Liquid crystal elastomers as substrates for 3D, robust, implantable electronics

Abstract

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 41 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. Fig. 3 (a) Schematic illustration of LCE spin-coating process. (b) Thickness of spin-coated LCE films as functions of LCE concentration and rotation speed (mean AE SD, n = 3). Polarized optical micrographs of spin-coated LCE (c) on a gold trace (viewed in reflection mode) and (d) on a twisted nematic LCE substrate (viewed in transmission mode). (Scale bars = 30 mm.)

Biomedical Microtechnologies Beyond Scholarly Impact

“…Research in microelectronics has led to the development of microchips with increased computational capacity and better energy efficiency, which will power future implantable devices [29,30]. New engineering strategies are being studied to develop adequate packaging techniques for bioelectronic implants using for instance high barrier performance materials [31] or complex architectures [32]. Advances in organic electronics will supply medical devices with better performing biointerfacing materials for charge transduction in sensing and stimulation applications [33][34][35][36][37].…”

Liquid Crystalline Polymers: Opportunities to Shape Neural Interfaces

“…For example, after monitoring the mass change of LCEs and two amorphous counterparts over 24 days in an oxidative medium, the LCE sample changed by only 9.48% while the amorphous counterparts lost physical integrity. The inherent hydrophobicity and liquid crystalline order enabled the polymer network to perform better than their amorphous counterparts that were much more susceptible to chemical attack and premature hydrolytic and oxidative degradation (44). The distinctive physical and chemical properties stemming from the LC order, such as its hydrophobicity and programmability, makes LCEs extremely desirable for a range of biomedical applications like soft robotics (45), actuators (46), artificial muscles (47,48), and antennas.…”

“…The challenges associated with transitioning from a material to a multi-layer device that leverages the advantages of a material are not trivial (44,57). The materials used in the device need to have enough interlayer adhesion to prevent early failure during chronic applications.…”

A Review on Materials and Technologies for Organic Large‐Area Electronics

“…Maeng and co‐workers used photolithography to pattern conductive pathways on liquid crystal elastomers (LCE). [ 277 ] The LCE substrate was prepared between two glass slides and its shape programmed resorting to photoalignment above the T g of the LCE. Then, researchers metal deposited thin‐film electronics over the LCE substrate, while it was still in a planar configuration and, upon release from the glass slide, the device transitioned into the envisioned programmed 3D shape.…”