A cell culture well with integrated mechanical and optical stimulation is presented. This is achieved by combining dielectric elastomer soft actuators, also known as artificial muscles, and a varifocal micro-electromechanical mirror that couples light from an optical fiber and focuses it onto the transparent cell substrate. The device enables unprecedented control ofin vitrocell cultures by allowing the experimenter to tune and synchronize mechanical and optical stimuli, thereby enabling new experimental assays in optogenetics, fluorescent microscopy, or laser stimulation that include dynamic mechanical strain as a controlled input parameter.

Avian species have a long fossil history of altering vertebrate remains, including hominin. Some of the most forensically important taxa in the USA include New World vultures (Cathartidae), including turkey vultures (Cathartes aura) and black vultures (Coragyps atratus), crows (Corvidae), falcons (Falconidae), eagles and hawks (Accipitridae), and gulls (Laridae), although scavenging has been noted among smaller taxa, including songbirds (Passerines). The taphonomic effects caused by birds can include the reduction of soft tissue, which can be rapid due to the actions of some species, particularly vultures. While engaged in feeding, birds also may leave marks on soft tissue or bones from their beaks or talons that may indicate their involvement. Bird feeding also can cause significant dispersal of bones, which should be considered when planning recovery efforts.

Magnetic sensing is present in our everyday interactions with consumer electronics and demonstrates the potential for the measurement of extremely weak biomagnetic fields, such as those of the heart and brain. In this work, we leverage the many benefits of microelectromechanical system (MEMS) devices to fabricate a small, low-power, and inexpensive sensor whose resolution is in the range of biomagnetic fields. At present, biomagnetic fields are measured only by expensive mechanisms such as optical pumping and superconducting quantum interference devices (SQUIDs), suggesting a large opportunity for MEMS technology in this work. The prototype fabrication is achieved by assembling micro-objects, including a permanent micromagnet, onto a postrelease commercial MEMS accelerometer using a pick-and-place technique. With this system, we demonstrate a room-temperature MEMS magnetic gradiometer. In air, the sensor's response is linear, with a resolution of 1.1nTcm(-1), spans over 3 decades of dynamic range to 4.6 mu Tcm(-1), and is capable of off-resonance measurements at low frequencies. In a 1mTorr vacuum with 20dB magnetic shielding, the sensor achieves a 100pTcm(-1) resolution at resonance. This resolution represents a 30-fold improvement compared with that of MEMS magnetometer technology and a 1000-fold improvement compared with that of MEMS gradiometer technology. The sensor is capable of a small spatial resolution with a magnetic sensing element of 0.25mm along its sensitive axis, a >4-fold improvement compared with that of MEMS gradiometer technology. The calculated noise floor of this platform is 110fTcm(-1)Hz(-1/2), and thus, these devices hold promise for both magnetocardiography (MCG) and magnetoencephalography (MEG) applications. Magnetic sensing: Small, low-cost magnetic sensor with wide field strengthA small, low-power, inexpensive magnetic sensor has been developed in a commercially available platform with a resolution that is within the range of biomagnetic fields. Magnetic sensing is applied in everyday interactions with consumer electronics (such as for navigation) and has the potential to measure extremely weak biomagnetic fields (such as those of the heart and brain). Hitherto, biomagnetic fields have been measured only using expensive mechanisms. However, a team headed by Josh Javor at Boston University, USA has succeeded in applying the benefits of micro-electromechanical systems to fabricate a low-cost magnetic sensor in a small, versatile platform that can be easily integrated into consumer technology. We believe that their new technology has the potential to revolutionize magnetic sensing and offer considerable advantages in such areas as navigation, communication, and biomagnetic field mapping.

There is a world-wide push to create the next-generation all-optical transmission and switching technologies for exascale data centers. In this paper we focus on the switching fabrics. Many different types of 2D architectures are being explored including MEMS/waveguides and semiconductor optical amplifiers. However, these tend to suffer from high, path-dependent losses and crosstalk issues. The technologies with the best optical properties demonstrated to date in large fabrics (>100 ports) are 3D MEMS beam steering approaches. These have low average insertion losses and, equally important, a narrow loss distribution. However, 3D MEMS fabrics are generally dismissed from serious consideration for this application because of their slow switching speeds (∼few milliseconds) and high costs ($100/port). In this paper we show how novel feedforward open loop controls can solve both problems by improving MEMS switching speeds by two orders of magnitude and costs by a factor of three. With these improvements in hand, we believe 3D MEMS fabrics can become the technology of choice for data centers.

We present electrothermal microelectromechanical (MEMS) actuators as a practical platform for straining 2D materials. The advantages of the electrothermal actuator is its high output force and displacement for low input voltage, but its drawback is that it is actuated by generating high amounts of heat. It is crucial to mitigate the high temperatures generated during actuation for reliable 2D material strain device implementation. Here, we implement a chevron actuator design that incorporates a thermal isolation stage in order to avoid heating the 2D material from the high temperatures generated during the actuation. By comparing experiment and simulation, we ensure our design does not compromise output displacement, while keeping the 2D material strain device stage cool. We also provide a simple analytical model useful for quickly evaluating different thermal isolation stage designs.

In this paper, we discuss a novel, mixed mode 3D XYZ scanner built within a single foundry process. The device has a large range of motion in X, Y and Z (14.0 μm in X,Y and 97.9 μm in Z) and can also rotate about two axes (7.4°), making it a 5 degree of freedom scanner. Vertical actuation can be accomplished with both thermal actuators, which have a larger range of motion, and capacitive actuators, which are faster, responding fully up to 3.2 kHz. Although it is useful for many applications, including scanning probe microscopy, micrometer scale optical microscopy, and manipulation of biological objects, the device was designed to be a 3D scanner for spray-painting atoms upon a surface with nanoscale precision and resolution for nanofabrication. Demonstrating the ability to combine the device with other complicated MEMS systems, it is integrated with an XY scanner designed to serve as a shutter to control the flow of atoms. The full system has 7 degrees of freedom and 12 actuation motors, and because it is built in a low cost commercial foundry with a robust, stable process, it is easy and inexpensive to fabricate multiple copies or integrate into other complicated systems, making a system of systems.

In this paper, we discuss the use of pulse width modulation (PWM) to control analog MEMS devices. We achieve a precise linear analog control of MEMS by applying PWM signal with a frequency well above the system's mechanical natural frequency. We first demonstrate this using a parallel plate actuator and comb-drive, and then extend the technique to control a commercial deformable mirror. Such an approach allows the system designer to replace expensive drive electronics such as the high precision DACs and high voltage, linear amplifiers with a simple on-off switch. The advancements in the electronics industry tend to make precise timing cheaper and faster; our approach exploits these long-term trends to create low-cost control circuits. We also show how PWM control can linearize the positional response of the devices, where typically the position would depend quadratically on the applied analog voltage.

Beam steering is essential for a variety of optical applications such as communication, LIDAR, and imaging. Microelectromechanical system (MEMS) mirrors are an effective method of achieving modest speeds and angular range at low cost. Typically there are a number of tradeoffs considered when designing a tip-tilt mirror, such as tilt angle and speed. For example, many mirrors are designed to scan at their resonant frequency to achieve large angles. This is effective for a scanning mode; however, this makes the device slow and ineffective as a galvo (quasi-static). Here, we present a magnetic MEMS mirror with extreme quasi-static mechanical tilt angles of ±60° (±120° optical) about two rotation axes. This micromirror enables full hemispheric optical coverage without compromising speed; settling in 4.5 ms using advanced drive techniques. This mirror will enable new applications for MEMS micromirrors previously thought impossible due to their limited angular range and speed.

There is a world-wide push to create the next generation all-optical transmission and switching technologies for exascale data centers. In this paper we focus on the switching fabrics. Many different types of 2D architectures are being explored including MEMS/waveguides and semiconductor optical amplifiers. However, these tend to suffer from high, path dependent losses and crosstalk issues. The technologies with the best optical properties demonstrated to date in large fabrics (>100 ports) are 3D MEMS beam steering approaches. These have low average insertion losses, and equally important, a narrow loss distribution. However, 3D MEMS fabrics are generally dismissed from serious consideration for this application because of their slow switching speeds (~few milliseconds) and costs ($100/port). In this paper we show how novel feedforward open loop controls can solve both problems by improving switching speeds by two orders of magnitude and costs by one order of magnitude. With these improvements in hand, we believe 3D MEMS fabrics can become the technology of choice for data centers.

Magnetic sensing is present in our everyday interactions with consumer electronics, and also demonstrates potential for measurement of extremely weak biomagnetic fields, such as those of the heart and brain. In this work, we leverage the many benefits of the micro-electromechanical systems (MEMS) devices to fabricate a small, low power, inexpensive sensor whose resolution is in the range of weak biomagnetic fields. The sensor works at room temperature, and is suitable for consumer electronics integration. At present, such biomagnetic fields can only be measured by expensive mechanisms such as optical pumping and superconducting quantum interference devices (SQUIDs). Thus, our sensor suggests the opening of a large phase space for medical and consumer applications. The prototype fabrication is achieved by assembling micro-objects, including a permanent micromagnet, onto a post-release commercial MEMS accelerometer. With this system, we demonstrate a room temperature MEMS magnetometer, whose design is only sensitive to gradient magnetic fields and is generally insensitive to the Earth's uniform field. In air, the sensor's response is linear with a resolution of 1.1 nT cm-1 and spans over 3 decades of dynamic range to 4.6 {\mu}T cm-1. In 1 mTorr vacuum with 20 dB magnetic shielding, the sensor achieved 100 pT cm-1 resolution at resonance. The theoretical floor of this design is 110 fT cm-1 Hz-1/2 with a resolution of 13 fT cm-1, thus these devices hold promise for both magnetocardiography (MCG) and magnetoencephalography (MEG) applications.

Record high sensitivity of 90dB is achieved in a chip-scale SS-OCT system. A PLC interferometer, on-chip balanced diode pair, and ball lens coupled MEMS mirror form an ultra-compact optical engine for 3D imaging.

Microelectromechanical systems (MEMS) provide engineers with a rich palette of technical solutions to a wide range of actuation and sensing challenges. MEMS devices are low cost, easily integrated with sense and drive electronics, are robust, and can be designed to respond to electrical, mechanical, or chemical stimuli. Because they are mechanical, MEMS devices suffer from being relatively slow in comparison with purely electronic devices. However, it has been shown that by using feedforward drives developed using controls theory approaches, it is possible to significantly improve the step and settle time of MEMS actuators. This paper uses this technique to demonstrate the use of pulse width modulation to linearly drive MEMS. Furthermore, it demonstrates an overdrive method capable of improving the step and settle time of a commercial MEMS device by a factor of 1500. The approach is general and can be used for a wide range of devices and actuation methods, such as electrostatic, electromagnetic, and thermal actuation. This provides engineers a simple method to design high Q MEMS devices with sub-millisecond response times, opening the phase space for more micromechanical solutions.

The role of small scavengers (typically birds and small mammals) of large vertebrate remains in terrestrial environments is an under-researched aspect of forensic taphonomy. The present research examined the role of small scavengers in a wooded environment in Massachusetts. A sample of fresh, mostly defleshed pig (Sus scrofa) femora was placed in heavy mesh wire cages that restricted access by the largest scavengers but allowed full access by smaller scavengers. The bones were monitored with game cameras for a four-month period from 8 June through 7 October 2016, and bones were replaced frequently. A minimum of 8 bird and 10 mammalian taxa were detected scavenging the remains, including multiple Passerines, turkey vulture (Cathartes aura), mustelids, raccoon (Procyon lotor), Virginia opossum (Didelphis virginiana), and rodents including eastern gray squirrel (Sciurus carolinensis) and chipmunk (Tamias striatus). Gnawing damage to bone was accrued by fisher (Martes pennanti), but the remaining scavengers only consumed adhering soft tissue. The small scavenger guild in this region is diverse and has a high potential for involvement in the scavenging of human skeletal remains in exposed terrestrial environments.KEYWORDS: forensic anthropology, forensic taphonomy, scavenger guild, scavenging, bone gnawing, Massachusetts

Determining the depositional environment and the postmortem alterations to a set of remains are necessary aspects of a forensic investigation to explain the circumstances surrounding the death of an individual. The present study examines organic staining as a method for reconstructing the depositional environment of skeletal remains and the taphonomic agents with which they came into contact. Organic staining results largely from tannins leaching from plant materials and therefore can be seen on bone deposited in wooden coffin environments or on terrestrial surfaces. The present study examines the hypothesis that the degree of staining observed on skeletal elements would increase as the length of exposure to the organic matter increased and that different plant materials and environments would leave different patterns or colorations of staining. The sample consisted of 165 pig (Sus scrofa) femora divided into four groups exposed to differing experimental conditions, including burial in direct contact with soil or burial in a simulated coffin environment, immersion in water with wood samples, and surface deposition with plant matter contact. The bones were removed once a month from their experimental environments and the level of staining was recorded qualitatively using the Munsell Soil Color Chart. In all of the experimental environments, staining was present after two months of exposure, and the color darkened across the bone surface with each episode of data collection. The results from the present study indicate that staining can manifest on bone within a relatively short time frame once skeletonization occurs and a variety of colorations or patterns of staining can manifest based on the plant material. The present research also demonstrates the potential of organic staining to aid in estimations of the postmortem interval as well as a depositional environmental reconstruction through plant species identification.

MEMS mirrors are currently used in many applications to steer beams of light. An area of continued research is developing mirrors with varifocal capability that allows the beam to be shaped and focused. In this work, we study the varifocal capability of a 380 μm diameter, thermally actuated MEMS mirror with a ± 40° tip-tilt angle and a radius of curvature between -0.48 mm to 20.5 mm. Light is coupled to the mirror via a single mode optical fiber, similar to an indoor optical wireless communication architecture. The performance of the mirror is characterized with respect to (1) the profile of the reflected beam as the mirror deforms and (2) the mirror's impact when integrated into an optical communication system. We found that the mirror can focus light to a beam with a 0.18° half-angle divergence. Additionally, the ability to change the shape of fiberized light from a wide to narrow beam provides an unmatched level of dynamic control and significantly improves the bit error rate in an optical communication system.

Micro/nanoelectromechanical systems (MEMS/NEMS) provide the engineer with a powerful set of solutions to a wide variety of technical challenges. However, because they are mechanical systems, response times can be a limitation. In some situations, advanced engineered drive techniques can improve response times by as much as a thousand fold, significantly opening up the application space for MEMS/NEMS solutions.