Search Results (73)

Glass-based microfluidic devices are essential for applications such as diagnostics and drug discovery, which utilize their optical clarity and chemical stability. This review systematically analyzes pulsed laser micromachining as a transformative technique for fabricating glass-based microfluidic devices, addressing the limitations of conventional methods. By examining three pulse regimes—long (≥nanosecond), short (picosecond), and ultrashort (femtosecond)—this study evaluates how laser parameters (fluence, scanning speed, pulse duration, repetition rate, wavelength) and glass properties influence ablation efficiency and quality. A higher fluence improves the material ablation efficiency across all the regimes but poses risks of thermal damage or plasma shielding in ultrashort pulses. Optimizing the scanning speed balances the depth and the surface quality, with slower speeds enhancing the channel depth but requiring heat accumulation mitigation. Shorter pulses (femtosecond regime) achieve greater precision (feature resolution) and minimal heat-affected zones through nonlinear absorption, while long pulses enable rapid deep-channel fabrication but with increased thermal stress. Elevating the repetition rate improves the material ablation rates but reduces the surface quality. The influence of wavelength on efficiency and quality varies across the three pulse regimes. Material selection is critical to outcomes and potential applications: fused silica demonstrates a superior surface quality due to low thermal expansion, while soda–lime glass provides cost-effective prototyping. The review emphasizes the advantages of laser micromachining and the benefits of a wide range of applications. Future directions should focus on optimizing the process parameters to improve the efficiency and quality of the produced devices at a lower cost to expand their uses in biomedical, environmental, and quantum applications. Full article

The rapid development of microfluidics has driven innovations in material engineering, particularly through its ability to precisely manipulate fluids and cells at microscopic scales. Microfluidic biomaterials, a cutting-edge interdisciplinary field integrating microfluidic technology with biomaterials science, are revolutionizing biomedical research. This review focuses on the functional design and fabrication of organ-on-a-chip (OoAC) platforms via 3D bioprinting, explores the applications of biomaterials in drug delivery, cell culture, and tissue engineering, and evaluates the potential of microfluidic systems in advancing personalized healthcare. We systematically analyze the evolution of microfluidic materials—from silicon and glass to polymers and paper—and highlight the advantages of 3D bioprinting over traditional fabrication methods. Currently, despite significant advances in microfluidics in medicine, challenges in scalability, stability, and clinical translation remain. The future of microfluidic biomaterials will depend on combining 3D bioprinting with dynamic functional design, developing hybrid strategies that combine traditional molds with bio-printed structures, and using artificial intelligence to monitor drug delivery or tissue response in real time. We believe that interdisciplinary collaborations between materials science, micromachining, and clinical medicine will accelerate the translation of organ-on-a-chip platforms into personalized therapies and high-throughput drug screening tools. Full article

In this paper, we explore the use of chip-scale blown glass microbubble structures for MEMS packaging applications. Specifically, we demonstrate the efficacy of this method of packaging for the improvement of the lifetime of a ferrofluid-based magnetoviscous magnetometer. We have previously reported on the novel concept of a ferrofluid based magnetometer in which the viscoelastic response of a ferrofluid interfacial layer on a high frequency shear wave quartz resonator is sensitively monitored as a function of applied magnetic field. The quantification of the magnetic field is accomplished by monitoring the at-resonance admittance characteristics of the ferrofluid-loaded resonator. While the proof-of-concept measurements of the device have been successfully made, under open conditions, the evaporation of the carrier fluid of the ferrofluid continuously changes its viscoelastic properties and compromises the longevity of the magnetometer. To prevent the evaporation of the ferrofluid, here, we seal the ferrofluid on top of the micromachined quartz resonator within a blown glass hemispherical microbubble attached to it using epoxy. The magnetometer design used a bowtie-shaped thin film Metglas (Fe₈₅B₅Si₁₀) magnetic flux concentrator on the resonator chip. A four-times smaller noise equivalent, a magnetic field of 600 nT/√Hz at 0.5 Hz was obtained for the magnetometer using the Metglas flux concentrator. The ferrofluid-based magnetometer is capable of sensing magnetic fields up to a modulation frequency of 40 Hz. Compared with the unsealed ferrofluid device, the lifetime of the glass microbubble integrated chip packaged device improved significantly from only a few hours to over 50 days and continued. Full article

Electric discharge machining (EDM) stands out for its ability to perform no-contact machining of materials with desired forms by multi-pulse discharges. In this investigation, the machinability of drilling on Ti₅₆Zr₁₈Cu₁₂, metallic glass, for micro-hole is investigated with renewable dielectrics in the EDM process. Machinability is investigated by examining performance indicators including material removal rate (MRR), overcut, edge deviation, and energy efficiency per volume (EEV) in relation to the process parameters, such as electrical and non-electrical parameters. The edges of the drilled holes are examined to investigate the micro-structural changes that occur in metallic glass as a result of micro-machining. The experimental results show that the maximal value of MRR of 0.0103 mm³/min is achieved when the pulse-on time of 30 μs and sunflower oil renewable dielectric is selected, and the minimum overcut and edge deviation of micro-hole drilling in Ti₅₆Zr₁₈Cu₁₂ is 39.99 and 9.41 μm, respectively. Minimum overcut and edge deviation are obtained for colza oil, optimized by 38% and 70%, respectively, over the worst-case conditions. Multi-objective optimization on the basis of ratio analysis (MOORA) results in a 70% reduction in energy consumption of EEV compared to the conventional paraffin media process. In addition, a range of pulse-on time, pulse duty cycle, and renewable dielectric are identified using the MOORA technique while EDM drilling in metallic glass Ti₅₆Zr₁₈Cu₁₂. Full article

This paper presents a novel approach to fabricate substrate integrated waveguides (SIWs) on glass substrates with tin (Sn) through glass vias (TGVs) tailored for millimeter-wave applications. The fabrication process employs a custom-designed vacuum suctioning system to rapidly fill precise TGV holes in the glass substrate, which are formed by wafer-level glass reflow micromachining techniques with molten tin in a minute. This method offers a very fast and cost-effective alternative for complete via filling without voids compared to the conventional metallization techniques such as electroplating or sputtering. An SIW with a 3-dB cutoff frequency of 17.2 GHz was fabricated using the proposed process. The fabricated SIW shows an average insertion loss of 1.65 ± 0.54 dB across the 20–35 GHz range. These results highlight the potential of glass substrates with tin TGVs for fabricating millimeter-wave devices. Full article

This paper reports the design, fabrication, and characterization of a MEMS capacitive accelerometer with an asymmetrical comb finger arrangement. By optimizing the ratio of the gaps of a rotor finger to its two adjacent stator fingers, the sensitivity of the accelerometer is maximized for the same comb finger area. With the fingers’ length, width, and depth at 120 μm, 4 μm, and 45 μm, respectively, the optimized finger gap ratio is 2.5. The area of the proof mass is 750 μm × 560 μm, which leads to a theoretical thermomechanical noise of 9 μg/√Hz. The accelerometer has been fabricated using a modified silicon-on-glass (SOG) process, in which a groove is pre-etched into the glass to hold the metal electrode. This SOG process greatly improves the silicon-to-glass bonding yield. The measurement results show that the resonant frequency of the accelerometer is about 2.05 kHz, the noise floor is 28 μg/√Hz, and the nonlinearity is less than 0.5%. Full article

In this study, based on the principle of grating interferometer-based acoustic sensors, design guidelines for the grating interferometric module were obtained and analyzed considering various factors in order to obtain high sensitivity, and a glass-based grating interference component and its acoustic sensor device were developed. The key parameters of the grating interference structure were extracted, and their effects on the acoustic response sensitivity were quantified for multiple mechanisms. For the development of the acoustic sensor, the grating-on-convex-platform structure and the micromachining processes of the glass-based components were designed and developed. The developed acoustic sensor samples achieved high sensitivity. In particular, the sample suitable for low-frequency application obtained a sensitivity of 0.776 V/Pa @ 1 kHz, and the spectrum of its sensitivity was flat from 50 Hz to 8 Hz with a deviation less than 1.5 dB and a sensitivity of 0.408 V/Pa @ 20 Hz. Full article

The abrasive waterjet machining process was introduced in the 1980s as a new cutting tool; the process has the ability to cut almost any material. Currently, the AWJ process is used in many world-class factories, producing parts for use in daily life. A description of this process and its influencing parameters are first presented in this paper, along with process models for the AWJ tool itself and also for the jet–material interaction. The AWJ material removal process occurs through the high-velocity impact of abrasive particles, whose tips micromachine the material at the microscopic scale, with no thermal or mechanical adverse effects. The macro-characteristics of the cut surface, such as its taper, trailback, and waviness, are discussed, along with methods of improving the geometrical accuracy of the cut parts using these attributes. For example, dynamic angular compensation is used to correct for the taper and undercut in shape cutting. The surface finish is controlled by the cutting speed, hydraulic, and abrasive parameters using software and process models built into the controllers of CNC machines. In addition to shape cutting, edge trimming is presented, with a focus on the carbon fiber composites used in aircraft and automotive structures, where special AWJ tools and manipulators are used. Examples of the precision cutting of microelectronic and solar cell parts are discussed to describe the special techniques that are used, such as machine vision and vacuum-assist, which have been found to be essential to the integrity and accuracy of cut parts. The use of the AWJ machining process was extended to other applications, such as drilling, boring, milling, turning, and surface modification, which are presented in this paper as actual industrial applications. To demonstrate the versatility of the AWJ machining process, the data in this paper were selected to cover a wide range of materials, such as metal, glass, composites, and ceramics, and also a wide range of thicknesses, from 1 mm to 600 mm. The trends of Industry 4.0 and 5.0, AI, and IoT are also presented. Full article

This paper presents a micromachined thermal convective accelerometer with low power and high reliability. This accelerometer comprises a heater and two thermistors. The central heater elevates the temperature of the chip above ambient levels while the symmetrically arranged thermistors monitor the temperature differentials induced by acceleration. The heater and thermistors are fabricated on a glass substrate using a standard micro-electromechanical systems (MEMS) process flow, and the fabricated sensor is installed on a rotation platform and a shaking table experimental setup to perform the experiment. The results indicate that the sensor has the capability to measure accelerations surpassing 80 m/s², with an approximate linear sensitivity of 110.69 mV/g. This proposed thermal convective accelerometer offers promising potential for various applications requiring precise acceleration measurements in environments where low power consumption and high reliability are paramount. Full article

MEMS capacitive pressure sensors have proven to be more reliable in terms of temperature drift and long-term stability when compared to MEMS piezoresistive pressure sensors. In this study, a MEMS capacitive pressure sensor using micromachined technology has been designed and fabricated. As the movable electrode, a silicon membrane is used, while the fixed electrode is a gold metal film on a glass substrate. There is no deformation of the silicon membrane when the pressure is equal on both sides. As a result of the pressure of 0 kPa applied to the silicon membrane, a capacitance exists between it and the metal electrode. Differences in pressure on both sides of the silicon membrane will cause the membrane to deform. Silicon membranes deform due to pressure differences, which affect the capacitance between metal electrodes and silicon membranes. MEMS capacitive pressure sensors benefit from the superior mechanical properties of silicon material compared to metal-based sensors. Capacitive MEMS sensors are more desirable for applications requiring high performance and stability as compared to metal pressure sensors. This device is suited to measuring blood pressure with a measurement range of 0–45 kPa. When applied pressure was 0 kPa, the measurement capacitance was 3.61 pF, and when 45 kPa was applied, it was 7.19 pF. Full article

Half-bridge silicon strain gauges are widely used in the fabrication of diaphragm-type high-pressure sensors, but in some applications, they suffer from low output sensitivity because of mounting position constraints. Through a special design and fabrication approach, a new half-bridge silicon strain gauge comprising one arc gauge responding to tangential strain and another linear gauge measuring radial strain was developed using Silicon-on-Glass (SiOG) substrate technology. The tangential gauge consists of grid patterns, such as the reciprocating arc of silicon piezoresistors on a thin glass substrate. When two half-bridges are connected to form a full bridge with arc-shaped gauges that respond to tangential strain, they have the advantage of providing much higher output sensitivity than a conventional half-bridge. Pressure sensors tested under pressure ranging from 0 to 50 bar at five different temperatures indicate a linear output with a typical sensitivity of approximately 16 mV/V/bar, a maximum zero shift of 0.05% FS, and a span shift of 0.03% FS. The higher output level of pressure sensing gauges will provide greater signal strength, thus maintaining a better signal-to-noise ratio than conventional pressure sensors. The offset and span shift curves are quite linear across the operating temperature range, giving the end user the advantage of using very simple algorithms for temperature compensation of offset and span shift. Full article

In this paper, an ultrasonic target detection system based on Piezoelectric Micromachined Ultrasonic Transducers (PMUTs) is proposed, which consists of the PMUTs based ultrasonic sensor and the sensor system. Two pieces of 3 × 3 PMUTs arrays with the resonant frequency of 115 kHz are used as transmitter and receiver of the PMUTs-based ultrasonic sensor. Then, the sensor system can calculate the target’s position through the signal received by the above receiver. The static and dynamic performance of the proposed prototype system are characterized on black, white, and transparent targets. The experiment results demonstrated that the proposed system can detect targets of different colors, transparencies, and motion states. In the static experiments, the static location errors of the proposed system in the range of 200 mm to 320 mm are 0.51 mm, 0.50 mm and 0.53 mm, whereas the errors of a commercial laser sensor are 2.89 mm, 0.62 mm, and N\A. In the dynamic experiments, the experimental materials are the targets with thicknesses of 1 mm, 1.5 mm, 2 mm and 2.5 mm, respectively. The proposed system can detect the above targets with a maximum detection error of 4.00%. Meanwhile, the minimum resolution of the proposed system is about 0.5 mm. Finally, in the comprehensive experiments, the proposed system successfully guides a robotic manipulator to realize the detecting, grasping, and moving of a transparent target with 1 mm. This ultrasonic target detection system has demonstrated a cost-effective method to detect targets, especially transparent targets, which can be widely used in the detection and transfer of glass substrates in automated production lines. Full article

Currently, silicon-strain-gauge-based diaphragm pressure sensors use four single-gauge chips for high-output sensitivity. However, the four-single-gauge configuration increases the number of glass frit bonds and the number of aluminum wire bonds, reducing the long-term stability, reliability, and yield of the diaphragm pressure sensor. In this study, a new design of general-purpose silicon strain gauges was developed to improve the sensor output voltage while reducing the number of bonds. The new gauges consist grid patterns with a reciprocating arc of silicon piezoresistors on a thin glass backing. The gauges make handling easier in the bonding process due to the use of thin glass for the gauge backing. The pressure sensors were tested under pressure ranging from 0 to 50 bar at five different temperatures, with a linear output with a typical sensitivity of approximately 16 mV/V/bar and an offset shift of –6 mV to 2 mV. The new approach also opens the possibility to extend arc strain gauges to half-bridge and full-bridge configurations to further reduce the number of glass frit and Al wire bonds in the diaphragm pressure sensor. Full article

A millimeter-wave substrate-integrated waveguide (SIW) was firstly demonstrated using the micromachining of photoetchable glass (PEG) for 5G applications. A PEG substrate was used as a dielectric material of the SIW, and its photoetchable properties were used to fabricate through glass via (TGV) holes. Instead of the conventional metallic through glass via (TGV) array structures that are typically used for the SIW, two continuous empty TGV holes with metallized sidewalls connecting the top metal layer to the bottom ground plane were used as waveguide walls. The proposed TGV walls were fabricated by using optical exposure, heat development and anisotropic HF (hydrofluoric acid) etching of the PEG substrate, followed by a metal sputtering technique. The SIW was fed by microstrip lines connected to the waveguide through tapered microstrip-to-waveguide transitions. The top metal layer, including these feedlines and transitions, was fabricated by selective metal sputtering through a silicon shadow mask, which was prefabricated by a silicon deep-reactive ion-etching (DRIE) technique. The developed PEG-based process provides a relatively simple, wafer-level manufacturing method to fabricate the SIW in a low-cost glass dielectric substrate, without the formation of individual of TGV holes, complex time-consuming TGV filling processes and repeated photolithographic steps. The fabricated SIW had a dimension of 6 × 10 × 0.42 mm³ and showed an average insertion loss of 2.53 ± 0.55 dB in the Ka-band frequency range from 26.5 GHz to 40 GHz, with a return loss better than 13.86 dB. The proposed process could be used not only for SIW-based devices, but also for various millimeter-wave applications where a glass substrate with TGV structures is required. Full article

Ultrafast laser ablation is widely used as a versatile method for accurate micro-machining of polymers, glasses and metals for a variety of industrial and biomedical applications. We report on the use of a novel process parameter, the modulation of the laser pulse energy during the multi-scan texturing of surfaces. We show that this new and straightforward control method allows us to attain higher and lower roughness ($R_a$) values than the conventional constant pulse energy irradiation sequence. This new multi-scanning laser ablation strategy was conducted on metals that are commonly used in the biomedical industry, such as stainless steel, titanium, brass and silver samples, using a linear (increasing or decreasing) gradient of pulse energy, i.e., varying the pulse energy across successive laser scans. The effects of ablation were studied in terms of roughness, developed interfacial area ratio, skewness and ablation efficiency of the processed surfaces. Significantly, the investigation has shown a global trend for all samples that the roughness is minimum when a decreasing energy pulse sequence is employed, i.e., the irradiation sequence ends up with the applied laser fluences close to threshold laser fluences and is maximum with increasing energy distribution. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) analysis on single craters with the three different energy deposition conditions revealed a chaotic and random material redistribution in the cases of uniform and increasing energy distributions and the presence of regular laser-induced periodic surface structures (LIPSS) at the bottom of the ablation region in the case of decreasing energy distribution. It is also shown that the ablation efficiency of the ablated surfaces does not significantly change between the three cases. Therefore, this novel energy control strategy permits the control of the roughness of the processed surfaces without losing the ablation efficiency. Full article