PURPOSE:To evaluate the feasibility of surgical implantation of electrical components needed for the operation of biomimetic artificial intraocular lenses (IOLs) for presbyopia correction in phakic non-human primates. This included positioning a ring electrode into the posterior chamber sulcus, securing a circuit board-mounted implant under the superior rectus muscle, and placing a battery pack in the orbit. The full implant allows for recording and transmission of electrical signals within the ciliary muscle during accommodation. METHODS:The implant consists of a microcontroller, a biopotential amplifier, and a Bluetooth transmitter on a flexible printed circuit board (PCB), a battery, and the ring electrode. After mobilization and placement of traction sutures under three muscles, the PCB was positioned under the superior rectus muscle. The ring-shaped electrode was pushed into the anterior chamber via a clear cornea tunnel incision in the upper temporal quadrant. The electrode was carefully advanced under the iris with two forceps to prevent tilting and damaging the anterior capsule until its final position under the iris above the ciliary muscle. RESULTS:During the implantation tests, in two eyes the ring electrode broke during the advancement into the posterior chamber underneath the iris. After optimizing the process, the device was successfully implanted in three eyes of three living phakic primates. An inflammatory response was visible during the postoperative follow-up period, but postmortem histopathological analysis revealed no clinically relevant adverse changes. CONCLUSIONS:The primate model demonstrated the feasibility of the surgical implantation of a circular electrode into the posterior chamber. Regarding future developments of biomimetic accommodative IOLs, a concomitant improvement of surgical techniques and the device is crucial to ensure treatment success.

Ageing results in the progressive loss of near vision, known as presbyopia, which impacts individuals and society. Existing corrective methods offer only partial compensation and do not restore dynamic focusing at varying distances. This work presents a closed-loop correction system for presbyopia, employing biopotential signals from the ciliary muscle and an artificial neural network to predict the eye’s accommodative state in real time. Non-invasive contact lens electrodes collect biopotential data, which are preprocessed and classified using a multi-layer perceptron. The classifier output guides a control system that adjusts an external focus-tunable lens, enabling both accommodation and disaccommodation similar to a young eye. The system demonstrated an accuracy of 0.79, with F1-scores of 0.78 for prediction of accommodation and 0.77 for disaccommodation. Using the system in two presbyopic subjects, near visual acuity improved from 0.28 and 0.38 to 0.04 and −0.03 logMAR, while distance acuity remained stable. Despite challenges such as signal quality and individual variability, the findings demonstrate the feasibility of restoring near-natural accommodation in presbyopia using neuromuscular signals and adaptive lens control. Future research will focus on system validation, expanding the dataset, and pre-clinical testing in implantable devices.

Open-porous structures produced by Additive Manufacturing (AM) offer an excellent basis for patient-specific implants, scaffolds and medical devices. The interface of 3D structures produced by this technology can be improved by the thin-film technology of Atomic Layer Deposition (ALD), a highly modified form of Chemical Vapour Deposition. ALD allows to apply highly conformal coatings on complex geometries and coating of internal surfaces and channels. ALD is a versatile method, as it is compatible with AM. In this work, the conformity of the ALD coating on open-porous structures was investigated. Lattice type cubes of 10x10x10 mm3 outer size and with square channels in all three orthogonal directions with widths of 2’000 μm and 750 μm and two, four or six open sides were produced using masked stereolithography. These additive manufactured open-porous structures were coated with a 75 nm thick titanium oxide (TiO2) layer by ALD. The TiO2 coating thickness was determined on different positions within channels using Scanning Electron Microscopy (SEM). The measurements revealed excellent coating conformity over the internal surfaces (82.1 ± 2.6 nm and 87.9 ± 3.8 nm in 2’000 μm and 750 μm channels, respectively) with a Uniformity Index of up to 7.8%: The results highlight the potential of combining 3D printing and ALD to overcome existing technical limitations and enhance the functionality, biocompatibility, and durability of advanced materials for medical applications.

Crack based strain sensors (CBSS) are a promising technological platform outperforming traditional strain sensors. The electromechanical characteristics are highly dependent on the loading scenario and change significantly between initial priming and subsequent cycling. In the present work, we present in-situ morphology data of the metal film crack evolution during such priming sequences and provide new insights to the evolution of network cracks. Comparing uniaxial and biaxial loading with subsequent cycles underlines the importance of the initial crack formation for later sensing capabilities and further explains the different electromechanical characteristics during priming.

To see near objects clearly, the ciliary muscle shapes the human eye's crystalline lens to adjust its refractive power, a process known as accommodation. This contraction of the ciliary muscle also results in an electrical potential change. Previous work from the 1950s and 1960s reported electrical voltages in the microvolt range that were attributed to the accommodating ciliary muscle, however without clarifying the interaction between lens and muscle. Here, we present data of 12 emmetropic participants using a custom-developed scleral contact lens electrode which enables to record accommodation-dependent biopotentials of the ciliary muscle with an accuracy up to the millivolt range. Therefore, participants alternately shifted their focus from far to various near targets while the biopotentials of the ciliary muscle and the actual refractive change of the crystalline lens were recorded by a contact lens electrode and an eccentric infrared Photorefractor. In addition, the impact of confounding biopotentials such as squinting and eye movements was investigated. Our research points to a potentially new objective method of measuring accommodative change. Understanding these biopotentials could lead to the development of self-focusing visual aids as an alternative way of vision correction in presbyopes.

We conducted a proof-of-concept study for an additively manufactured complex 3D electrode structure for anal neuromonitoring using silver resin. Recent developments in additive manufacturing promise significant advantages for prototyping medical sensors. These prototypes are scalable and customisable, with a variety of biocompatible 3D-printable materials available at reasonable manufacturing costs and an increasing range of printable conductive materials. However, difficulties arise in reaching stable conductivity in complex electrode configurations. Since reliable conductive properties are key characteristics of biomedical sensors, we aimed to find an experimental setup that mimics the signal propagation of connective tissue and allows for spatial resolution of signals for rapid self-testing of multi-electrode sensors.

The measurement of electrical potentials in the human body is becoming increasingly important in healthcare as a valuable diagnostic parameter. In ophthalmology, while these signals are primarily used to assess retinal function, other applications, such as recording accommodation-related biopotentials from the ciliary muscle, remain poorly understood. Here, we present the development and evaluation of a novel implantable ring electrode for recording biopotentials from the ciliary muscle. Inspired by capsular tension rings, the electrode was fabricated using laser cutting, wiring, and physical vapor deposition coating. The constant impedance and weight over a simulated aging period of 391 days, demonstrated the electrode’s stability. In vivo testing in non-human primates further validated the electrode’s surgical handling and long-term stability, with no delamination or tissue ingrowth after 100 days of implantation. Recorded biopotentials from the ciliary muscle (up to 700 µV) exceeded amplitudes reported in the literature. While the results are promising, further research is needed to investigate the signal quality and origin as well as the correlation between these signals and ciliary muscle activity. Ultimately, this electrode will be used in an implanted device to record ciliary muscle biopotentials to control an artificial lens designed to restore accommodation in individuals with presbyopia.

Area-selective atomic layer deposition (ASD) is a bottom-up process that is of particular importance in the semiconductor industry, as it prevents edge defects and avoids cost-intensive lithography steps. This approach not only offers immense potential for the manufacture of active implants but can also be used to improve them. This review paper presents various processes that can be used for this purpose. It also identifies aspects that shall be considered when implementing such a process for medical applications. For example, the inherent selectivity can be used to produce new biosensors, the passivated ASD can be used to encapsulate polymer-based implants, and the activated ASD can be used to improve electrode performance. Finally, the aspects that shall be considered in a coating for active implants are highlighted. ASD therefore offers great potential for use on active implants.

This article provides a detailed morphological and spectroscopic investigation of a porous silicon-based technique for fabricating ultra-broadband infrared (IR) optical filter elements that integrate surface and subsurface structures, and which are suitable for applications in thermal imaging, sensing and infrared spectroscopy. The porous silicon (PSi)-based absorber consists of a light trapping (islet-like) surface and a multilayer structure forming quarter-wave thick layers as anti-reflective structure underneath. These integrated structures can be created and combined by two electrochemical etching processes with different etchant concentrations, current densities, and etch times to provide both, fully light absorbing, and anti-reflective coatings (ARC). The integrated porous silicon-based anti-reflective and light trapping structure has an extremely low specular reflectance of less than 0.03% and an extremely low transmission of less than 0.1% in a wide wavenumber range of 4000 - 600 cm(-1). The hemispherical reflectance (HR) shows a decreasing trend down to 5% at 1500 cm(-1). The absorbance of the investigated absorber is calculated using the Kirchoff's law of the radiation.

Parylene C is well-known as an encapsulation material for medical implants. Within the approach of miniaturization and automatization of a bone distractor, piezoelectric actuators were encapsulated with Parylene C. The stretchability of the polymer was investigated with respect to the encapsulation functionality of piezoelectric chips. We determined a linear yield strain of 1% of approximately 12-µm-thick Parylene C foil. Parylene C encapsulation withstands the mechanical stress of a minimum of 5×105 duty cycles by continuous actuation. The experiments demonstrate that elongation of the encapsulation on piezoelectric actuators and thus the elongation of Parylene C up to 0.8 mm are feasible.

Low-frequency noise is investigated of CMOS devices equipped with a dielectric sensor interface to an electrolyte. A related test methodology is suggested to characterize the sensor dielectric’s noise, and a model is derived to describe the dielectric’s contribution to the total noise.

Plasma-enhanced atomic layer deposition (PEALD) is utilized to improve the barrier properties of an organic chip-film patch (CFP) when it is used as an implant to prevent moisture and ions from migrating into the embedded electronic circuits. For this purpose, surface condition and material properties of eight modifications of Al2O3–TiO2 nanolaminates sequentially deposited on polyimide PI-2611 films are evaluated in detail. The effect of stress-induced warpage of the deposited Al2O3–TiO2 on the wafer level is calculated with the Stoney equation and reveals higher tensile stress values while increasing the thickness of Al2O3–TiO2 nanolaminates from 20 up to 80 nm. Contact angle measurement and atomic force microscopy are used to investigate the surface energy and wettability, as well as the surface morphology of polyimide–Al2O3–TiO2 interfaces. We show that plasma treatment of pristine polyimide leads to an enhanced adhesion force of the PEAL-deposited layer by a factor of 1.3. The water vapor transmission rate (WVTR) is determined by exposing the coated polyimide films to 85% humidity and 23 °C and yields down to 1.58 × 10–3 g(H2O)/(m2 d). The data obtained are compared with alternative coating processes using the polymers parylene-C and benzocyclobutene (BCB). The latter shows higher WVTR values of 1.2 × 10–1 and 1.7 × 10–1 g(H2O)/(m2 d) compared to the PEALD–PI-2611 systems, indicating lower barrier properties. Two Al2O3–TiO2 modifications with low WVTR values have been chosen for encapsulating the CFP substrates and exposing them in a long-time experiment to chemical and mechanical loads in a chamber filled with phosphate-buffered saline at 37 °C, pH 7.3, and a cyclically applied pressure of 160 mbar (∼120 mm Hg). The electrical leakage behavior of the CFP systems is measured and reveals reliable electrical long-term stability far beyond 11 months, highlighting the great potential of PEALD-encapsulated CFPs.

Chitosan derivatives substituted with benzophenone groups that can be cross-linked by ultraviolet light were synthesized as coatings for PEEK substrates used in the construction of lumbar cages. The IC90 values of the benzophenone-modified chitosan polymers in solution before crosslinking were in the same range as those reported for native chitosan. The resulting hydrogel surface after crosslinking exhibited excellent antimicrobial properties and was highly effective (up to 5 log-fold) against clinically relevant strains of methicillin-resistant S. aureus and E. coli. As a result, the coated surface also signifi-cantly reduced biofilm formation. The coatings show good biocompatibility with numerous cell lines as well as low levels of cytotoxicity (ISO 10993-5) and pyrogenicity (ISO 10993-11). The coatings also exhibited strong antioxidant properties toward formed hydroxyl radicals in an in-vitro Fenton reaction. Overall, substitution of chitosan with benzophenone residues is an interesting and important approach to the functionalization of materials used for medical implants that are prone to microbial contamination and mechanical failure. Biocompatible antimicrobial coatings might also be employed in photopatterning methods used in the design of medical devices.(c) 2022 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Presbyopia describes the eye's physiological loss of the ability to see close objects clearly. The adaptation to different viewing distances, termed accommodation, is achieved by a change in the curvature of the eye lens induced by the ciliary muscle. A possible approach to correct presbyopia could be to detect the ciliary muscle's neuromuscular signals during accommodation and transfer these signals electronically to a biomimetic, micro-optical system to provide the necessary refractive power. As a preliminary step toward such a described system, a novel three-dimensional and biocompatible lift-off method was developed. In addition, the influence of the distance between the electrically conducting surfaces of the lens on the accommodated signal amplitudes was investigated. Compared to the conventional masking methods, this process has the advantage that three-dimensional surfaces can be masked with biocompatible gelling sugar by utilizing a direct writing process with a dispensing robot. Since gelling sugar can be used at room temperature and is water-soluble, the process presented is suitable for materials that should not be exposed to organic solvents or excessively high temperatures. Apart from investigating the shrinkage behavior of the gelling sugar during the physical vapor deposition (PVD) coating process, this paper also describes the approaches used to partially coat a commercial scleral contact lens with an electrically conductive material. It was shown that gelling sugar withstands the conditions during the PVD processes and a successful lift-off was performed. To investigate the influence of the spacing between the electrically conductive regions of the contact lens on the measured signals, three simplified electrode configurations with different distances were fabricated using a 3D printer. By testing these in an experimental setup, it could be demonstrated that the distance between the conductive surfaces has a significant influence on the amplitude. Regarding the described lift-off process using gelling sugar, it was found that the dispensing flow rate has a direct influence on the line uniformity. Future work should address the influence of the viscosity of the gelling sugar as well as the diameter of the cannula. It is assumed that they are the prevailing limitations for the lateral resolution.

Encapsulation is essential for mechanically flexible and electrically active implants as it protects them from the harsh environment inside the body. Since the performance and longevity of implants depends on the quality of encapsulation, research continues into new and better encapsulation strategies. Chemical vapour deposition can be used to deposit Parylene-C, a biocompatible polymer, at room temperature. Plasma enhanced atomic layer deposition can be used to deposit ultra-thin, conformal, and hermetic metal oxide layers. These strategies are both used for the encapsulation of implants. In this work, these two methods are combined to create a polymer/metal oxide hybrid system in which a layer system of metal oxides is sandwiched between two Parylene- C layers. DC leakage-current measurement and elevated temperature are used to qualify the barrier property of the layer-system. After more than one year, the barrier properties still show no significant decrease.

Abstract High quality recording of neuronal activities and electrical stimulation require neurotechnical implants with appropriate electrode material. Iridium oxide (IrOx) is an excellent choice of material due to its biocompatibility, low electrochemical impedance, superior charge injection capacity, corrosion resistance, longevity, and electrochemical stability. Plasma enhanced atomic layer deposition (PE-ALD) and a suitable precursor, like (Methylcyclopentadienyl) (1,5- cyclooctadiene) iridium, could be a promising technique to produce highly conformal and performant IrOx-films at low temperatures and low costs. Various studies have reported the deposition of iridium oxide, but usually at very high temperatures. These processes are not suitable for polymer substrates and limit the use of such post-processing together with active implants. In this work the (Methylcyclopentadienyl) (1,5-cyclooctadiene) iridium(I) ((MeCp)Ir(COD)) precursor was used as a promising approach for depositing IrOx-films using low temperature PE-ALD. This precursor is normally used for chemical vapour deposition processes. First experiments were carried out on silicon substrates at deposition temperatures of 110 C°. The precursor was heated up to 75 °C and oxygen plasma was used as coreactant. The deposited films were analysed with EDX and AFM, showing a smooth surface and a promising ratio between the elements iridium and oxygen.

For the encapsulation of microelectronics or active implants, hermetically sealed, thin, and flexible materials are desirable. Research is focused on the deposition of ultra-thin metal oxide layers, which are deposited onto the substrates using the atomic layer deposition (ALD) process. The evaluation of such layers can be performed by the so-called water vapor transmission rate (WVTR). We present an inexpensive method for the determination of the effective WVTR by humidity sensors and a suitable experimental setup, in which we have measured three different layer systems with four different total thicknesses, which were applied on polymer films, for validation.