An enhanced-performance multisensing progressive cellular μGC: design advances and blind test results.

Many environmental, industrial, and security applications demand in-field analysis of chemical vapors. Whereas microscale gas chromatographs (µGCs) are promising candidates, reliable in-field chemical analysis particularly demands repeatability, humidity tolerance, and in-field reference. Using a µGC with substantial monolithic integration (of preconcentrators, separation columns, and capacitive and photoionization detectors), this paper reports chip-level and system-level advancements towards reliable chemical analysis.

An ingestible device for automated sampling and location tracing in gastrointestinal tract.

Fluids sampled from the gastrointestinal (GI) tract are of interest for evaluating the bioequivalence of oral medications, and more generally for evaluating GI-related diseases, and for profiling the individual gut microbiome. Existing options for capturing multiple fluid samples from specific locations in the GI tract are limited and invasive, particularly for the small intestine. Here, we report the development of an ingestible capsule for the collection of multiple fluid samples along the GI tract; we additionally report the use of data from sensors within the capsule to determine the sampling regions.

A microsystem for in vivo wireless monitoring of plastic biliary stents using magnetoelastic sensors.

With an interest in monitoring the patency of stents that are used to treat strictures in the bile duct, this paper reports the investigation of a wireless sensing system to interrogate a microsensor integrated into the stent. The microsensor is comprised of a 28-μm-thick magnetoelastic foil with 8.25-mm length and 1-mm width.

Control Software Design for a Multisensing Multicellular Microscale Gas Chromatography System.

Microscale gas chromatography (μGC) systems are miniaturized instruments that typically incorporate one or several microfabricated fluidic elements; such systems are generally well suited for the automated sampling and analysis of gas-phase chemicals. Advanced μGC systems may incorporate more than 15 elements and operate these elements in different coordinated sequences to execute complex operations. In particular, the control software must manage the sampling and analysis operations of the μGC system in a time-sensitive manner; while operating multiple control loops, it must also manage error conditions, data acquisition, and user interactions when necessary.

Automatic peak detection algorithm based on continuous wavelet transform for complex chromatograms from multi-detector micro-scale gas chromatographs.

Peak detection for chromatograms, including the detection of peak retention times, peak start locations, and peak end locations, is an important processing step for extracting peak information that is used for chemical recognition. Compared to benchtop gas chromatographs, the chromatograms generated by microscale gas chromatographs (µGCs) often contain higher noise levels, peak overlap, peak asymmetry, and both positive and negative chromatographic peaks, increasing the challenges for peak detection. This paper reports an automatic peak detection algorithm based on continuous wavelet transform (CWT) for chromatograms generated by multi-detector µGCs.

Passive Wireless Pressure Gradient Measurement System for Fluid Flow Analysis.

Using distributed MEMS pressure sensors to measure small flow rates in high resistance fluidic channels is fraught with challenges far beyond the performance of the pressure sensing element. In a typical core-flood experiment, which may last several months, flow-induced pressure gradients are generated in porous rock core samples wrapped in a polymer sheath. Measuring these pressure gradients along the flow path requires high resolution pressure measurement while contending with difficult test conditions such as large bias pressures (up to 20 bar) and temperatures (up to 125 °C), as well as the presence of corrosive fluids.

Highly Integrated μGC Based on a Multisensing Progressive Cellular Architecture with a Valveless Sample Inlet.

Microscale gas chromatographs (μGCs) promise in-field analysis of volatile organic compounds (VOCs) in environmental and industrial monitoring, healthcare, and homeland security applications. As a step toward addressing challenges with performance and manufacturability, this study reports a highly integrated monolithic chip implementing a multisensing progressive cellular architecture. This architecture incorporates three μGC cells that are customized for different ranges of analyte volatility; each cell includes a preconcentrator and separation column, two complementary capacitive detectors, and a photoionization detector (PID).

Progressive Cellular Architecture in Microscale Gas Chromatography for Broad Chemical Analyses.

Gas chromatography is widely used to identify and quantify volatile organic compounds for applications ranging from environmental monitoring to homeland security. We investigate a new architecture for microfabricated gas chromatography systems that can significantly improve the range, speed, and efficiency of such systems. By using a cellular approach, it performs a partial separation of analytes even as the sampling is being performed.

A Bidirectional Knudsen Pump with a 3D-Printed Thermal Management Platform.

This paper reports on a bidirectional Knudsen pump (KP) with a 3D-printed thermal management platform; the pump is intended principally for microscale gas chromatography applications. Knudsen pumps utilize thermal transpiration, where non-viscous flow is created against a temperature gradient; no moving parts are necessary. Here, a specialized design leverages 3D direct metal laser sintering and provides thermal management that minimizes loss from a joule heater located on the outlet side of KP, while maintaining convective cooling on the inlet side.

Encapsulation Approaches for In-Stent Wireless Magnetoelastic Sensors.

Wireless magnetoelastic sensors offer significant potential for measuring the accumulation of biomass within stents - enabling early detection prior to stent occlusion - but the encapsulation of these sensors remains a critical challenge. The encapsulation must allow the sensors to navigate the curvature and accommodate the contact forces imparted during and after the implantation procedure, while also leaving the sensor open to mechanical interaction with the biomass during the extended period of deployment. This paper is focused on the encapsulation of ribbon-like magnetoelastic sensors (12.

Autonomous Microsystems for Downhole Applications: Design Challenges, Current State, and Initial Test Results.

This paper describes two platforms for autonomous sensing microsystems that are intended for deployment in chemically corrosive environments at elevated temperatures and pressures. Following the deployment period, the microsystems are retrieved, recharged, and interrogated wirelessly at close proximity. The first platform is the Michigan Micro Mote for High Temperature (M³HT), a chip stack 2.

Wireless Strain Measurement with a Micromachined Magnetoelastic Resonator Using Ringdown Frequency Locking.

Resonant magnetoelastic devices are widely used as anti-theft tags and are also being investigated for a range of sensing applications. The vast majority of magnetoelastic devices are operated at resonance, and rely upon an external interface to wirelessly detect the resonant frequency, and other characteristics. For micromachined devices, this detection method must accommodate diminished signal strength and elevated resonant frequencies.

A fully electronic microfabricated gas chromatograph with complementary capacitive detectors for indoor pollutants.

This paper reports a complete micro gas chromatography (μGC) system in which all the components are lithographically microfabricated and electronically interfaced. The components include a bi-directional Knudsen pump, a preconcentrator, separation columns and a pair of capacitive gas detectors; together, these form the system. All the fluidic components of the system are fabricated by a common three-mask lithographic process.

In vivo and in situ evaluation of a wireless magnetoelastic sensor array for plastic biliary stent monitoring.

This paper presents the in vivo and in situ evaluation of a system that wirelessly monitors the accumulation of biliary sludge in a plastic biliary stent. The sensing element, located within the stent, is a passive array of magnetoelastic resonators that is queried by a wireless electromagnetic signal. The in vivo and in situ testing uses commercially-available plastic biliary stents, each enhanced with an array of ribbon sensors (formed from Metglas™ 2826 MB).

Compact, power-efficient architectures using microvalves and microsensors, for intrathecal, insulin, and other drug delivery systems.

This paper describes a valve-regulated architecture, for intrathecal, insulin and other drug delivery systems, that offers high performance and volume efficiency through the use of micromachined components. Multi-drug protocols can be accommodated by using a valve manifold to modulate and mix drug flows from individual reservoirs. A piezoelectrically-actuated silicon microvalve with embedded pressure sensors is used to regulate dosing by throttling flow from a mechanically-pressurized reservoir.

Adaptive two-dimensional microgas chromatography.

We proposed and investigated a novel adaptive two-dimensional (2-D) microgas chromatography system, which consists of one 1st-dimensional column, multiple parallel 2nd-dimensional columns, and a decision-making module. The decision-making module, installed between the 1st- and 2nd-dimensional columns, normally comprises an on-column nondestructive vapor detector, a flow routing system, and a computer that monitors the detection signal from the detector and sends out the trigger signal to the flow routing system. During the operation, effluents from the 1st-dimensional column are first detected by the detector and, then, depending on the signal generated by the detector, routed to one of the 2nd-dimensional columns sequentially for further separation.

A biopsy tool with integrated piezoceramic elements for needle tract cauterization and cauterization monitoring.

This paper reports the feasibility of biopsy needle tract cauterization and cauterization monitoring using an embedded array of piezoceramic microheaters. Circular heaters of lead zirconate titanate (PZT-5A), with 200 μm diameter and 70-80 μm thickness, are fabricated using a batch mode micro ultrasonic machining process. These are then assembled into cavities in the walls of 20-gauge stainless steel needles and sealed with epoxy.

Demonstration of motionless Knudsen pump based micro-gas chromatography featuring micro-fabricated columns and on-column detectors.

This paper reports the investigation of a micro-gas chromatography (μGC) system that utilizes an array of miniaturized motionless Knudsen pumps (KPs) as well as microfabricated separation columns and optical detectors. A prototype system was built to achieve a flow rate of 1 mL min(-1) and 0.26 mL min(-1) for helium and dry air, respectively, when they were used as carrier gas.

Experimental evaluation of an adaptive Joule-Thomson cooling system including silicon-microfabricated heat exchanger and microvalve components.

This article reports the evaluation of a Joule-Thomson (JT) cooling system that combines two custom micromachined components-a Si/glass-stack recuperative heat exchanger and a piezoelectrically actuated expansion microvalve. With the microvalve controlling the flow rate, this system can modulate cooling to accommodate varying refrigeration loads. The perforated plate Si/glass heat exchanger is fabricated with a stack of alternating silicon plates and Pyrex glass spacers.

Note: A low leakage liquid seal for micromachined gas valves.

We report a method for addressing gas leakage in micromachined valves. The valves used for evaluating the proposed concept utilize a silicon valve seat that is bonded to a glass substrate and actuated by a piezoelectric stack, all of which are assembled within a ceramic package. The sealing method uses the capillary forces of a liquid sealant on the valve seat to reduce gas leakage below measurable limits.

A Si/Glass Bulk-Micromachined Cryogenic Heat Exchanger for High Heat Loads: Fabrication, Test, and Application Results.

This paper reports on a micromachined Si/glass stack recuperative heat exchanger with in situ temperature sensors. Numerous high-conductivity silicon plates with integrated platinum resistance temperature detectors (Pt RTDs) are stacked, alternating with low-conductivity Pyrex spacers. The device has a 1 x 1-cm(2) footprint and a length of up to 3.

In situ and ex vivo evaluation of a wireless magnetoelastic biliary stent monitoring system.

This paper presents the in situ and ex vivo evaluation of a system that wirelessly monitors the accumulation of intimal tissue and sludge in a biliary stent. The sensing element, located within the stent, is a magnetoelastic resonator that is queried by a wireless radio frequency signal. The in situ testing uses a commercially-available self-expanding biliary stent enhanced with a 1 mm x 25 mm magnetoelastic ribbon sensor (formed from Metglas 2605SA1).

A blood sampling microsystem for pharmacokinetic applications: design, fabrication, and initial results.

This paper describes a microsystem for automated blood sampling from laboratory mice used in pharmacokinetic studies. Intended to be mounted as a "backpack" on a mouse, it uses a microneedle, reservoir, and an actuator to instantaneously prick the animal for a time-point sample, eliminating the need for a tethered catheter with large dead volume. The blood is collected by capillary effect through a 31-33 gauge microneedle (250-210 microm OD) into a approximately 1 microL micromachined steel reservoir.

Hybrid micro-technologies for medical applications.

Medical applications have long provided an impetus for research in silicon-based microsystems. This paper explores micro-technologies that complement and extend conventional manufacturing approaches and applications. For example, lithographic microfabrication methods can be used to fabricate stents and integrated microsensors that can monitor lumen patency in cardiac and biliary applications.

Transdermal power transfer for recharging implanted drug delivery devices via the refill port.

This paper describes a system for transferring power across a transdermal needle into a smart refill port for recharging implantable drug delivery systems. The device uses a modified 26 gauge (0.46 mm outer diameter) Huber needle with multiple conductive elements designed to couple with mechanical springs in the septum of the refill port of a drug delivery device to form an electrical connection that can sustain the current required to recharge a battery during a reservoir refill session.