Thermal Release Transfer Printing for Stretchable Conformal Bioelectronics

Abstract

Soft neural electrode arrays that are mechanically matched between neural tissues and electrodes offer valuable opportunities for the development of disease diagnose and brain computer interface systems. Here, a thermal release transfer printing method for fabrication of stretchable bioelectronics, such as soft neural electrode arrays, is presented. Due to the large, switchable and irreversible change in adhesion strength of thermal release tape, a low‐cost, easy‐to‐operate, and temperature‐controlled transfer printing process can be achieved. The mechanism of this method is analyzed by experiments and fracture‐mechanics models. Using the thermal release transfer printing method, a stretchable neural electrode array is fabricated by a sacrificial‐layer‐free process. The ability of the as‐fabricated electrode array to conform different curvilinear surfaces is confirmed by experimental and theoretical studies. High‐quality electrocorticography signals of anesthetized rat are collected with the as‐fabricated electrode array, which proves good conformal interface between the electrodes and dura mater. The application of the as‐fabricated electrode array on detecting the steady‐state visual evoked potentials research is also demonstrated by in vivo experiments and the results are compared with those detected by stainless‐steel screw electrodes.

Transfer printing techniques for flexible and stretchable inorganic electronics

“…Another type of transfer printing technique involving surface chemistry with a much more simplified process is the tape transfer printing, where solvent releasable tapes 13,65,66 or thermal releasable tapes 10,67 are used as stamps. Figures 3b-1 66 shows the typical transfer printing process based on a commercially available solvent releasable adhesive tape to retrieve and print devices with high yields.…”

“…The last decade has witnessed the fast progresses and great achievements of flexible and stretchable inorganic electronics, which removes the planar, rigid, and brittle design constraints associated with conventional electronics via the integration of hard inorganic semiconductor materials in delicate structural layouts with flexible substrates. [1][2][3][4][5] This technology has enabled many novel applications that are impossible for conventional electronics, such as curvilinear electronics, [6][7][8] bio-integrated electronics, [9][10][11] epidermal electronics, [12][13][14] transient electronics, [15][16][17][18] deformable opto-electronics, [19][20][21][22][23][24] and many others. [25][26][27] Figure 1 shows some examples of flexible and stretchable inorganic devices with performance equal to those fabricated by established conventional technologies using well-developed inorganic semiconductor and metal materials, but in foldable, stretchable and curvilinear format.…”

Flexible inorganic bioelectronics

“…Therefore, reducing the electrode's thickness becomes the first path towards intimate contact, low impedance and consequently better signals. [98][99][100][101][102][103][104] Compared with routine electrodes, flexible and large area devices based on polymer substrate, typically the polyimide (PI), are more attractive due to better contact as well as the ability to record signal in larger areas. 101 The flexible multichannel electrode array based on MEMS with total thickness of 10 μm and as many as 252 channels has been proved to be effective in ECoG recording by in vivo testing, even after as long as 4.5 month's implantation.…”

Recent Advances on Thermal Management of Flexible Inorganic Electronics

“…Due to the unique mechanical properties of FIEDs, they can have conformal contacts with biological tissues under complex deformations, which enable the real-time monitoring of human vital signs for early diagnosis [17]. In the past decade, researchers have demonstrated several flexible real-time health monitoring devices to measure human vital signs including body temperature [4,18], blood glucose [19][20][21], blood oxygen [22], skin hydration [3], blood flow [2], brain electrophysiological signal [23,24], electrocardiography (ECG) [25], etc.…”