Direct Fabrication of Stretchable Electronics on a Polymer Substrate with Process‐Integrated Programmable Rigidity

Abstract

Despite the increasingly important role of stretchable electronics for use as the human–machine interface, their manufacturing in a commercially realistic manner remains an unresolved challenge. The bottleneck lies in the efficiency and scalability of transfer printing that is typically employed in the fabrication process to enable device stretchability via strain isolation. Here, the use of a polymer substrate with programmable rigidity for direct manufacturing of stretchable electronics is reported, forgoing the need for transfer printing while significantly enhancing strain isolation. The process starts with a stretchable elastomeric substrate synthesized via the thiol‐acrylate click chemistry. Designable rigid islands can be introduced via spatially confined oxidation of the elastomer. Strain‐sensitive microdevices can then be directly fabricated onto the rigid islands without transfer printing. Following this manufacturing scheme, a fast‐responding stretchable temperature sensor is demonstrated, with unusual accuracy and real‐time temperature monitoring capability suitable for use in a highly dynamic environment. Importantly, the critical fabrication step that introduces the programmable substrate rigidity is fully integrated into a well‐established lithographic process. Therefore, the methodology not only reduces greatly the complexity in fabricating prototype devices but also points to a highly effective way for potential manufacturing in a commercial setting.

Conformal Devices for Thermal Sensing and Heating in Biomedical and Human–Machine Interaction Applications

“…The conformality of the device enhanced SNR and provided higher heat transfer efficiency on the targeted object. The Archimedean spiral design can combine with strain‐insensitive technologies to further enhance the device stretchability . The small size of the device (12.6 mm 2 ) allows the monitoring of tissue temperature and localized thermogenesis.…”

Flexible inorganic bioelectronics

“…Especially in the biomedical field, electronic devices have to be flexible and/or stretchable in order to intimately integrate with the soft, deformable, and configuration-complicated biological tissue. [25][26][27][28][29][30] Flexibility of the electronic devices can be realized by reducing their thickness, since the bending stiffness decreases at a three orders faster speed with decreasing thickness, while stretchability can be achieved by pre-strain formed wavy configuration, island-bridge structure and serpentine and fractal interconnects design. 23,[31][32][33][34][35][36][37] The main idea in these strategies is to utilize the buckling/post buckling of the delicate patterned inorganic materials to minimize the strain in the functional layer while the whole devices are under large deformation.…”

“…58 The extrinsic elements that should be considered are the dynamic deformation of the human body as well as the environmental effects like temperature and light. 25,[59][60][61][62] Besides, the internal interfaces of devices as well as the human-device interfaces are also important in collecting the signal accurately in the long term. Micro-structure enhanced device internal interface and tattoo-like electrode enabled intimate contact are the inspiring solutions to these interfacial issues.…”

Recent Developments of Flexible and Stretchable Electrochemical Biosensors

“…The recent development in cost-effective fabrication approaches includes various additive manufacturing or printing technologies. Integrating electrochemical biosensors on soft substrates with these approaches renders flexible and stretchable properties for wearable applications ( Figure 1) [2,[29][30][31][32][33][34]. Printing electrochemical sensing materials directly onto soft textiles of daily clothes allows for timely monitoring of critical information, without compromising the level of comfort or function of the garment [35][36][37].…”