1,159 research outputs found
Implantable parylene-based wireless intraocular pressure sensor
This paper presents a novel implantable, wireless,
passive pressure sensor for ophthalmic applications. Two
sensor designs incorporating surface-micromachined
variable capacitor and variable capacitor/inductor are
implemented to realize the pressure sensitive components.
The sensor is monolithically microfabricated using parylene
as a biocompatible structural material in a suitable form
factor for increased ease of intraocular implantation.
Pressure responses of the microsensor are characterized
on-chip to demonstrate its high pressure sensitivity (> 7000
ppm/mmHg) with mmHg level resolution. An in vivo animal
study verifies the biostability of the sensor implant in the
intraocular environment after more than 150 days. This
sensor will ultimately be implanted at the pars plana or iris of
the eye to fulfill continuous intraocular pressure (IOP)
monitoring in glaucoma patients
Wireless Intraocular Pressure Sensing Using Microfabricated Minimally Invasive Flexible-Coiled LC Sensor Implant
This paper presents an implant-based wireless pressure
sensing paradigm for long-range continuous intraocular
pressure (IOP) monitoring of glaucoma patients. An implantable
parylene-based pressure sensor has been developed, featuring an
electrical LC-tank resonant circuit for passive wireless sensing
without power consumption on the implanted site. The sensor
is microfabricated with the use of parylene C (poly-chlorop-
xylylene) to create a flexible coil substrate that can be folded
for smaller physical form factor so as to achieve minimally invasive
implantation, while stretched back without damage for
enhanced inductive sensorโreader coil coupling so as to achieve
strong sensing signal. A data-processed external readout method
has also been developed to support pressure measurements. By
incorporating the LC sensor and the readout method, wireless
pressure sensing with 1-mmHg resolution in longer than 2-cm distance
is successfully demonstrated. Other than extensive on-bench
characterization, device testing through six-month chronic in vivo
and acute ex vivo animal studies has verified the feasibility and
efficacy of the sensor implant in the surgical aspect, including
robust fixation and long-term biocompatibility in the intraocular
environment. With meeting specifications of practical wireless
pressure sensing and further reader development, this sensing
methodology is promising for continuous, convenient, direct, and
faithful IOP monitoring
Microfabricated Implantable Parylene-Based Wireless Passive Intraocular Pressure Sensors
This paper presents an implantable parylene-based wireless pressure sensor for biomedical pressure sensing applications specifically designed for continuous intraocular pressure (IOP) monitoring in glaucoma patients. It has an electrical LC tank resonant circuit formed by an integrated capacitor and an inductor coil to facilitate passive wireless sensing using an external interrogating coil connected to a readout unit. Two surface-micromachined sensor designs incorporating variable capacitor and variable capacitor/inductor resonant circuits have been implemented to realize the pressure-sensitive components. The sensor is monolithically microfabricated by exploiting parylene as a biocompatible structural material in a suitable form factor for minimally invasive intraocular implantation. Pressure responses of the microsensor have been characterized to demonstrate its high pressure sensitivity (> 7000 ppm/mmHg) in both sensor designs, which confirms the feasibility of pressure sensing with smaller than 1 mmHg of resolution for practical biomedical applications. A six-month animal study verifies the in vivo bioefficacy and biostability of the implant in the intraocular environment with no surgical or postoperative complications. Preliminary ex vivo experimental results verify the IOP sensing feasibility of such device. This sensor will ultimately be implanted at the pars plana or on the iris of the eye to fulfill continuous, convenient, direct, and faithful IOP monitoring
Healthy aims: developing new medical implants and diagnostic equipment
Healthy Aims is a โฌ23-million, four-year project, funded under the EUโs Information Society Technology Sixth Framework program to develop intelligent medical implants and diagnostic systems (www.healthyaims.org). The project has 25 partners from 10 countries, including commercial,
clinical, and research groups. This consortium represents a combination of disciplines to design and fabricate new medical devices and components as well as to test them in laboratories and subsequent clinical trials.
The project focuses on medical implants for nerve stimulation and diagnostic equipment based on straingauge
technology
Design and fabrication of a low cost implantable bladder pressure monitor
In the frame of the Flemish Community funded project Bioflex we developed and fabricated an implant for short term (< 7 days) bladder pressure monitoring, and diagnosis of incontinence. This implant is soft and flexible to prevent damaging the bladder's inner wall. It contains a standard flexible electronic circuit connected to a battery, which are embedded in surface treated silicone to enhance the biocompatibility and prevent salt deposition. This article describes the fabrication of the pill and the results of preliminary cytotoxicity tests. The electronic design and its tests, implantation and the result of the in-vivo experimentation will be presented in other articles
Future of smart cardiovascular implants
Cardiovascular disease remains the leading cause of death in Western society. Recent technological advances have opened the opportunity of developing new and innovative smart stent devices that have advanced electrical properties that can improve diagnosis and even treatment of previously intractable conditions, such as central line access failure, atherosclerosis and reporting on vascular grafts for renal dialysis. Here we review the latest advances in the field of cardiovascular medical implants, providing a broad overview of the application of their use in the context of cardiovascular disease rather than an in-depth analysis of the current state of the art. We cover their powering, communication and the challenges faced in their fabrication. We focus specifically on those devices required to maintain vascular access such as ones used to treat arterial disease, a major source of heart attacks and strokes. We look forward to advances in these technologies in the future and their implementation to improve the human condition
Generalized Parity-Time Symmetry Condition for Enhanced Sensor Telemetry
Wireless sensors based on micro-machined tunable resonators are important in
a variety of applications, ranging from medical diagnosis to industrial and
environmental monitoring.The sensitivity of these devices is, however, often
limited by their low quality (Q) factor.Here, we introduce the concept of
isospectral party time reciprocal scaling (PTX) symmetry and show that it can
be used to build a new family of radiofrequency wireless microsensors
exhibiting ultrasensitive responses and ultrahigh resolution, which are well
beyond the limitations of conventional passive sensors. We show theoretically,
and demonstrate experimentally using microelectromechanical based wireless
pressure sensors, that PTXsymmetric electronic systems share the same
eigenfrequencies as their parity time (PT)-symmetric counterparts, but
crucially have different circuit profiles and eigenmodes. This simplifies the
electronic circuit design and enables further enhancements to the extrinsic Q
factor of the sensors
์ํ๋๋ฌผ์ ๋์ ๊ฒฝ ์๊ทน์ ์ํ ์์ ์ด์ํ ์ ๊ฒฝ์๊ทน๊ธฐ
ํ์๋
ผ๋ฌธ(๋ฐ์ฌ)--์์ธ๋ํ๊ต ๋ํ์ :๊ณต๊ณผ๋ํ ์ ๊ธฐยท์ ๋ณด๊ณตํ๋ถ,2020. 2. ๊น์ฑ์ค.In this study, a fully implantable neural stimulator that is designed to stimulate the brain in the small animal is described. Electrical stimulation of the small animal is applicable to pre-clinical study, and behavior study for neuroscience research, etc. Especially, behavior study of the freely moving animal is useful to observe the modulation of sensory and motor functions by the stimulation. It involves conditioning animal's movement response through directional neural stimulation on the region of interest. The main technique that enables such applications is the development of an implantable neural stimulator. Implantable neural stimulator is used to modulate the behavior of the animal, while it ensures the free movement of the animals. Therefore, stable operation in vivo and device size are important issues in the design of implantable neural stimulators. Conventional neural stimulators for brain stimulation of small animal are comprised of electrodes implanted in the brain and a pulse generation circuit mounted on the back of the animal. The electrical stimulation generated from the circuit is conveyed to the target region by the electrodes wire-connected with the circuit. The devices are powered by a large battery, and controlled by a microcontroller unit. While it represents a simple approach, it is subject to various potential risks including short operation time, infection at the wound, mechanical failure of the device, and animals being hindered to move naturally, etc. A neural stimulator that is miniaturized, fully implantable, low-powered, and capable of wireless communication is required.
In this dissertation, a fully implantable stimulator with remote controllability, compact size, and minimal power consumption is suggested for freely moving animal application. The stimulator consists of modular units of surface-type and depth-type arrays for accessing target brain area, package for accommodating the stimulating electronics all of which are assembled after independent fabrication and implantation using customized flat cables and connectors. The electronics in the package contains ZigBee telemetry for low-power wireless communication, inductive link for recharging lithium battery, and an ASIC that generates biphasic pulse for neural stimulation. A dual-mode power-saving scheme with a duty cycling was applied to minimize the power consumption. All modules were packaged using liquid crystal polymer (LCP) to avoid any chemical reaction after implantation.
To evaluate the fabricated stimulator, wireless operation test was conducted. Signal-to-Noise Ratio (SNR) of the ZigBee telemetry were measured, and its communication range and data streaming capacity were tested. The amount of power delivered during the charging session depending on the coil distance was measured. After the evaluation of the device functionality, the stimulator was implanted into rats to train the animals to turn to the left (or right) following a directional cue applied to the barrel cortex. Functionality of the device was also demonstrated in a three-dimensional maze structure, by guiding the rats to navigate better in the maze. Finally, several aspects of the fabricated device were discussed further.๋ณธ ์ฐ๊ตฌ์์๋ ์ํ ๋๋ฌผ์ ๋๋๋ฅผ ์๊ทนํ๊ธฐ ์ํ ์์ ์ด์ํ ์ ๊ฒฝ์๊ทน๊ธฐ๊ฐ ๊ฐ๋ฐ๋์๋ค. ์ํ ๋๋ฌผ์ ์ ๊ธฐ์๊ทน์ ์ ์์ ์ฐ๊ตฌ, ์ ๊ฒฝ๊ณผํ ์ฐ๊ตฌ๋ฅผ ์ํ ํ๋์ฐ๊ตฌ ๋ฑ์ ํ์ฉ๋๋ค. ํนํ, ์์ ๋กญ๊ฒ ์์ง์ด๋ ๋๋ฌผ์ ๋์์ผ๋ก ํ ํ๋ ์ฐ๊ตฌ๋ ์๊ทน์ ์ํ ๊ฐ๊ฐ ๋ฐ ์ด๋ ๊ธฐ๋ฅ์ ์กฐ์ ์ ๊ด์ฐฐํ๋ ๋ฐ ์ ์ฉํ๊ฒ ํ์ฉ๋๋ค. ํ๋ ์ฐ๊ตฌ๋ ๋๋์ ํน์ ๊ด์ฌ ์์ญ์ ์ง์ ์ ์ผ๋ก ์๊ทนํ์ฌ ๋๋ฌผ์ ํ๋๋ฐ์์ ์กฐ๊ฑดํํ๋ ๋ฐฉ์์ผ๋ก ์ํ๋๋ค. ์ด๋ฌํ ์ ์ฉ์ ๊ฐ๋ฅ์ผ ํ๋ ํต์ฌ๊ธฐ์ ์ ์ด์ํ ์ ๊ฒฝ์๊ทน๊ธฐ์ ๊ฐ๋ฐ์ด๋ค. ์ด์ํ ์ ๊ฒฝ์๊ทน๊ธฐ๋ ๋๋ฌผ์ ์์ง์์ ๋ฐฉํดํ์ง ์์ผ๋ฉด์๋ ๊ทธ ํ๋์ ์กฐ์ ํ๊ธฐ ์ํด ์ฌ์ฉ๋๋ค. ๋ฐ๋ผ์ ๋๋ฌผ ๋ด์์์ ์์ ์ ์ธ ๋์๊ณผ ์ฅ์น์ ํฌ๊ธฐ๊ฐ ์ด์ํ ์ ๊ฒฝ์๊ทน๊ธฐ๋ฅผ ์ค๊ณํจ์ ์์ด ์ค์ํ ๋ฌธ์ ์ด๋ค. ๊ธฐ์กด์ ์ ๊ฒฝ์๊ทน๊ธฐ๋ ๋๋์ ์ด์๋๋ ์ ๊ทน ๋ถ๋ถ๊ณผ, ๋๋ฌผ์ ๋ฑ ๋ถ๋ถ์ ์์นํ ํ๋ก๋ถ๋ถ์ผ๋ก ๊ตฌ์ฑ๋๋ค. ํ๋ก์์ ์์ฐ๋ ์ ๊ธฐ์๊ทน์ ํ๋ก์ ์ ์ ์ผ๋ก ์ฐ๊ฒฐ๋ ์ ๊ทน์ ํตํด ๋ชฉํ ์ง์ ์ผ๋ก ์ ๋ฌ๋๋ค. ์ฅ์น๋ ๋ฐฐํฐ๋ฆฌ์ ์ํด ๊ตฌ๋๋๋ฉฐ, ๋ด์ฅ๋ ๋ง์ดํฌ๋ก ์ปจํธ๋กค๋ฌ์ ์ํด ์ ์ด๋๋ค. ์ด๋ ์ฝ๊ณ ๊ฐ๋จํ ์ ๊ทผ๋ฐฉ์์ด์ง๋ง, ์งง์ ๋์์๊ฐ, ์ด์๋ถ์์ ๊ฐ์ผ์ด๋ ์ฅ์น์ ๊ธฐ๊ณ์ ๊ฒฐํจ, ๊ทธ๋ฆฌ๊ณ ๋๋ฌผ์ ์์ฐ์ค๋ฌ์ด ์์ง์ ๋ฐฉํด ๋ฑ ์ฌ๋ฌ ๋ฌธ์ ์ ์ ์ผ๊ธฐํ ์ ์๋ค. ์ด๋ฌํ ๋ฌธ์ ์ ๊ฐ์ ์ ์ํด ๋ฌด์ ํต์ ์ด ๊ฐ๋ฅํ๊ณ , ์ ์ ๋ ฅ, ์ํํ๋ ์์ ์ด์ํ ์ ๊ฒฝ์๊ทน๊ธฐ์ ์ค๊ณ๊ฐ ํ์ํ๋ค.
๋ณธ ์ฐ๊ตฌ์์๋ ์์ ๋กญ๊ฒ ์์ง์ด๋ ๋๋ฌผ์ ์ ์ฉํ๊ธฐ ์ํ์ฌ ์๊ฒฉ ์ ์ด๊ฐ ๊ฐ๋ฅํ๋ฉฐ, ํฌ๊ธฐ๊ฐ ์๊ณ , ์๋ชจ์ ๋ ฅ์ด ์ต์ํ๋ ์์ ์ด์ํ ์๊ทน๊ธฐ๋ฅผ ์ ์ํ๋ค. ์ค๊ณ๋ ์ ๊ฒฝ์๊ทน๊ธฐ๋ ๋ชฉํ๋ก ํ๋ ๋๋ ์์ญ์ ์ ๊ทผํ ์ ์๋ ํ๋ฉดํ ์ ๊ทน๊ณผ ํ์นจํ ์ ๊ทน, ๊ทธ๋ฆฌ๊ณ ์๊ทน ํ์ค ์์ฑ ํ๋ก๋ฅผ ํฌํจํ๋ ํจํค์ง ๋ฑ์ ๋ชจ๋๋ค๋ก ๊ตฌ์ฑ๋๋ฉฐ, ๊ฐ๊ฐ์ ๋ชจ๋์ ๋
๋ฆฝ์ ์ผ๋ก ์ ์๋์ด ๋๋ฌผ์ ์ด์๋ ๋ค ์ผ์ด๋ธ๊ณผ ์ปค๋ฅํฐ๋ก ์ฐ๊ฒฐ๋๋ค. ํจํค์ง ๋ด๋ถ์ ํ๋ก๋ ์ ์ ๋ ฅ ๋ฌด์ ํต์ ์ ์ํ ์ง๊ทธ๋น ํธ๋์๋ฒ, ๋ฆฌํฌ ๋ฐฐํฐ๋ฆฌ์ ์ฌ์ถฉ์ ์ ์ํ ์ธ๋ํฐ๋ธ ๋งํฌ, ๊ทธ๋ฆฌ๊ณ ์ ๊ฒฝ์๊ทน์ ์ํ ์ด์์ฑ ์๊ทนํํ์ ์์ฑํ๋ ASIC์ผ๋ก ๊ตฌ์ฑ๋๋ค. ์ ๋ ฅ ์ ๊ฐ์ ์ํด ๋ ๊ฐ์ ๋ชจ๋๋ฅผ ํตํด ์ฌ์ฉ๋ฅ ์ ์กฐ์ ํ๋ ๋ฐฉ์์ด ์ฅ์น์ ์ ์ฉ๋๋ค. ๋ชจ๋ ๋ชจ๋๋ค์ ์ด์ ํ์ ์๋ฌผํ์ , ํํ์ ์์ ์ฑ์ ์ํด ์ก์ ํด๋ฆฌ๋จธ๋ก ํจํค์ง๋์๋ค. ์ ์๋ ์ ๊ฒฝ์๊ทน๊ธฐ๋ฅผ ํ๊ฐํ๊ธฐ ์ํด ๋ฌด์ ๋์ ํ
์คํธ๊ฐ ์ํ๋์๋ค. ์ง๊ทธ๋น ํต์ ์ ์ ํธ ๋ ์ก์๋น๊ฐ ์ธก์ ๋์์ผ๋ฉฐ, ํด๋น ํต์ ์ ๋์๊ฑฐ๋ฆฌ ๋ฐ ๋ฐ์ดํฐ ์คํธ๋ฆฌ๋ฐ ์ฑ๋ฅ์ด ๊ฒ์ฌ๋์๊ณ , ์ฅ์น์ ์ถฉ์ ์ด ์ํ๋ ๋ ์ฝ์ผ๊ฐ์ ๊ฑฐ๋ฆฌ์ ๋ฐ๋ผ ์ ์ก๋๋ ์ ๋ ฅ์ ํฌ๊ธฐ๊ฐ ์ธก์ ๋์๋ค. ์ฅ์น์ ํ๊ฐ ์ดํ, ์ ๊ฒฝ์๊ทน๊ธฐ๋ ์ฅ์ ์ด์๋์์ผ๋ฉฐ, ํด๋น ๋๋ฌผ์ ์ด์๋ ์ฅ์น๋ฅผ ์ด์ฉํด ๋ฐฉํฅ ์ ํธ์ ๋ฐ๋ผ ์ข์ฐ๋ก ์ด๋ํ๋๋ก ํ๋ จ๋์๋ค. ๋ํ, 3์ฐจ์ ๋ฏธ๋ก ๊ตฌ์กฐ์์ ์ฅ์ ์ด๋๋ฐฉํฅ์ ์ ๋ํ๋ ์คํ์ ํตํ์ฌ ์ฅ์น์ ๊ธฐ๋ฅ์ฑ์ ์ถ๊ฐ์ ์ผ๋ก ๊ฒ์ฆํ์๋ค. ๋ง์ง๋ง์ผ๋ก, ์ ์๋ ์ฅ์น์ ํน์ง์ด ์ฌ๋ฌ ์ธก๋ฉด์์ ์ฌ์ธต์ ์ผ๋ก ๋
ผ์๋์๋ค.Chapter 1 : Introduction 1
1.1. Neural Interface 2
1.1.1. Concept 2
1.1.2. Major Approaches 3
1.2. Neural Stimulator for Animal Brain Stimulation 5
1.2.1. Concept 5
1.2.2. Neural Stimulator for Freely Moving Small Animal 7
1.3. Suggested Approaches 8
1.3.1. Wireless Communication 8
1.3.2. Power Management 9
1.3.2.1. Wireless Power Transmission 10
1.3.2.2. Energy Harvesting 11
1.3.3. Full implantation 14
1.3.3.1. Polymer Packaging 14
1.3.3.2. Modular Configuration 16
1.4. Objectives of This Dissertation 16
Chapter 2 : Methods 18
2.1. Overview 19
2.1.1. Circuit Description 20
2.1.1.1. Pulse Generator ASIC 21
2.1.1.2. ZigBee Transceiver 23
2.1.1.3. Inductive Link 24
2.1.1.4. Energy Harvester 25
2.1.1.5. Surrounding Circuitries 26
2.1.2. Software Description 27
2.2. Antenna Design 29
2.2.1. RF Antenna 30
2.2.1.1. Design of Monopole Antenna 31
2.2.1.2. FEM Simulation 31
2.2.2. Inductive Link 36
2.2.2.1. Design of Coil Antenna 36
2.2.2.2. FEM Simulation 38
2.3. Device Fabrication 41
2.3.1. Circuit Assembly 41
2.3.2. Packaging 42
2.3.3. Electrode, Feedthrough, Cable, and Connector 43
2.4. Evaluations 45
2.4.1. Wireless Operation Test 46
2.4.1.1. Signal-to-Noise Ratio (SNR) Measurement 46
2.4.1.2. Communication Range Test 47
2.4.1.3. Device Operation Monitoring Test 48
2.4.2. Wireless Power Transmission 49
2.4.3. Electrochemical Measurements In Vitro 50
2.4.4. Animal Testing In Vivo 52
Chapter 3 : Results 57
3.1. Fabricated System 58
3.2. Wireless Operation Test 59
3.2.1. Signal-to-Noise Ratio Measurement 59
3.2.2. Communication Range Test 61
3.2.3. Device Operation Monitoring Test 62
3.3. Wireless Power Transmission 64
3.4. Electrochemical Measurements In Vitro 65
3.5. Animal Testing In Vivo 67
Chapter 4 : Discussion 73
4.1. Comparison with Conventional Devices 74
4.2. Safety of Device Operation 76
4.2.1. Safe Electrical Stimulation 76
4.2.2. Safe Wireless Power Transmission 80
4.3. Potential Applications 84
4.4. Opportunities for Further Improvements 86
4.4.1. Weight and Size 86
4.4.2. Long-Term Reliability 93
Chapter 5 : Conclusion 96
Reference 98
Appendix - Liquid Crystal Polymer (LCP) -Based Spinal Cord Stimulator 107
๊ตญ๋ฌธ ์ด๋ก 138
๊ฐ์ฌ์ ๊ธ 140Docto
Biotelemetric Wireless Intracranial Pressure Monitoring: An In Vitro
Assessment of intracranial pressure (ICP) is of great importance in management of traumatic brain injuries (TBIs). The existing clinically established ICP measurement methods require catheter insertion in the cranial cavity. This increases the risk of infection and hemorrhage. Thus, noninvasive but accurate techniques are attractive. In this paper, we present two wireless, batteryless, and minimally invasive implantable sensors for continuous ICP monitoring. The implants comprise ultrathin (50โฮผm) flexible spiral coils connected in parallel to a capacitive microelectromechanical systems (MEMS) pressure sensor. The implantable sensors are inductively coupled to an external on-body reader antenna. The ICP variation can be detected wirelessly through measuring the reader antennaโs input impedance. This paper also proposes novel implant placement to improve the efficiency of the inductive link. In this study, the performance of the proposed telemetry system was evaluated in a hydrostatic pressure measurement setup. The impact of the human tissues on the inductive link was simulated using a 5โmm layer of pig skin. The results from the in vitro measurement proved the capability of our developed sensors to detect ICP variations ranging from 0 to 70โmmHg at 2.5โmmHg intervals
Extending the limits of wireless power transfer to miniaturized implantable electronic devices
Implantable electronic devices have been evolving at an astonishing pace, due to the development of fabrication techniques and consequent miniaturization, and a higher efficiency of sensors, actuators, processors and packaging. Implantable devices, with sensing, communication, actuation, and wireless power are of high demand, as they pave the way for new applications and therapies. Long-term and reliable powering of such devices has been a challenge since they were first introduced. This paper presents a review of representative state of the art implantable electronic devices, with wireless power capabilities, ranging from inductive coupling to ultrasounds. The different power transmission mechanisms are compared, to show that, without new methodologies, the power that can be safely transmitted to an implant is reaching its limit. Consequently, a new approach, capable of multiplying the available power inside a brain phantom for the same specific absorption rate (SAR) value, is proposed. In this paper, a setup was implemented to quadruple the power available in the implant, without breaking the SAR limits. A brain phantom was used for concept verification, with both simulation and measurement data.This work is supported by FCT with the reference project PTDC/EEI-TEL/5250/2014, by FEDER funds through Projecto 3599-Promover a Produรงรฃo Cientรญfica e Desenvolvimento Tecnolรณgico e a Constituiรงรฃo de Redes Temรกticas (3599-PPCDT) and by grant SFRH/BD/116554/2016.info:eu-repo/semantics/publishedVersio
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