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The conventional method to evaluate spinous process angles (SPAs) is to obtain the spinous processes (SP) curve by manually locating spinous processes on radiographs. HR-Net is a deep neural network which uses a multi-feature fusion strategy for keypoints detection. The objectives of this study are to automatically locate the SP on the ultrasound (US) transverse images by applying the High-Resolution network (HR-Net) and then to measure the SPAs on the reconstructed coronal image. The HR-Net model was trained on 1200 US transverse images and tested on 386 images to locate the spinous process. Twenty-five scoliotic subjects were scanned for the evaluation of SPAs measurement. After detecting the SP positions on each frame using HR-Net, the 3D image volumes were reconstructed, and the SPAs were measured on the coronal planes. HR-Net predicted the five keypoints on the test set with the average accuracy of 74.09% with the SP accuracy of 80.05%. The mean absolute difference (MAD) of SPAs between US and radiographic measurement was 2. 7±2.0°, and the correlation was 0.89. The results showed that the HR-Net method could automatically locate the spinous processes on US transverse images and moreover provide accurate estimation of SPAs for scoliotic subjects.

Cell transplantation is a way of treatment in which lost cellular functions can be recovered by transplanted cells. However, hypoxic conditions on the transplanted site hinder the survival of the cells. This paper presents an oxygenation device for cell transplantations to improve the engraftment and transplanted cell survival. The flexible and thin polymeric hollow mesh working as gas capillaries can effectively transport oxygen between microvessels and transplanted cells, maintaining adequate oxygen tension for cell survival and functionality. Devices are designed, fabricated, and characterized in this study. Both in silico and in vivo models demonstrate a 4-5 fold increase in cell viability compared to the control group without oxygen-transporting mesh. The results showed that a broad spectrum of cell transplantations could benefit from such MEMS oxygen-transporting device.

The elimination of integrated batteries in biomedical implants holds great promise for improving health outcomes in patients with implantable devices. However, despite extensive research in wireless power transfer, achieving efficient power transfer and effective operational range have remained a hindering challenge within anatomical constraints. Objective : We hereby demonstrate an intravascular wireless and batteryless microscale stimulator, designed for (1) low power dissipation via intermittent transmission and (2) reduced fixation mechanical burden via deployment to the anterior cardiac vein (ACV, ∼3.8 mm in diameter). Methods : We introduced a unique coil design circumferentially confined to a 3 mm diameter hollow-cylinder that was driven by a novel transmitter-based control architecture with improved power efficiency. Results : We examined wireless capacity using heterogenous bovine tissue, demonstrating >5 V stimulation threshold with up to 20 mm transmitter-receiver displacement and 20° of misalignment. Feasibility for human use was validated using Finite Element Method (FEM) simulation of the cardiac cycle, guided by pacer phantom-integrated Magnetic Resonance Images (MRI). Conclusion : This system design thus enabled sufficient wireless power transfer in the face of extensive stimulator miniaturization. Significance : Our successful feasibility studies demonstrated the capacity for minimally invasive deployment and low-risk fixation.

Flexible multi-state switch (FMSS) has flexible power flow adjustment capabilities, which can effectively optimize the power distribution network power flow. In order to reduce the power and voltage fluctuations caused by the distributed generation (DG), connect the DG to the DC side of the FMSS to optimize the input power distribution of the DG. This paper analyzes the topology and mathematical model of the FMSS with joint access to the DG. Considering the feeder load rate and the maximum active power capacity ratio of the feeder, the active power output from the FMSS port connected to each feeder is deduced, and a feeder equalization control strategy for FMSS with joint access to the DG is proposed. A control structure combining a PI controller and a steady-state inverse model was designed for each port of FMSS. The effect of the proposed strategy was verified by building a simulation model of FMSS with joint access to the DG.

We present a double-ballooned catheter that enables both local drug delivery and blood bypassing at the same time. Such catheters are targeted for high-dose local drug treatment of cardiovascular diseases, such as atherosclerosis and restenosis, allowing for extended use without causing downstream ischemia. The device is composed of two flexible balloons that can isolate the lesion under inflation. Local drug delivery can be achieved using the inner catheters while a blood bypassing catheter allows for continuous blood flow. The functionalities of the catheter are validated in both benchtop and live pig experiments.

This paper reports on the first MEMS silicon cutters designed to rapidly section donor pancreatic islets below oxygen diffusion-limited dimensions to improve viability of grafts during the critical period of re-implantation and revascularization by the host. The monolithic silicon chips feature an array of spaced nano-sharp (r < 100 nm) blades that cleanly section islet tissue. This work represents the first time that sectioning of pancreatic islets has been proposed and validated as a means to overcome the well-known problems of hypoxia and core-necrosis that is encountered in current islet transplantation procedures.

We herein present a novel intravascular catheter, with dual-functions of electrical impedance spectroscopy (EIS) and flow fraction reserve (FFR), validated in live pig animal for atherosclerosis/plaques diagnostics. FFR has been the standard tool in determining plaque vulnerability yet could produce false negative results when stenosis is relatively small. Meanwhile, EIS has been demonstrated to specifically distinguish the lipid-rich pool, the signifying feature of rupture-prone plaques. The synergetic performance of these two functionalities can significantly enhance state-of-art diagnostics accuracy for atherosclerosis.

This paper presents a wireless and implantable intraocular pressure (IOP) sensor with parylene-oil-encapsulation packaging using a novel folded PCB architecture accomplishing practical RF coupling for power and data in a rabbit. The sensor is operated with an air gap of 5 mm between the primary coil and the animal, coupling to an on-chip coil at an input power of 32 dBm at 915 MHz, and can also be operated when the eyelid covers the sensor. Additionally, two novel results for parylene-on-oil deposition in general are presented. First, we show that the thickness of the porous layer of parylene-C (PA-C) and parylene-HT (PA-HT) deposited on silicone oils have a logarithmic decrease in porous layer thickness (PLT) versus silicone oil molecular weight (MW) over a range of 2–139 kDa. Second, we directly verify that parylene-oil-encapsulated pressure sensors retain sensitivity despite material buildup for the first time

This paper presents a wireless, implantable continuous intraocular pressure (IOP) monitoring system that features a parylene-on-oil sensor encapsulation method for achieving long-term low-drift in vivo. The system is implanted in the superotemporal quadrant of the eye between the sclera and conjunctiva. It consists of a commercial pressure sensor (STMicroelectronics LPS25H) with digital readout, a 65nm CMOS chip that supports wireless power/data telemetry and the I2C serial communication interface with the pressure sensor. The chip and pressure sensor are assembled on a flexible polyimide PCB, and then the sensor is submerged in biocompatible silicone oil and coated with parylene in situ. The implant uses an on-chip integrated RF coil to receive power from near-field RF coupling at 915 MHz and transmit measurement bits via RF-backscattering to an external reader. A 2 mm × 1.2 mm chip is fabricated in TSMC 65nm CMOS process. The IOP implant achieves a pressure sensitivity of 0.17 mmHg with a total power consumption of 9.7μW. We demonstrate pressure offset drift of less than 0.5 mmHg for more than 4 months over a temperature range of 27–38 °C. The implant successfully tracks induced IOP variations in a porcine eye ex vivo, validating the system functionality and surgical implantation.

A new way to fabricate extremely long and uniform Parylene microcapillaries with a minimum inner diameter of 3 μm and a length exceeding 30 cm is reported here. The method starts with drawing sacrificial poly(ethylene carbonate) (PEC) fibers from its chloroform solution and then forms hollow capillaries by coating the fibers with Parylene and removing the sacrificial PEC at its thermolytic temperature. For the fiber drawing, the relation of fiber diameter to other parameters including drawing speed, fiber aspect ratio, solution viscosity and solvent evaporation rate are studied at 0 and 25 °C. It is found that 0 °C is near the optimal temperature in terms of fiber diameter uniformity. Finally, this work also reports a self-expelling mechanism of the molten PEC at its thermolytic temperature from inside the Parylene-coated PEC fibers, which greatly reduces the sacrificial time to only tens of minutes.

This paper reports on the first phototherapeutic “contact lens” to manage diabetic retinopathy by reducing retinal metabolism via suppression of rod cell dark current. The contact lens is composed of PDMS embedded with a ring of gaseous tritium light sources providing continuous illumination over the lifetime of the lens. Electroretinogram responses from rabbits demonstrate bioactivity of the lens, which is further explored in 1D simulations of retinal oxygenation. Tests in human eyes validate comfort, fit, and the Troxler neural adaptation effect. With oxygen transmissibility, DK/t, of 130 Fatt, the lens meets FDA guidelines for overnight wear and offers advantages of comfort and reliability.

This paper demonstrates a parylene-oil-encapsulated packaging technology that applies to commercial pressure sensors to enable intraocular pressure sensing with minimal drift. Commercial digital-output barometers are chosen to be packaged first with 100,000 cSt silicone oil and then sub-micron thick parylene within the volume of the original housing. It is newly found that parylene type and oil viscosity can decide the sign and magnitude of the intrinsic stress in parylene. Additionally, the effect of deposited thickness and temperature on film stress is studied through induced pressure offset. When properly designed, parylene-oil-encapsulated pressure sensors maintain

This paper reports on the first implantable phototherapy device to treat diabetic retinopathy by modulating rod cell metabolism through reduction of dark current. Utilizing a tritium-based radioluminescent light source capable of emitting around 505nm, the device achieves phototherapeutic activity for up to a 12-year service lifetime and

This paper reports a novel vacuum capillary viscometer featuring small sample volume (1 to 4 μL) and fast turnaround time (less than 30seconds), which allows for the first time, repeatable blood and plasma viscosity measurements from adult zebrafish.

We present a comparative study of the viscoelasticity of parylene C (PPXC) by using Nano-DMA (Dynamical Mechanical Analysis) and Molecular Dynamics (MD) simulations. By applying sinusoidal loading on PPXC films at different temperatures and frequencies, the complex modulus and glass transition temperature (T g ) of the PPXC were obtained. The predicted T g determined from the temperature-dependent density change in the MD model is consistent with the results in our measurements and previous works. Furthermore, with Time-Temperature Superposition Principle (TTSP), we successfully determined the master curve of PPXC, for the first time, which is critical for the parylene reliability study of bio-MEMS devices.

We report for the first time the design, fabrication, and feasibility of a high-density cell culture system capable of a cell substrate density of 40 cm2/cm3, greater than 250× current commercially available systems. This design provides oxygen directly from gas perfusable membranes on which the cells are grown to overcome oxygen delivery limitations in traditional culture systems. With translation in mind, the membranes are composed only of medical grade PDMS and Parylene to mitigate contaminant leaching concerns.

Conventional micro-strip predistortion linearizers work at low band, need isolators to match the input and output and mostly lack of temperature compensation. This paper presents a micro-strip predistortion circuit which can obtain about 5dB and 50° gain and phase expansion at the same bias conditions at 29, 30, 31GHz without isolators at both input and output ports. The diodes in the circuit are parallel with negative temperature coefficient (NTC) thermal resistors.

This paper presents a new MEMS approach of maintaining islet oxygenation for subcutaneous islet transplantation therapy of type 1 diabetes by engineering a MEMS oxygen transport device. A device is designed and fabricated. Bench-top testing and computational modeling of the device have demonstrated that it would provide sufficient oxygen to prevent hypoxia-induced islet death and maintain the functional metabolic activity of glucose-simulated insulin secretion for islets transplanted subcutaneously.

It is of great clinical interest to have easy and reliable diagnostic techniques to localize and identify vulnerable plaques. Here, an in-vivo, catheter-integrated and balloon-mounted Parylene-C micro electrode impedance sensor was developed for intra-vascular interrogation of atherosclerotic vulnerable plaques using Electrical Impedance spectroscopy (EIS). Successful in vivo experiments of the EIS device were demonstrated using high-fat-dieted New Zealand rabbits. The results showed that electrical impedance spectroscopy (EIS) with micro parylene electrodes is promising to distinguish unstable plaques.

This paper reports the first electrolysis-based oxygen generation and transportation device for the treatment of retinal ischemia; containing an isolated biocompatible electrolyte and inductive power transfer for on-demand oxygen. A finite element model of the retina along with oxygen delivery data demonstrates the feasibility of the device. The estimated therapeutic window for the device was found to be 210 minutes for the light adapted retina, and 55 minutes for the dark adapted retina.

This paper reports the feasibility study of a parylene-on-oil encapsulation packaging method of pressure sensors targeted for long-term implantation. Commercial barometric digital-output pressure sensors are enclosed in silicone oil and then encapsulated in situ with parylene-C or -D (PA-C, PA-D). Experimentally, sensors encapsulated with 30,000cSt silicone oil and 24.92μm PA-D show good performance for 6 weeks in 77°C saline with >99% of original sensitivity, corresponding to a predicted lifetime of around 21 months in 37°C saline according to the Arrhenius equation with an activation energy of −0.6eV [1]. This work shows that, with proper designs, such a packaging method can preserve the original pressure sensor sensitivity without offset, validated throughout accelerated lifetime tests. A model to predict sensitivity retention after packaging is also presented.

This paper reports a novel and reliable process to prepare ultra-thin parylene film based on a principle combining both molecular effusion and diffusion. For the first time, a technique for the deposition of parylene film thinner than 20 nm in a highly controllable and repeatable way is developed. Parylene films with various thicknesses could also be prepared in a single deposition run by using this method. This technique holds promising potentials in extensive applications, such as protection/dielectric layer for needle electrodes and flexible electronics, semi-permeable membrane, and other polymer engineering.

Herein, we reported several advanced parylene fabrication techniques for various micro/nano devices by taking advantages of the conformal deposition capability and overcoming related restrictions when depositing in high aspect ratio structures, including deep-trench filling by Parylene C for thermal isolation in silicon microdevices, parylene molding technique for high porosity filter membrane preparation, Parylene C caulked PDMS (pcPDMS) for low permeability microfluidics applications, and ultra-thin parylene deposition for flexible electronics.

Epidural electrostimulation has shown promise for spinal cord injury therapy. However, finding effective stimuli on the multi-electrode stimulating arrays employed requires a laborious manual search of a vast space for each patient. Widespread clinical application of these techniques would be greatly facilitated by an autonomous, algorithmic system which choses stimuli to simultaneously deliver effective therapy and explore this space. We propose a method based on ${\rm GP{\hbox{-}}BUCB}$ , a Gaussian process bandit algorithm. In $n = 4$ spinally transected rats, we implant epidural electrode arrays and examine the algorithm's performance in selecting bipolar stimuli to elicit specified muscle responses. These responses are compared with temporally interleaved intra-animal stimulus selections by a human expert. ${\rm GP{\hbox{-}}BUCB}$ successfully controlled the spinal electrostimulation preparation in 37 testing sessions, selecting 670 stimuli. These sessions included sustained autonomous operations (ten-session duration). Delivered performance with respect to the specified metric was as good as or better than that of the human expert. Despite receiving no information as to anatomically likely locations of effective stimuli, ${\rm GP{\hbox{-}}BUCB}$ also consistently discovered such a pattern. Further, ${\rm GP{\hbox{-}}BUCB}$ was able to extrapolate from previous sessions’ results to make predictions about performance in new testing sessions, while remaining sufficiently flexible to capture temporal variability. These results provide validation for applying automated stimulus selection methods to the problem of spinal cord injury therapy.