Development of a fabrication process for production of diffractive optics.

In this study, a novel fabrication process, to the best of our knowledge, was developed to fabricate a glass harmonic diffractive lens. In this process, a polymethylmethacrylate master of the diffractive lens was machined using single-point diamond turning. Then an electrolytic plating process was conducted to grow a reverse nickel (Ni) mold. Precision compression molding was performed using the Ni mold to replicate the diffractive lens structures onto a glass surface. Surface measurements and optical testing show that the replicated diffractive lenses by the proposed method have high tolerances and require optical performance, demonstrating a high-volume, high-precision, and cost-effective process. The proposed method will be critical for consumer products where glass optics are increasingly used in lens assemblies.

Spirituality and Wellness in Plastic Surgery: A Survey of ASPS Members.

Spirituality is an important, yet often overlooked, component of personal well-being. The purpose of this study was to assess whether spirituality plays an important role in the well-being of US plastic surgeons and residents, and whether spirituality is viewed as an important component of patient care. METHODS: An anonymous and voluntary email survey was distributed to 3375 members of ASPS during the months of April through June of 2020. The survey distribution included 2230 active members of ASPS and 1149 resident members, all who practice or train within the United States. The survey consisted of 18 multiple-choice questions with answer choices based on a descriptive five-point Likert scale and ranking by priority. Statistical analysis of the results was performed using StataCorp 2019 software. RESULTS: A total of 431 completed surveys were received for a response rate of 12.7%. The majority of participants (70%) reported that personal spiritual beliefs and faith contribute positively to emotional well-being. In total, 65% agreed or strongly agreed that their spiritual beliefs provide a healthy framework for handling conflict, suffering, and loss. More than half (51%) reported that as a result of the COVID-19 global pandemic, their spiritual beliefs and practices have provided increased support and guidance. CONCLUSIONS: Spirituality is an important component of maintaining wellness for plastic surgeons, and spirituality is recognized by plastic surgeons as an important aspect of the healing process for patients. Efforts should be made to promote spiritual health among the surgical community both during training and in practice.

Investigation of mid-infrared rapid heating of a carbide-bonded graphene coating and its applications in precision optical molding.

Graphene interacts with electromagnetic waves strongly in a wide range from ultra-violet to far-infrared, making the graphene coating suitable for a variety of applications. In this study, a novel localized rapid heating technique utilizing micro-patterned silicon stampers with carbide-bonded graphene coating, which directly heats up by absorbing mid-infrared light radiation, is implemented in rapid precision optical molding. The graphene network, as a functional coating to obtain thermal energy and improve the anti-adhesion of the mold surface, can heat up the mold surface rapidly (up to 18.16 K/s) and evenly above glass transition temperature over a large area within several seconds. Since the graphene coating was around tens of nanometers (∼45 nm) thick, the rapid precision surface molding process can be shortened into tens of seconds. Furthermore, the thermal response and repeatability of the graphene coated silicon wafer is investigated by repeated thermal cycling. This novel rapid precision surface molding technique is successfully tested to replicate grating structures and periodic patterns from silicon molds to thermoplastic substrates with high accuracy. Compared with conventional methods, this new approach can achieve much higher replication fidelity with a shorter cycle time and lower energy consumption.

Incidence of Venous Thromboembolism after Sternal Reconstruction: A Single-center Retrospective Review.

BACKGROUND: Deep sternal wound infection and mediastinitis following sternotomy are associated with significant morbidity and mortality, and often require sternal reconstruction by plastic surgeons. Despite this patient population having a substantial risk of venous thromboembolism, there are no reports of the incidence of venous thromboembolism in patients undergoing sternal reconstruction. The authors sought to evaluate the incidence of venous thromboembolism in sternal reconstruction patients and to identify common risk factors for venous thromboembolism in this patient population. METHODS: A single-center retrospective review was completed of all patients who underwent sternal reconstruction by plastic surgeons between January 2012 and July 2020. Demographic data, antiplatelet and anticoagulant use, 2005 Caprini score, operative time, bleeding events, and postoperative venous thromboembolism events were recorded. RESULTS: A total of 44 patients were identified for analysis. The average 2005 Caprini score for the cohort was 10.9. In total, 93.2% of patients received perioperative antiplatelet and anticoagulant therapy (either chemoprophylaxis or systemic). Two patients developed postoperative venous thromboembolism events, for a total venous thromboembolism rate of 4.6%. Four patients had bleeding events requiring reoperation. No deaths were reported from either of these complications. CONCLUSIONS: Patients undergoing sternal reconstruction are at a high risk for venous thromboembolism and postoperative bleeding events. Despite the growing body of literature on venous thromboembolism in various surgical populations, the optimal management of thromboembolic risk in patients with high Caprini scores undergoing sternal reconstruction requires additional investigation.

Follistatin-induced muscle hypertrophy in aged mice improves neuromuscular junction innervation and function.

Sarcopenia, or age-related loss of muscle mass and strength, is an important contributor to loss of physical function in older adults. The pathogenesis of sarcopenia is likely multifactorial, but recently the role of neurological degeneration, such as motor unit loss, has received increased attention. Here, we investigated the longitudinal effects of muscle hypertrophy (via overexpression of human follistatin, a myostatin antagonist) on neuromuscular integrity in C57BL/6J mice between the ages of 24 and 27 months. Following follistatin overexpression (delivered via self-complementary adeno-associated virus subtype 9 injection), muscle weight and torque production were significantly improved. Follistatin treatment resulted in improvements of neuromuscular junction innervation and transmission but had no impact on age-related losses of motor units. These studies demonstrate that follistatin overexpression-induced muscle hypertrophy not only increased muscle weight and torque production but also countered age-related degeneration at the neuromuscular junction in mice.

Fabrication of Fresnel lens arrays by a rapid non-isothermal imprinting process.

Fresnel lens arrays are widely employed in concentrator photovoltaics, photonic devices, and integral imaging systems. In this study, a rapid non-isothermal imprinting process for Fresnel lens arrays was proposed. In this process, a heated mold with microstructures was momentarily pressed onto a thermoplastic polymer surface that was initially kept at room temperature. The microstructures of the mold can be copied completely to the polymer substrate by imprinting consecutively until a continuous surface Fresnel lens array is obtained. Different from more traditional molding processes, the substrate does not need to be heated and cooled repeatedly in the replicating process. In addition, the imprinting process is carried out at room temperature, which can greatly reduce the thermal cycle time and energy consumption. Generally speaking, the material flow and stress distribution of the substrate need to be monitored so that the microlenses with a high precision surface finish can be produced in the non-isothermal imprinting process. To verify this, the finite element method (FEM) model for the non-isothermal process was established, and the feasibility of this process was analyzed. A hexagonal continuous surface Fresnel lens array was then fabricated, and its geometrical contour and imaging performance were tested. The experimental results showed this new process could be an effective and low-cost optical fabrication technology for high-quality production of Fresnel lens arrays.

Precision glass molding of diffractive optical elements with high surface quality.

Diffractive optical surfaces have attractive properties for use in optical systems, like reducing weight and correcting for chromatic aberrations, but fabrication of high-quality glass diffractive optics is challenging, preventing it from being widely adopted in commercial applications. In this Letter, we report on a fabrication method to address molding challenges for high-surface-quality diffractive glass optics at molding temperatures up to 550°C, including selection of mold material, mold fabrication, precision glass molding, durability, and stability of the mold. To enable optimal mold machining and easy mold release, nickel phosphorous (NiP) is chosen as the plating material for its cutting performance and anti-adhesion properties, and copper-nickel C71500 (CuNi) is selected as the mold substrate because its coefficient of thermal expansion (CTE) is close to NiP. By the proposed method, diffractive glass optics with 2 nm Sa surface roughness is demonstrated.

Manufacturing of a microlens array mold by a two-step method combining microindentation and precision polishing.

A novel two-step method for manufacturing microlens array molds by combining microindentation and precision polishing is proposed. Compared with conventional manufacturing methods, such as single-point diamond turning, this two-step method, as an alternative method, presents great advantages on cost and flexibility on spherical microlens array mold fabrication. Various curvatures of radii and arrangements for microlens array molds can be fabricated in the same way. In this paper, a hexagonal microlens array with 1.58 mm curvature radius was demonstrated to prove the feasibility of the proposed method. First, a large number of precise steel balls were organized in hexagonal arrangement and pressed into the mold's surface to generate multiple microdimples. Second, the pileups around the microdimples were removed from the mold surface by precision polishing. The geometrical accuracy and surface quality were investigated by an optical surface profiler. The measurement indicated that, compared with the initial surface, the surface inside the dimple had significantly higher hardness and better surface quality than that of the steel balls. Then the microlens array on the mold was further replicated to poly(methyl methacrylate) substrates by a precision compression molding process. The experimental results showed that the fabricated mold and the polymer replicas have high fidelity, great uniformity, and good surface roughness. The proposed two-step, low-cost mold fabrication method can produce highly uniform microlens arrays and is therefore suitable for high-volume fabrication of precise optical elements such as integrated light-emitting diodes and other similar micro-optics.

Fabrication of aspherical polymeric lenses using tunable ferrogel molds.

The majority of optical lenses have spherical surface profiles because they are convenient to fabricate. Replacing spherical optics with aspheric optics leads to smaller size, lighter weight, and less complicated optical systems with a superior imaging quality. However, fabrication of aspheric lenses is expensive and time-consuming. Here, we introduce a straightforward and low-cost casting method to fabricate polymeric aspheric lenses. An elastomeric ferrogel was formed into an aspherical profile by using a designed magnetic field and then was used as a mold. Different types of aspherical profiles from parabola to hyperbola can be formed with this method by tuning the magnetic field. A home-built Shack-Hartmann sensor was employed to characterize the cast polymeric lenses. The effects of magnetic field intensity, gradient of the magnetic field, and magnetic susceptibility of the ferrogel on the lens profiles were investigated. This technique can be used for rapid-forming polymeric aspherical lenses with different sizes and shapes.

Effects of Machining Errors on Optical Performance of Optical Aspheric Components in Ultra-Precision Diamond Turning.

Optical aspheric components are inevitably affected by various disturbances during their precision machining, which reduces the actual machining accuracy and affects the optical performance of components. In this paper, based on the theory of multi-body system, we established a machining error model for optical aspheric surface machined by fast tool servo turning and analyzed the effect of the geometric errors on the machining accuracy of optical aspheric surface. We used the method of ray tracing to analyze the effect of the surface form distortion caused by the machining error on the optical performance, and identified the main machining errors according to the optical performance. Finally, the aspheric surface was successfully applied to the design of optical lens components for an aerial camera. Our research has a certain guiding significance for the identification and compensation of machining errors of optical components.

Development of a Novel Three Degrees-of-Freedom Rotary Vibration-Assisted Micropolishing System Based on Piezoelectric Actuation.

The limited degrees of freedom (DOF) and movement form of the compliant vibration-assisted processing device are inherent constraints of the polishing technique. In this paper, a concept of a 3-DOF rotary vibration-assisted micropolishing system (3D RVMS) is proposed and demonstrated. The 3-DOF means the proposed vibration-assisted polishing device (VPD) is driven by three piezo-electric (PZT) actuators. Compared with the current vibration-assisted polishing technology which generates a trajectory with orthogonal actuators or parallel actuators, a novel 3-DOF piezoelectrically actuated VPD was designed to enable the workpiece to move along the rotational direction. Meanwhile, the proposed VPD can deliver large processing stoke in mrad scale and can be operated at a flexible non-resonant mode. A matrix-based compliance modeling method was adopted for calculating the compliance and amplification ratio of the VPD. Additionally, the dynamic and static properties of the developed VPD were verified using finite element analysis. Then, the VPD was manufactured and experimentally tested to investigate its practical performance. Finally, various polished surfaces which used silicon carbide (SiC) ceramic as workpiece material were uniformly generated by the high-performance 3D RVMS. Compared with a nonvibration polishing system, surface roughness was clearly improved by introducing rotary vibration-assisted processing. Both the analysis and experiments verified the effectiveness of the present 3D RVMS for micro-machining surfaces.

Analytical Prediction of Subsurface Damages and Surface Quality in Vibration-Assisted Polishing Process of Silicon Carbide Ceramics.

Subsurface damages and surface roughness are two significant parameters which determine the performance of silicon carbide (SiC) ceramics. Subsurface damages (SSD) induced by conventional polishing could seriously affect the service life of the workpiece. To address this problem, vibration-assisted polishing (VAP) was developed to machine hard and brittle materials, because the vibration-assisted machine (VAM) can increase the critical cutting depth to improve the surface integrity of materials. In this paper, a two-dimensional (2D) VAM system is used to polish SiC ceramics. Moreover, a theoretical SSD model is constructed to predict the SSD. Furthermore, finite element simulation (FEM) is adopted to analyze the effects of different VAP parameters on SSD. Finally, a series of scratches and VAP experiments are conducted on the independent precision polishing machine to investigate the effects of polishing parameters on brittle-ductile transition and SSD.

Fabrication of Plano-Concave Plastic Lens by Novel Injection Molding Using Carbide-Bonded Graphene-Coated Silica Molds.

Injection molding of plastic optical lenses prevails over many other techniques in both efficiency and cost, however polymer shrinkage during cooling, high level of uneven residual stresses and refractive index variations have limited its potential use for high precision lenses fabrication. In this research, we adopted a newly-developed strong graphene network to both plain and convex fused silica mold surfaces and proposed a novel injection molding of plano-concave lenses with graphene coated fused silica molds. The unique combination of the graphene coating and fused silica substrate maximize the mechanical properties of the mold and coating materials, namely high hardness, low surface friction, and high heat preservation effect during cooling since fused silica has low thermal conductivity. This advanced injection molding process was implemented in molding of plano-concave lenses resulting in reduced polymer shrinkage. In addition, internal residual stresses, and refractive index variations were also analyzed and discussed in detail. Meanwhile, as a comparison of conventional injection mold material, aluminum mold inserts with the same shape and size were also diamond machined and then employed to mold the same plano-concave lenses. Finally, a simulation model using Moldex3D was utilized to interpret stress distributions of both graphene and aluminum molds and then validated by experiments. The comparison between graphene and aluminum molds reveals that the novel injection molding with carbide-bonded graphene coated fused silica mold inserts is capable of molding high quality optical lenses with much less shrinkage and residual stresses, but more uniform refractive index distribution.

Investigation of thermoforming mechanism and optical properties' change of chalcogenide glass in precision glass molding.

Chalcogenide glasses are emerging as enabling materials for low-cost infrared optics due to their transparency in shortwave-to-longwave infrared bands and the possibility to be mass produced by precision glass molding (PGM), a near net-shape process. This paper aims to evaluate the thermoforming mechanism of As40S60 glass around its glass transition temperature (Tg) and investigate its refractive index change and residual stresses in a molded lens during and after PGM. First, a constitutive model was introduced to precisely predict the material behavior in PGM by integrating subroutines into a commercial finite element analysis (FEA) software. This modeling approach utilizes the Williams-Landel-Ferry equation and Tool-Narayanaswamy-Moynihan model to describe stress relaxation and structural relaxation behaviors, respectively. The numerical simulation revealed that the cooling rate above glass transition temperature (Tg) can introduce large geometry deviations to the molded optical lens. The residual stresses in a molded lens are generated mainly at the temperature around Tg due to the heterogeneity of thermal expansion from viscoelastic to solid state, while structural relaxation occurs during the entire cooling process. The refractive index variations inside molded lenses were predicted by performing finite element method simulation and further evaluated by measuring wavefront changes using an infrared Shack-Hartmann wavefront sensor, while the residual stresses trapped inside the molded lenses were obtained by using a birefringence method. A combination of measurements of the molded infrared lenses and numerical simulation results provided an opportunity for optical manufacturers to better understand the mechanism and optical performance of chalcogenide glasses during and after PGM.

Investigation of index change in compression molding of As40Se50S10 chalcogenide glass.

Chalcogenide glasses are emerging as alternative materials for low-cost and high-volume glass molding processes for infrared optics. In precision glass molding, it is well documented that the refractive index variation in the molded elements can lead to substantial amounts of aberrations. The variation has such a significant effect that the optical designs with molded lenses need to be carefully considered and compensated for index variation to achieve targeted optical performance. This research is aimed to evaluate the refractive index change of a chalcogenide glass during the molding process by both finite element method-based simulation and optical experiment. First, a set of mold inserts was designed and machined by high-speed single-point diamond milling. The structure of the lower mold insert was semiclosed and detachable, which facilitated the molded infrared prisms' release from the mold. Second, finite element method simulation was implemented to predict the refractive index change during the cooling phase by using the Tool-Narayanaswamy-Moynihan model for structural relaxation behavior. It was confirmed that refractive index variation occurred inside the molded wedge due to rapid thermal cycling. However, the amount of variation in the molded element indicates that the refractive index change during the molding process was not uniform. Finally, the refractive index of the molded wedge was measured by an optical setup. The results showed that the index shift is approximately -0.0226 for As40Se50S10, which matched the numerical result by simulation. Compared with oxide glass materials, the index drop of As40Se50S10 has a significant effect on optical performance of molded optics, and the postmolding refractive index should be taken into account in the optical design. In summary, the results presented in this article provided reliable references for refractive index change of As40Se50S10 glass, crucial for precision glass molding or similar applications.

Fabrication of an infrared Shack-Hartmann sensor by combining high-speed single-point diamond milling and precision compression molding processes.

A novel fabrication method by combining high-speed single-point diamond milling and precision compression molding processes for fabrication of discontinuous freeform microlens arrays was proposed. Compared with slow tool servo diamond broaching, high-speed single-point diamond milling was selected for its flexibility in the fabrication of true 3D optical surfaces with discontinuous features. The advantage of single-point diamond milling is that the surface features can be constructed sequentially by spacing the axes of a virtual spindle at arbitrary positions based on the combination of rotational and translational motions of both the high-speed spindle and linear slides. By employing this method, each micro-lenslet was regarded as a microstructure cell by passing the axis of the virtual spindle through the vertex of each cell. An optimization arithmetic based on minimum-area fabrication was introduced to the machining process to further increase the machining efficiency. After the mold insert was machined, it was employed to replicate the microlens array onto chalcogenide glass. In the ensuing optical measurement, the self-built Shack-Hartmann wavefront sensor was proven to be accurate in detecting an infrared wavefront by both experiments and numerical simulation. The combined results showed that precision compression molding of chalcogenide glasses could be an economic and precision optical fabrication technology for high-volume production of infrared optics.

Tonic B-cell receptor signaling in diffuse large B-cell lymphoma.

We used clustered regularly interspaced short palindromic repeats/Cas9-mediated genomic modification to investigate B-cell receptor (BCR) signaling in cell lines of diffuse large B-cell lymphoma (DLBCL). Three manipulations that altered BCR genes without affecting surface BCR levels showed that BCR signaling differs between the germinal center B-cell (GCB) subtype, which is insensitive to Bruton tyrosine kinase inhibition by ibrutinib, and the activated B-cell (ABC) subtype. Replacing antigen-binding BCR regions had no effect on BCR signaling in GCB-DLBCL lines, reflecting this subtype's exclusive use of tonic BCR signaling. Conversely, Y188F mutation in the immunoreceptor tyrosine-based activation motif of CD79A inhibited tonic BCR signaling in GCB-DLBCL lines but did not affect their calcium flux after BCR cross-linking or the proliferation of otherwise-unmodified ABC-DLBCL lines. CD79A-GFP fusion showed BCR clustering or diffuse distribution, respectively, in lines of ABC and GCB subtypes. Tonic BCR signaling acts principally to activate AKT, and forced activation of AKT rescued GCB-DLBCL lines from knockout (KO) of the BCR or 2 mediators of tonic BCR signaling, SYK and CD19. The magnitude and importance of tonic BCR signaling to proliferation and size of GCB-DLBCL lines, shown by the effect of BCR KO, was highly variable; in contrast, pan-AKT KO was uniformly toxic. This discrepancy was explained by finding that BCR KO-induced changes in AKT activity (measured by gene expression, CXCR4 level, and a fluorescent reporter) correlated with changes in proliferation and with baseline BCR surface density. PTEN protein expression and BCR surface density may influence clinical response to therapeutic inhibition of tonic BCR signaling in DLBCL.

Rapid localized heating of graphene coating on a silicon mold by induction for precision molding of polymer optics.

In compression molding of polymer optical components with micro/nanoscale surface features, rapid heating of the mold surface is critical for the implementation of this technology for large-scale applications. In this Letter, a novel method of a localized rapid heating process is reported. This process is based on induction heating of a thin conductive coating deposited on a silicon mold. Since the graphene coating is very thin (∼45 nm), a high heating rate of 10∼20°C/s can be achieved by employing a 1200 W 30 kHz electrical power unit. Under this condition, the graphene-coated surface and the polymer substrate can be heated above the polymer's glass transition temperature within 30 s and subsequently cooled down to room temperature within several tens of seconds after molding, resulting in an overall thermal cycle of about 3 min or shorter. The feasibility of this process was validated by fabrication of optical gratings, micropillar matrices, and microlens arrays on polymethylmethacrylate (PMMA) substrates with very high precision. The uniformity and surface geometries of the replicated optical elements are evaluated using an optical profilometer, a diffraction test setup, and a Shack-Hartmann wavefront sensor built with a molded PMMA microlens array. Compared with the conventional bulk heating molding process, this novel rapid localized induction heating process could improve replication efficiency with better geometrical fidelity.

Design, fabrication, and testing of a Shack-Hartmann sensor with an automatic registration feature.

In this research, design, construction, and testing of an innovative Shack-Hartmann sensor are described. As the most critical component, a polymer microlens array is injection molded and mounted on a board-level CMOS camera such that the focal plane of the microlens array is on the camera's image plane. To allow for automatic registration of the spots of the measured area, a diffusing surface was created at the center of the lens array in the same diamond machining process in an uninterrupted operation. This unique diffusing surface does not generate an image spot. The no-spot feature functions as the reference in the measurement on the camera's image plane. Using this unique feature, large global tip-tilt error can be detected and eliminated. In this research, both experiments and simulation have shown that the Shack-Hartmann sensor built using low cost components is capable of precision wavefront detection. This research also demonstrated that automatic registration based on the diffusing surface is simple and reliable.

Optical performance simulation of free-form optics for an eye implant based on a measurement data enhanced model.

This paper describes the application of a modeling approach for precise optical performance prediction of free-form optics-based subsystems on a demonstration model of an eye implant. The simulation model is enhanced by surface data measured on the free-form lens parts. The manufacturing of the free-form lens parts is realized by two different manufacturing processes: ultraprecision diamond machining and microinjection molding. Evaluation of both processes is conducted by a simulation of the optical performance on the basis of their surface measurement comparisons with the nominal geometry. The simulation results indicate that improvements from the process optimization of microinjection molding were obtained for the best manufacturing accuracy.