別紙41 (課程博士(英文))Date of submission (mon伽 day, year)

January lolh,2020

DepanmenlElectricaland Electronic

Stud引111D Number

D133275
TakeshiKawano

Information En部neerin宮Supervisors

IshikawaYasuhiko
PP11Ca"1"s name

Yusuke Morikawa

Abstmct (Docto"
Ti11e ofThesis

Stretchable Kil'igami devices for bi010gical applications

Approx.80o words
Techn010牙ies of recording bi010gical signals from brain,1)eart, and muscle are expected to be
Used for the treatment of psychiatric and neur010gical disorders. These tecl)n010gies can also
be used for Testoring lost functions, such as brain‑machine interface and hun〕an‑machineinterface.

Microscale needle"electrodes and film electrodes are commonly used for the recordin曾 ofbi010曾ical signals from tissues.1ntimate inte曾ration between electrical devices and softbi010gicaltissues can be achieved while device materialis biocompatibility and the mat田・ial'Sn)echanical characteristics (e.g. Youn牙's modulus) are similar to those of the bi010曾ical
tlssues.

To this purpose, numerous types of aexible and stretchable devices have beendeveloped. conventional aexible devices are fabricated using a polymeric material, however
the Young's lnodulus is approxin〕ately six orders of magnitude hi今her than tl)ose of thebi010gical tissues (e.曾. brain and muscle).1n addition, Youn宮's moduli of elastomer materials
Used in S訂'etchable devices are large con〕pared to those of the bi010gical tissues. Therefore,
there is a possibility that these mismatches may induce tissue dan〕a又e and malfunction.
Moreover, the mismatch of Young's modulus between soft elastomer materials and ri宮iddevice con)ponents (e.g. transistors and interconnections) may be the cause of failure of thedevlce components, due to the lar牙e S訂'ain applied to the S訂'etchable device.
In this study, a low invasive neuralinterface device usin曾 a Kirigami structure is
Proposed for bi010gical applications. The aim is to achieve an intimate inte宮ration between
electrical devices and soft bi010gicaltissues. A remarkable feature of the Kiri牙ami structure
is its h喰h stretchabi1北y, which includes a high strain ratio and low effective modulus
Moreover, the mechanical characteristics of the KⅡ'i牙ami structure can be designed (e.客. slit
Iength and gap of the lくiri曾an〕i S訂'ucture).1n contrast, characteristics of conventional
Stretchable devices depend on the intrinsic characteYistics of the mat田,ials used.

The stretcl)ability and recording capability of the Kirigami device has been confirmed
as a Kiri曾amibioprobe device、 A displacement n)odelofthe Kirigamistructure was derived toestimate the deformation of the Kh'igami structuYe, which depends on the applied force (orS仇'ess).1n addition, the Sれ'ess diS仇'ibution in a Kh'igami structuTe was calculated. The
displacement model and the stress distribution results pTovide an effective and robust
method of designing a Kirigan〕i device. A Kiri曾ami device was designed and fabricated for theapplications to electrocortic0容ram (ECOG) and electrocaTdi0曾ranl (ECG) signal recordin宮Sfrom mice. The fabrication process was based on parylene、microelectYon)echanical systems(MEMS), which includes embedded platin11m layer playin曾 roles in microelectrode and device
interconnection. The fabricated Kirigami bioprobe device exhibited the stabi1辻y of itselectrical impedance with the device stretching, and the mechanical charact田.istics
Colnparable to the soft bi010曾ical tissues was confirmed.1n addition, the durability of the1くirigami device was confirmed during a 4,000、cycle strain test. The recording capability of
the fabricated Kirigami device was confirmed in the ECOG and ECG signal recordings using

mice. These experiments indicated the ability of the Kiri套ami device to achieve the intimate
inte牙ration with bi010曾ical tissues. However, the fabricated Kirigami device caused
displacement on the bi010曾icaltissues, which show their lar牙e deformation
To achieve the device's stability on deformable bi010gical, such as heart and muscle, adonut・shaped Kiri宮ami device was proposed. The donut'shaped Kirigami device exhibited theStability on the deformable tissue surface, as confirmed in the displacement test usin宮deformable ba110on instead of real bi010号ical tissues. The displacement test results exhibit
five‑to‑eight times less displacement, compared to the displacement caused by the other
Sheet・type Kirigami device which were used in ECOG and ECG applications. The recordin套Capability and stability ofthe fabricated donut'shaped Kiri曾ami device were also confirmed inthe bi010gical si牙nal recordin牙S from lar今e deformable tissues, includin曾 heart and hind limb
Of lnice

Another cha11en曾e faced by the Kirigami device was the smooth inte曾ration of 北S rigid
Components in the stretchable Kirigami structures, in order to achieve the device'Smultifunctionality. An optoelectrical Kiri曾ami device was proposed for the treatment ofheartdisease. The proposed device includes arrays of li曾ht emitting diodes (LED) for optical
Stimulation to and microelectrodes for ECG signal recordin宮 from the li曾ht'sensitive proteins
expressed heart of a mouse. Regarding characterizations of the optoelectrical Kiri曾ami
device, no si宮nificant chan牙es in resistance of the device interconnections durin牙 theKiri号ami stretching. Moreover, there was no chan牙e in the resistance during the durability
test for 300‑40o cycles.1t was also confirmed that the latch structures showed hi今h enoughfixation force to enable the device's fixation on the heart tissue. The LED functionality test

revealed a yield of loo%. These results successfU11y demonstrated a highly stretchable device
Suitable for cardiac tissue defibri11ation usin宮 Optogenetic stimulation

In summary, these results indicate the capability of the Kiri晉ami device as theappropriate platform of low invasive neuralinterface devices.1t is believed that the features
Of the Kiri目ami device can be extended to applications involvin牙 the integration of electrical
Components with bi010gicaltissues. Moreover, the high stretchability, stability, and uniquetransformation of the Kiri牙ami structure wi11 expand possibilities for stretchable electronicsincludin曾 Sensors and actuators.