Mechanical Neutral Plane Modulation in Polymer Flexible Multilayer Substrate for Ultrastable Sensor Fabrication

The development of a multilayer structure with an intermediate low-modulus material provides an added advantage to a flexible substrate. The intermediate layer restricts the interaction between the high-modulus layers by generating transverse shear strain across its thickness. Computational and experimental analyses have been performed in this regard. Here a tri-layer substrate is considered with polydimethylsiloxane (PDMS) as intermediate low-modulus material and polyethylene terephthalate (PET) as outer high-modulus material. Computational modeling shows that the proposed design facilitates a 44.89% and 25.51% reduction in the magnitude of developed surface strain, respectively when compared to the substrate without an intermediate PDMS layer and conventional tri-layer structure with a uniform middle layer (PDMS), respectively. A temperature sensor patch with PEDOT:PSS is fabricated on the designed substrate and its change in base resistance and sensitivity are observed with cyclic bending deformation. With the use of the proposed design, the change in base resistance is 8.6% after 300 bending cycles (with a radius of curvature
${R} = {1}$
cm). This value is considerably less when compared to the other two structures, i.e., 52.19% for the substrate without an intermediate PDMS layer and 27.7% for the conventional tri-layer structure with PDMS as a middle layer having a uniform thickness.