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New device architectures favorable for interaction with the soft and dynamic biological tissue are critical for the design of indwelling biosensors and neural interfaces. For the long-term use of such devices within the body, it is also critical that the component materials resist the physiological harsh mechanical and chemical conditions. Here, we describe the design and fabrication of mechanically and chemically robust 3D implantable electronics. This is achieved by using traditional photolithography to pattern electronics on liquid crystal elastomers (LCEs), a class of shape programmable materials. The chemical durability of LCE is evaluated under accelerated in vitro conditions simulating the physiological environment; for example, LCE exhibits less than 1% mass change under a hydrolytic medium simulating >1 year in vivo . By employing twisted nematic LCEs as dynamic substrates, we demonstrate electronics that are fabricated on planar substrates but upon release morph into programmed 3D shapes. These shapes are designed to enable intrinsically low failure strain materials to be extrinsically stretchable. For example, helical multichannel cables for electrode arrays withstand cyclic stretching and buckling over 10 000 cycles at 60% strain while being soaked in phosphate-buffered saline. We envision that these LCE-based electronics can be used for applications in implantable neural interfaces and biosensors. 

Polymer-based biomedical electronics provide a tunable platform to interact with nervous tissue both in vitro and in vivo. Ultimately, the ability to control functional properties of neural interfaces may provide important advantages to study the nervous system or to restore function in patients with neurodegenerative disorders. Liquid crystal elastomers (LCEs) are a class of smart materials that reversibly change shape when exposed to a variety of stimuli. Our interest in LCEs is based on leveraging this shape change to deploy electrode sites beyond the tissue regions exhibiting inflammation associated with chronic implantation. As a first step, we demonstrate that LCEs are cellular compatible materials that can be used as substrates for fabricating microelectrode arrays (MEAs) capable of recording single unit activity in vitro. Extracts from LCEs are non-cytotoxic (>70% normalized percent viability), as determined in accordance to ISO protocol 10993-5 using fibroblasts and primary murine cortical neurons. LCEs are also not functionally neurotoxic as determined by exposing cortical neurons cultured on conventional microelectrode arrays to LCE extract for 48 h. Microelectrode arrays fabricated on LCEs are stable, as determined by electrochemical impedance spectroscopy. Examination of the impedance and phase at 1 kHz, a frequency associated with single unit recording, showed results well within range of electrophysiological recordings over 30 days of monitoring in phosphate-buffered saline (PBS). Moreover, the LCE arrays are shown to support viable cortical neuronal cultures over 27 days in vitro and to enable recording of prominent extracellular biopotentials comparable to those achieved with conventional commercially-available microelectrode arrays.