannel patterns on such soft polymers is highly challenging with the conventional lithography process due to their unpredictable mechanical response to deformation. Mechanical micro-milling process is a feasible method to fabricate various microchannel patterns. However, mechanical micro-milling has not yet been applied to soft polymers like VHB (Very high bond) acrylic elastomer. Due to low elasticity and high adhesion, machining of VHB is nearly impossible at room temperature. In order to machine a microchannel, mechanical micro-milling is proposed in combination with the cryogenic cooling process to cut the VHB around glass transition temperature because of its remarkable change of property from rubbery to glassy state. In this study, cryogenic micro-milling experimental setup is fabricated based on glass transition characteristics of VHB. Fixed machining parameters are then used to evaluate the effectiveness of micro-milling of VHB at room and cryogenic temperature. The result of the cutting test shows that the microchannel can be fabricated in VHB by the proposed cryogenic machining technique. In this context, cutting force and channel microstructure were also analysed at different machining conditions.