FLOBIO

Prior work

A wirelessly powered implant on flexible fan-out packaging

FLOBIO's technology will build directly on a published demonstration of a near-field, wirelessly powered bio-implantable system assembled with fan-out wafer-level packaging on a biocompatible elastomer.

Source publication

A flexible, heterogeneously integrated wireless powered system for bio-implantable applications using fan-out wafer-level packaging

G. Ezhilarasu, A. Hanna, R. Irwin, A. Alam, S. S. Iyer — 2018 IEEE International Electron Devices Meeting (IEDM), University of California, Los Angeles.

> 15 %

wireless power transfer efficiency at 1 cm

~535 µm

total thickness of the implantable system

< 2 cm

device diameter

~5 mm

bending radius on a biocompatible elastomer

Figures

What the paper measured

FIG. 1

System concept

Schematic of a wirelessly powered implantable system built on a flexible substratea
Table of the components and their dimensions used in fabricationb
Circuit diagram of the wireless power transfer link and implantc
(a) Schematic of the system concept, (b) table of components used in fabrication and (c) circuit diagram of the system.
FIG. 2

Coil design

Table of optimized coil design parametersa
Inductance and quality factor versus frequency for the external coilb
Inductance and quality factor versus frequency for the implant coilc
(a) Optimized design parameters for the WPT coils. Inductance (µH) and quality factor versus frequency, simulated and measured, for (b) the external coil and (c) the implant coil.
FIG. 3

Power transfer efficiency

Efficiency versus frequency at different distances in aira
Efficiency versus frequency at different distances in PBSb
Efficiency versus distance in air and PBS comparedc
Efficiency versus bending radius in air and PBSd
PTE (power transfer efficiency, %) of the resonant WPT link versus frequency for different coupling distances in (a) air and (b) PBS, with (c) efficiency versus distance and (d) the effect of bending.
FIG. 4

Flexure & reliability

Inductance and quality factor versus number of bending cyclesa
PDMS surface strain versus normalized distanceb
Peak die strain versus inter-die spacing for several die thicknessesc
(a) Inductance (µH) and quality factor of two implant coils, samples A and B, as a function of cumulative bending cycles at 10 mm and 5 mm radii for up to 1000 cycles, together with (b) PDMS surface strain and (c) peak die strain in the flexible package.
FIG. 5

Fabrication flow

Plating of the first metal layer by a semi-additive process01
Patterning of the SU-8 corrugation and bridge structures02
Placement of silicon dies onto a release tape handler03
Dispensing of PDMS around the placed dies04
Compression molding of PDMS with a second handler wafer05
Thermal release of the initial handler wafer06
Deposition of the Parylene-C and SU-8 dielectric layers07
Via holes etched through the dielectric08
Semi-additive plating of the second metal layer09
Final passivation and release from the silicon handler10
Photograph of the released flexible implant glowing11
Process flow for fabrication of FlexTrate™: metal redistribution and corrugated SU-8 layers are built up, bare dies are placed on a release tape, overmolded in PDMS, released from the handler and finally encapsulated in Parylene-C and SU-8 before the finished flexible implant is released.
FIG. 6

Fabricated device

Annotated top-side optical image of the fabricated wireless power transfer systema
Bottom-side view through PDMS with zoomed images of the µLED, LDO and Schottky diodeb
(a) Optical image (top side) of the fabricated WPT system. (b) Optical image of the bottom side of the same sample viewed through the PDMS, with zoomed-in images of the green µLED, the LDO and the Schottky diode.
FIG. 7

Integrated system performance

Output voltage versus coupling distance in aira
Output voltage versus coupling distance in PBSb
Photographs of the flexible device operating at increasing bendc
Comparison of output voltage (V of the LDO, in volts) versus coupling distance for the breadboard test system and the integrated system on FlexTrate™ in (a) air and (b) PBS. (c) shows the flexible device operating at increasing bend.

Figures reproduced from the source publication, Ezhilarasu et al., IEEE IEDM 2018.

Method

How the device was built

  • 01

    Fan-out wafer-level packaging (FlexTrate™) embeds bare dies in a polydimethylsiloxane (PDMS) mold with fine-pitch copper redistribution interconnects.

  • 02

    Laser-assisted micro transfer printing places GaN µLEDs with the precision and yield needed for a fully flexible, inorganic optical source.

  • 03

    A near-field inductive link removes both the battery and the tethered power lead, so the implanted device has no external connection.

  • 04

    The work was carried out at UCLA's Center for Heterogeneous Integration and Performance Scaling and presented at IEEE IEDM 2018.

Building on this work

We will work with biopharma and clinical partners to turn this hardware into screening toolkits and co-developed bioelectronic therapies.