Despite the urgent need to integrate sustainability throughout the engineering curriculum, most faculty have little to no training or confidence in doing so. We report on a 4-day pilot faculty workshop delivered in January 2023 by an interdisciplinary group of faculty at a large mid-Atlantic R1 university designed to help engineering instructors do this. After substantial effort to create a mutual understanding around the diverse approaches we as faculty bring from our respective disciplines, we decided to follow a “spiral model” for the workshop, in which an initial introduction of a concept, skill, or consideration was later revisited, sometimes multiple times, to deepen the conversation in each iteration and to show their interconnectedness. In addition to introducing sustainability learning outcomes (LOs), including LOs for diversity, equity, and inclusion (DEI), we demonstrated tools such as life cycle assessment and sociotechnical integration, considered new ways to think about assessment, and shared information about various sustainability topics. Emphasis was placed on the development of students’ critical thinking, socio-technical systems thinking, and sense of agency. Demonstrations were integrated as a method of teaching, and mental models were introduced. Examples were shared by faculty who had already begun to incorporate sustainability concepts into their courses. During the workshop, the participants planned concrete changes to their own courses and discussed changing the curriculum across the 4 years of the undergraduate experience.

This paper discusses the piloting of a new undergraduate course, Entrepreneurial Design Realization, in the Engineering School at University of Maryland (UMD) over three semesters. This course is specifically aimed at tackling socially or environmentally responsible projects that include real deliverables that go out into the public domain. The course was originally conceived as a capstone followup where top viable projects with positive impact could be followed up with real opportunities for implementation. The course was developed as a part of a broader effort from the newly formed Environmentally and Socially Responsible Engineering group which aims to develop empowered, socially and environmentally responsible engineering graduates. The student empowerment and agency arises from opportunities for real do-ing as a part of the undergraduate educational experience, with the ultimate goal of a product or service reaching the public domain. This intrinsically necessitates multidisciplinary approaches that merge engineering with other disciplines. Social entrepreneurial aspects are inherent to all of the projects, with a necessity to demonstrate positive impact in order to pitch for funding or support. Three projects have been tackled: a commercial oyster farming product with a prototype delivered to an affiliate research institution, an engineering outreach kit redesign for K-12 with over 4000 units delivered, and a therapy playground co-developed with the Department of Hearing and Speech Sciences in another college. Discussed are the lessons learned in the process so far. These include: failures to recruit non-engineering students despite partnerships across campus, challenges in selecting projects that fit within the framework of an academic course structure, student successes and challenges, the existing funding structure and the challenges of developing this aspect within the course, and finally future directions and plans to continue the effort.

We report on a faculty workshop delivered in January 2023 by an in-terdisciplinary group of faculty members designed to help engineer-ing instructors integrate sustainability concepts into their courses. Our aim was to equip faculty members with skills and information to re-tool – in tiny or grand ways – their courses. The schedule includ-ed not only the teaching of specific skills (for example, how to create a stakeholder map or perform a design-level life cycle assessment), but also examples from faculty who had already made changes, demonstrations of pedagogical techniques, discussions of what changes could be made holistically across the 4 years of the under-graduate experience, and contextual information (such as ecological economics). A “spiral” model of organization was used, in which in-itial introductions were made across the range of these areas and then followed up several times, allowing time for each to be consid-ered and to be seen in relation to the others, since all are interrelated. This paper presents the lessons learned from this effort, participant’s planned changes to courses, and next steps.

A handheld fluorometer for detecting blue/green fluorescence from small Stokes shift fluorophores is presented in this paper. Two novel techniques have been introduced to emulate far-field operation while operating in the near field. A sensitivity of 26 (seconds per decade of dilution) and a resolution of 0.01 (concentration units) was achieved for detection of Alexa Fluor 488.

It is well established that within most of the engineering curriculum, social and environmental aspects of design and technology can be overlooked. Engineering design that lacks social and environmental considerations likely leads to instances where social injustices are perpetuated. To break down this systematic inadequate engineering education within our large public institution and to change the culture among our students, a team of four instructors and several undergraduate students have been working on educating undergraduate engineering students who are empowered and skilled enough to take head-on the global challenges that we are facing, with a heavy focus on changing courses in the curriculum to include more socially and environmentally conscious design and thinking. To achieve real change in all our undergraduate students, we introduced course modifications to required courses for civil and environmental engineers and mechanical engineers. We also have established a capstone follow-up course that aims to enroll students from several different departments, providing engineering students with an interdisciplinary design approach. There are two main thrusts which we plan to forward in this project – 1) introduction of environmentally and socially responsible concepts into the engineering curriculum through required courses; and 2) assessing several metrics that have been developed and implemented to track the student culture toward environmentally or socially responsible engineering. In this WIP paper, we will focus on the latter. The developed metrics will be utilized for pre and post-assessments of curricular changes and can be used to continuously track effectiveness. A survey instrument has been distributed to 1st year, 3rd year, and 4th year students every semester since Fall 2020. Though the team used the current survey literature to develop our survey questions, we tried to create questions that would measure how empowered students are to make important changes, not only how they feel, but if they have actually made active changes for the better. We also wanted to understand if the students’ engineering identity would shift after the introduction of the new content. So far, we have collected background quantitative and qualitative survey data, which will be discussed in this paper. Survey metrics are informative but are prompted and rely on self-assessment, which may bias toward positive responses. Additional novel metrics were implemented to measure student culture. Among these is a response to assignment prompts related to identifying characteristics of successful professional engineers. Initial results show high recognition of environmental and social responsibility when prompted, but room for improvement in terms of self-identifying these responsibilities as fundamental to the definition of professional engineering.

In this paper, we study integrated estimation and control of soft robots. A significant challenge in deploying closed loop controllers is reliable proprioception via integrated sensing in soft robots. Despite the considerable advances accomplished in fabrication, modelling, and model-based control of soft robots, integrated sensing and estimation is still in its infancy. To that end, this paper introduces a new method of estimating the degree of curvature of a soft robot using a stretchable sensing skin. The skin is a spray-coated piezoresistive sensing layer on a latex membrane. The mapping from the strain signal to the degree of curvature is estimated by using a recurrent neural network. We investigate uni-directional bending as well as bi-directional bending of a single-segment soft robot. Moreover, an adaptive controller is developed to track the degree of curvature of the soft robot in the presence of dynamic uncertainties. Subsequently, using the integrated soft sensing skin, we experimentally demonstrate successful curvature tracking control of the soft robot.

CMOS-based microelectronic sensors have great potential in the development of biosensors for medical and life science applications. Validating these lab-on-CMOS systems is a challenging task due to the difficulties in obtaining simultaneous ground-truth imaging and sensor data. In this work, we report a real-time imaging platform that generates high-quality images of lab-on-CMOS systems within cell culture environments. The platform was used to validate a CMOS capacitance sensor that monitors cell viability, proliferation, and death. In vitro experiments were performed with human ovarian cancer cell lines, in which time-lapse images and capacitance recordings were acquired simultaneously over three days. The images corroborate the temporal changes in capacitance recordings as the cells proliferate, and unambiguously confirm the sensor’s ability to detect single-cell binding events, track cell morphology changes, identify cell division events, and monitor cell motility.

We describe a capacitance sensor system-on-chip that has been incorporated into a lab-on-CMOS system for applications in monitoring cell viability. This paper presents system-level improvements to a capacitance sensor array that include programmable gain, active pixel settings, and serial bus addresses, while at the same time minimizing external bonding requirements towards developing a point-of-care device. Results from benchtop experiments are presented using dry flour to mimic for cell coverage, and show a change of up to 35 kHz. Estimation of electrode coverage is obtained using concurrent time-lapse imaging of the sensor surface which is then correlated to the sensor readings.

Integrating CMOS sensor chips to allow for wet experimentation on lab-on-CMOS devices is a challenging task. In this paper we describe a chip packaging method that will allow for simple integration and handling of small integrated circuit (IC) chips. A chip is embedded in an epoxy handle wafer to allow for photolithographic processing. Electrical connections are provided by a sputter-deposited copper layer and an electroplated nickel layer. Passivation was performed using a second epoxy layer. The process was evaluated by packaging a capacitance sensor chip and performing live cell culture experiments with package cleaning and reuse. Results showed good structural reliability in three repeated experiments over five cumulative days, with no adverse effects on the viability of cells.

We present performance characterization of a bio-potential recording system with an asynchronous readout architecture. The signal processing chain consists of a low-noise bio-potential amplifier, spike detection circuitry, and an address event representation (AER) communication protocol. The system was fabricated in a 0.5 pm CMOS technology. Each stage of the recording system was tested individually, and the systems' detection specificity and sensitivity were evaluated. For input spike amplitudes of 560 µV, a detection rate of 81 % was obtained with a false positive rate of 7 %.

Capacitance sensing is an emerging technology for monitoring cell viability. This work extends a previously developed sensor that measured capacitive loading by cells on the oscillation frequency of a current-starved ring oscillator and converted the frequency to a digital value by counting oscillation cycles. The new sensor array has been developed into a one-chip lab-on-CMOS system with integrated temperature sensors, serial readout to an external microcontroller using an Inter-Integrated Circuit (I2C) bus, and automatic scanning to allow for autonomous data collection. To allow sensing at the required aF levels, the system was realized on single chip to reduce the baseline capacitance, and long counting times were employed. The I2C module was moved to the edge of the chip prevent exposing cells to unacceptably high temperatures during viability studies.

Lab-on-CMOS chips (LOCMOS) are sophisticated miniaturized analysis tools based on integrated circuit (IC) microchips performing various laboratory functions. We have developed a low temperature co-fired ceramic (LTCC) package for a LOCMOS application regarding cytotoxicity assessment of nanomaterials. The LTCC packaged capacitance sensor chip is designed for long-term cell viability monitoring during nanoparticle exposure. The introduced LTCC package utilizes the flip chip bonding technique, and it is biocompatible as well as able to withstand the environmental conditions required to maintain mammalian cell culture directly on the surface of a complementary metal oxide semiconductor (CMOS) integrated circuit.

Co-robotics is interested in understanding how robots interact with other structures, such as humans, for the purpose of decision-making. Robots are currently designed to execute programmed actions to satisfy specific commands and motions. If a robot could be taught to perform an action by a guiding touch from a human, rather than specific programmed actions, a single learning approach could be broadly applied to multiple robotic platforms. In order for a robot to learn from touch, the robot must have a sense of touch. To provide the robot with this sense of touch, an artificial skin was created by applying a conductive exfoliated graphite/latex mixture to a compliant latex substrate, resulting in a highly compliant skin conformable to a variety of structures. The skin was designed with an array of strain gauges on both sides of the substrate to form a grid capable of detecting localized forces through changes in skin resistance. Model experiments were used to characterize the mechanics of these skins when placed over compliant substrates. Surface strain was characterized directly with 3D DIC, and shown to correspond quantitatively to changes in skin resistance. The ability of the skin to sense and be trained by touch has been demonstrated using a braille target and a commercial robot arm with a finger designed with the sensing skin. Using these skins, it will be possible for robots to feel and sense features of their environment through touch, and to be trained via touch.

We present an active micro-electrode array for neural recording with integrated spike detection and an asynchronous readout architecture. Neural amplifier arrays generate voluminous data because of the necessary per-channel sampling rates and number of channels in a dense array. Most of the time, neural cells produce well below 100 spikes per second, with action potential durations generally on the order of 1 ms, and accordingly much of the recorded data from a neural amplifier is not of interest. In the case of dense arrays recording from single units, only the timing of action potentials is relevant and spike sorting is not required. In such a case, the bandwidth requirement of the neural array can be reduced by employing an event-driven data communication protocol such as address event representation (AER). In our array, these events are generated by the spike detection circuits and then relayed to AER modules that send the address of the spiking neuron off-chip using a digital encoding scheme. Based on simulation data, the system implemented here reduces bandwidth requirements by a factor of 1600 in comparison to traditional synchronous sampling.

CMOS chips are increasingly used for direct sensing and interfacing with fluidic and biological systems. CMOS circuits for sample acquisition, signal processing, and readout have been integrated with various sensors to form complex biosystems-on-chip. However, distinct and vexing technical challenges arise from the disparate requirements of biosensors and integrated circuits. From the perspective of integrated circuits, direct CMOS biosensing creates challenges in: packaging; materials selection; physical design constraints due to topography; MEMS post-processing of CMOS die; energy and power limitations; and transfer and processing of signals. From the perspective of biology, direct CMOS biosensing creates challenges in: fluidic integration; electrochemical effects; biocompatibility; environmental maintenance and surface treatments to support cell health and function; and optical assessment of opaque samples. We will describe these challenges and review lessons learned.

In this investigation, we report on experiments and models we have developed for compliant multifunctional robotic structures using arrays of conducting polymer composites have been developed to form a “nervous system” to sense shape and force distributions. The objective of this research is to enable better training of robots by enabling them to physically communicate via human touch using new compliant multifunctional structures. To achieve this, arrays of conducting polymer composites have been developed to form a “nervous system” to sense shape and force distributions. This sensor array is integrated into compliant composite structures using a scalable additive manufacturing process. These sensor arrays are being developed for a variety of model robotic structures, for example flapping wing MAVs (i.e., bird-like robots) and stair-walking robots. Experimental details of the associated deformation response are quantified in real-time using Digital Image Correlation (DIC). Output from the sensor array is related to shape and force distributions by solving the nonlinear inverse problem using a novel Singular Value Decomposition (SVD) method. This research is leading to new compliant, scalable, sensing structures that simultaneously monitor in real-time both global and local shapes, as well as force distributions. Since compliant multifunctional sensing structures do not yet exist for robots, it is envisioned that it will enable realization of new bio-inspired control principles for training robots. This will significantly advance the ability to make safer interactions and decisions in co-robotics by differentiating robotic interactions with humans from other objects in their environment.

We have previously presented “nastic” actuators based on electroosmotic (EO) pumping of fluid in microchannels using high electric fields for potential application in soft robotics. In this work we address two challenges facing this technology: applying EO to meso-scale devices and the stability of the pumping fluid. The hydraulic pressure achieved by EO increases with as 1/d2, where d is the depth of the microchannel, but the flow rate (which determines the stroke and the speed) is proportional to nd, where n is the number of channels. Therefore to get high force and high stroke the device requires a large number of narrow channels, which is not readily achievable using standard microfabrication techniques. Furthermore, for soft robotics the structure must be soft. In this work we present a method of fabricating a three-dimensional porous elastomer to serve as the array of channels based on a sacrificial sugar scaffold. We demonstrate the concept by fabricating small pumps. The flexible devices were made from polydimethylsiloxane (PDMS) and comprise the 3D porous elastomer flanked on either side by reservoirs containing electrodes. The second issue addressed here involves the pumping fluid. Typically, water is used for EO, but water undergoes electrolysis even at low voltages. Since EO takes place at kV, these systems must be open to release the gases. We have recently reported that propylene carbonate (PC) is pumped at a comparable rate as water and is also stable for over 30 min at 8 kV. Here we show that PC is, however, degraded by moisture, so future EO systems must prevent water from reaching the PC.

Electroactive polymer (EAP) actuators should ideally have large stroke, high force, and reasonable speed. In this talk, we shall describe a hydraulic technology driven by electroosmostic fluid flow that should be able to achieve this performance [1]. Potential applications of these “nastic” actuators include soft robots, micropositioners, and camouflage skins. The bioinspiration for this work is the octopus, with its strong, dexterous tentacles and ability to squeeze through small openings. Electroosmotic flow occurs in micro- and nano-scale channels when a voltage is applied across the fluid. The walls of the channel have a surface charge, which leads to a build-up of oppositely-charged species in the solution. This latter mobile charge moves under the voltage, dragging the fluid in the microchannel with it. Electroosmosis has been used with aqueous solutions in capillary elecrophoresis and for fluid pumping in open systems. However, the high voltage required for pumping results in hydrolysis, and thus the generation of gas bubbles. Within a sealed actuator system, the gas results in loss of actuation pressure (because it is compressible) and device failure. We have demonstrated bubble-free pumping when using propylene carbonate (Figure 1). Performance characterization and new nastic devices will be presented.

Neural probe insertion methods have a direct impact on the longevity of the device in the brain. Initial tissue and vascular damage caused by the probe entering the brain triggers a chronic tissue response that is known to attenuate neural recordings and ultimately encapsulate the probes. Smaller devices have been found to evoke reduced inflammatory response. One way to record from undamaged neural networks may be to position the electrode sites away from the probe. To investigate this approach, we are developing probes with controllably movable electrode projections, which would move outside of the zone that is damaged by the insertion of the larger probe. The objective of this study was to test the capability of conjugated polymer bilayer actuators to actuate neural electrode projections from a probe shank into a transparent brain phantom. Parylene neural probe devices, having five electrode projections with actuating segments and with varying widths (50 - 250 µm) and lengths (200 - 1000 µm) were fabricated. The electroactive polymer polypyrrole (PPy) was used to bend or flatten the projections. The devices were inserted into the brain phantom using an electronic microdrive while simultaneously activating the actuators. Deflections were quantified based on video images. The electrode projections were successfully controlled to either remain flat or to actuate out-of-plane and into the brain phantom during insertion. The projection width had a significant effect on their ability to deflect within the phantom, with thinner probes deflecting but not the wider ones. Thus, small integrated conjugated polymer actuators may enable multiple neuro-experiments and applications not possible before.

Dielectric elastomer actuators (DEAs) consist of an elastomer sandwiched between two electrodes, and they undergo a large in-plane expansion upon the application of an electric field. They therefore require compliant electrodes that can stretch tens of percent. The most commonly used electrode material is carbon grease, which smears easily and is difficult to pattern. This paper outlines the fabrication and performance of a novel polydimethylsiloxane (PDMS) composite having a 15 wt% loading of exfoliated graphite (EG). This new material has a Young's modulus of only 0.9 MPa and a conductivity of 0.15 S/cm. Unlike other composite electrode materials, the Young's modulus of the PDMS/EG increases only slightly, by a factor of two, upon addition of the EG. Furthermore, the PDMS/EG composite is patternable and will not rub off. DEAs were fabricated with 20:1 PDMS as the elastomer using this new electrode material. The actuation strains were equal to those of 10:1 PDMS DEAs with carbon grease electrodes under the same electric field. Elastomer/EG composites may also find applications in areas such as flexible electronics, robotics, strain gauges, and sensors.

Most implantable chronic neural probes have fixed electrode sites on the shank of the probe. Neural probe shapes and insertion methods have been shown to have considerable effects on the resulting chronic reactive tissue response that encapsulates probes. We are developing probes with controllable articulated electrode projections, which are expected to provoke less reactive tissue response due to the projections being minimally sized, as well as to permit a degree of independence from the probe shank allowing the recording sites to "float" within the brain. The objective of this study was to predict and analyze the force-generating capability of conducting polymer bilayer actuators to actuate electrode projections from the probe shank under physiological settings. Custom parylene beams 1 cm long having varying widths (100 - 500 um) and thicknesses (8 - 15 um) were coated with Cr/Au. Polypyrrole was potentiostatically polymerized onto the Au at 0.5 V in a solution of 0.1 M pyrrole and 0.1 M dodecylbenzenesulfonate (DBS) to varying thicknesses. Using cyclic voltammetry, the bilayer beams were cycled between 0 and -1 V in artificial cerebral spinal fluid at 37 deg C, as well as in aqueous NaDBS at room temperature as a control. Video and scanning electron micrographs were taken and used to quantify thicknesses and deflections. Force and strain were measured. By integrating polypyrrole-based conducting polymer actuators, we present a novel microfabricated neural electrode. We demonstrate that by oxidizing and reducing the polymer layer, we can control electrode projection deflection under physiological settings.

Robotic structures are typically fabricated using discrete components that serve only a single function, such as carbon fibers or polymer composites for structural reinforcement. The ability to integrate these discrete components into a single structure provide enormous opportunities to enhance the performance of robots by reducing weight and increasing the energy storage/harvesting. We have recently been pursuing the integration of sensors and solar cells into multifunctional "skin" structures. One issue that limits the integration of these components is the effect that that the interaction between them will have on the mechanical behavior, and its subsequent impact on multifunctional performance. To minimize these effects and better understand the mechanics of multifunctional skin structures, we first pursued compliant strain sensors integrated onto compliant wings of a flapping wing MAV to sense deformations at the wing in real time. These measurements were correlated to the thrust force of the wing. The effects of these compliant strain sensors were also determined by comparing the new thrust measurements with the original wings and compared with 3D Digital Image Correlation (DIC) measurements. It was determined for SRS analysis that strain sensors tended to be more sensitive to lower integral modes of the flapping frequency than the thrust measurement data, while the DIC measurements correlated more directly with thrust measurements in the time domain. Thus, it would appear that the strain sensor and DIC measurements are sensitive to different aspects of the mechanics of the multifunctional skin structures that can be taken into account when using the strain sensors for real-time sensing and control. In addition to compliant strain sensor integration, flexible Solar Cells (SCs) were also integrated onto the compliant wings. Their ability to harvest energy during flight has the potential to prolong the time of flight for more autonomous operation. The effects of the integrated SCs on the 3D shapes of the compliant wings were also characterized during flapping. The solar cells had a significant effect on the wing shape, increasing the stiffness of the wings and reducing the volume of air that the wings need to capture to generate thrust, particularly at the apex and nadir of the flapping cycle where thrust is generated by blowback. Thus, a multifunctional analysis was developed to account for the tradeoff between the extra power require to generate the necessary thrust for the MAV to stay airborne versus what is gained from integrating the SCs in order to determine how to design the multifunctional skin structures to optimize performance.

Dielectric elastomer actuators (DEAs) consist of an elastomer sandwiched between two electrodes, and they undergo a large in-plane expansion upon the application of an electric field. They therefore require compliant electrodes that can stretch tens of percent. The most commonly used electrode material is carbon grease, which smears easily and is difficult to pattern. This paper outlines the fabrication and performance of a novel polydimethylsiloxane (PDMS) composite having a 15 wt% loading of exfoliated graphite (EG). This new material has a Young’s modulus of only 0.9 MPa and a conductivity of 0.15 S/cm. Unlike other composite electrode materials, the Young’s modulus of the PDMS/EG increases only slightly, by a factor of two, upon addition of the EG. Furthermore, the PDMS/EG composite is patternable and will not rub off. DEAs were fabricated with 20:1 PDMS as the elastomer using this new electrode material. The actuation strains were equal to those of 10:1 PDMS DEAs with carbon grease electrodes under the same electric field. Elastomer/EG composites may also find applications in areas such as flexible electronics, robotics, strain gauges, and sensors.

Dielectric elastomer actuators (DEAs) have been demonstrated for meso- and macro-scale applications, but only a few devices have been shown at the micro-scale, the most common of which have been diaphragms that bulge out of the plane of the wafer. Microscale DEAs would be of value in a wide range of small devices, including micro-robots, micro-pumps, and micro-optical systems. An additional advantage of miniaturizing is a reduction in the required driving voltage from kilovolts to tens of volts because the layers are thinner. However, fabrication of micro-scale DEAs remains challenging, due in part to the fact that the vast majority of macro-scale materials and/or fabrication methods cannot be adapted to the micro-scale. On the micro-scale, the elastomers must be deposited as thin films, they must be patternable, and they must be compatible with the other materials used during fabrication, such as sacrificial layers. The realization of compliant electrodes must also be handled in a new way. To fully realize the potential of micro-DEAs, it would also be desirable to develop fabrication procedures for integrating the micro-scale DEAS with complementary metal-oxide-semiconductor (CMOS) driver circuits and other micro-electro-mechanical systems (MEMS). This article addresses the progress that has been made thus far in making microfabricated DEAs, as well as the challenges and the key areas in which additional research needs to be pursued.

Although neural probe shapes and insertion methods have been shown to have considerable effects on the resulting chronic reactive tissue response that encapsulates probes, most implantable chronic neural probes have fixed electrode sites positioned on the shank of the probe. We are developing probes with controllable articulated electrode projections. Being minimally sized, they are expected to provoke less reactive tissue response, as well as to permit a degree of independence from the probe shank, allowing the recording sites to “float” within the brain. The objective of this study was to determine the force required to actuate parylene-based neural electrode projections in an agarose brain phantom. The agarose brain phantom has a similar mechanical viscosity as the brain, yet it is transparent allowing visualization of the inserted probes. Neural probes were fabricated with conducting polymer bilayer actuators to articulate the electrode projections. Electrode projections were designed to exert a range of forces by varying their widths and lengths, and the thickness of the conducting polymer, polypyrrole. Devices were inserted into the agarose brain phantom, and electrode projections were actuated. Digital images and video were analyzed to quantify the deflections. By integrating actuators on electrode projections, we anticipate having micron scale control of the final placement of electrode sites, resulting in longer-lasting, better-performing neural electrodes. This new functionality will hopefully allow us a new degree of freedom to explore and mitigate the reactive tissue response

Most implantable chronic neural probes have fixed electrode sites on the shank of the probe. Neural probe shapes and insertion methods have been shown to have considerable effects on the resulting chronic reactive tissue response that encapsulates probes. We are developing probes with controllable articulated electrode projections, which are expected to provoke less reactive tissue response due to the projections being minimally sized, as well as to permit a degree of independence from the probe shank allowing the recording sites to “float” within the brain. The objective of this study was to predict and analyze the force-generating capability of conducting polymer bilayer actuators to actuate electrode projections from the probe shank under physiological settings. Custom parylene beams 1 cm long having varying widths (100 – 500 um) and thicknesses (8 – 15 um) were coated with Cr/Au. Polypyrrole was potentiostatically polymerized onto the Au at 0.5 V in a solution of 0.1 M pyrrole and 0.1 M dodecylbenzenesulfonate (DBS) to varying thicknesses. Using cyclic voltammetry, the bilayer beams were cycled between 0 and -1 V in artificial cerebral spinal fluid at 37 deg C, as well as in aqueous NaDBS at room temperature as a control. Video and scanning electron micrographs were taken and used to quantify thicknesses and deflections. Force and strain were measured. By integrating polypyrrole-based conducting polymer actuators, we present a novel microfabricated neural electrode. We demonstrate that by oxidizing and reducing the polymer layer, we can control electrode projection deflection under physiological settings.

A new type of polymeric actuator has been developed based on a micro-scale hydraulic mechanism, in which electro-osmotic flow (EOF) is used to pump a fluid from one place to another in the device. This "nastic" actuator is in principle capable of producing both large displacements and high forces at reasonable speeds. Prototypes were fabricated from polydimethylsiloxane (PDMS) by micro-molding a fluid supply chamber, an expansion chamber, and connecting channels, and then topping this layer with a thin PDMS membrane. Upon applying a voltage across the two chambers, fluid flowed into the expansion reservoir, deflecting the membrane upward by hundreds of micrometers within a few seconds. The performance of these prototypes have been characterized in terms of deflection under load at various applied voltages, deflection vs. time upon input of a step potential, and repeatability. The performance of the actuator has been modeled, and the experimental and theoretical results are in reasonable agreement. The modeling work predicts that as the channel size is scaled down, the actuation stress will increase substantially, up to GPa for nano-channels, rivaling piezoelectrics and shape memory alloys but with much higher strain. Future applications of these actuators may include valves, shape-changing materials, and soft robotics.

We report on several techniques that have been pursued in our laboratories for packaging complementary metal oxide semiconductor (CMOS) sensors for use in biological environments, such as cell medium. These techniques are suited for single CMOS die ranging from 1.5 x 1.5 mm^2 to 3 x 3 mm^2 in area. The first method consisted of creating high aspect ratio structures from negative-tone photocurable resins to simultaneously encapsulate wirebonds from the chip to a ceramic package and create a cell culture well. The second technique used a photolithographically defined barrier on the die to allow the use of non-photocurable resins as encapsulants. The third method consisted of re-routing the die padframe using photolithographically defined, planar leads to a much larger padframe; this will allow the chip to be integrated with microfluidic networks. Finally, we show a method in which the encapsulant was also used as an optical filter and as a base for integrating more complex structures.

Cell-based sensors are being developed to harness the specificity and sensitivity of biological systems for sensing applications, from odor detection to pathogen classification. These integrated systems consist of CMOS chips containing sensors and circuitry onto which microstructures have been fabricated to transport, contain, and nurture the cells. The structures for confining the cells are micro-vials that can be opened and closed using polypyrrole bilayer actuators. The system integration issues and advances involved in the fabrication and operation of the actuators are described.

In this work we present the loading of cells into SU8 cages using dielectrophoresis (DEP). Simply attracting cells into the cages using positive DEP is impossible because of parasitic traps that are a result of electric field distortions produced by the cage. By implementing multiple frequencies on multiple electrodes simultaneously, one can cancel the parasitic traps. Using this technique, areas on the substrate in which dielectrophoresis takes place may now include features that would otherwise interfere with the manipulations. Numerical and experimental results are presented.

The ions present in the electrolyte in which a conjugated polymer actuator is cycled are known to affect performance. Understanding how force, response time, and strain are affected by ion size and other ion characteristics is critical to applications, but is not yet well understood. In this paper, we present the effect of alkali cation size on transport velocity and volume change in polypyrrole doped with dodecylbenzenesulfonate, PPy(DBS), which is a cation-transporting material. Volume change measured by mechanical profilometry is greatest for Li+ and decreases in order of atomic mass: Li+ > Na+ > K+ > Rb+ > Cs+. Ion transport, measured by phase front propagation experiments, is also fastest for Li+, contradicting the expectation that larger species would move more slowly.

Previously, we presented a model for ion transport in conjugated polymers during electrochemical reduction. In this paper, we will present a more advanced model that includes hole transport, which was neglected in the first-cut model. This addition takes into account the interactions between holes and cations during transport. The result is that the front between oxidized and reduced material now propagates with constant velocity, instead of slowing down over time. Also, an electrolyte layer has been added to the model, and as a result the ion concentration behind the phase front is more accurately predicted.

It is important to increase the switching speed of conjugated polymers between oxidized and reduced states for a wide range of devices, including capacitors, electrochromic displays, and actuators. In this paper, we compare the in-plane and the out-of-plane ion transport speed during electrochemical reduction of a conjugated polymer, polypyrrole doped with dodecylbenzenesulfonate. Results show that the in-plane ion transport is approximately 50 times faster than out-of-plane transport. The anisotropy is likely induced by the dodecylbenzenesulfonate, which has been shown previously to form layers parallel to the surface. An engineering method is presented to enhance the in-plane ion transport by etching pores into the polymer.

We present the concept of a MEMS kit with associated lesson plans that can be used to give students hands-on fabrication experience that is analogous to what is done in a clean room, but on a larger scale so that no expensive equipment is needed.

We describe a potentiostat designed for in situ control of MEMS actuators. This module will be integrated into cell clinics, a hybrid CMOS-MEMS biolab system-on-a-chip to confine and measure signals from individual cells. We briefly review the current status of cell clinics as it pertains to this effort. We specify the requirements of a potentiostat for this application and describe a design satisfying these requirements. The design has been fabricated in a commercially available 0.5 mm CMOS process. The fabricated chip has been successfully employed for the control of electroactive polymer films and actuators used in cell clinics.

A compliant electrode material is presented that was inspired by the electroding process used to manufacture ionic polymer-metal composites (IPMCs). However, instead of an ion-exchange membrane, a UV-curable acrylated urethane elastomer is employed. The electrode material consists of the UV-curable elastomer (Loctite 3108) loaded with tetraammineplatinum(II) chloride salt particles through physical mixing and homogenization. The composite material is made conductive by immersion in a reducing agent, sodium borohydride, which reduces the salt to platinum metal on the surface of the elastomer film. Because the noble metal is mixed into the elastomer precursor as a salt, the amount of UV light absorbed by the precursor is not significantly reduced, and the composite loses little photopatternability. As a result meso-scale electrodes of varying geometries can be formed by exposing the precursor/salt mixture through a mask. The materials are mechanically and electrically characterized. The percolation threshold of the composite is estimated to be 9 vol. % platinum salt, above which the compliant electrode material exhibits a maximum conductivity of 1 S/cm. The composite maintains its electrical conductivity under axial tensile strains of up to 40%.

Bilayer microactuators of gold and polypyrrole doped with dodecylbenzene sulfonate, PPy(DBS), are characterized with respect to their response times and the influence of operation temperature. These parameters are needed for biomedical applications such as microvalves. To fully open and close the valves, the bilayer hinges must be able to rotate within a few seconds at body temperature. Bilayers were subjected to potential steps to switch the PPy between the oxidized and reduced states. Actuation was viewed through an optical microscope and recorded by a digital camera. The velocity profiles during reduction and oxidation follow the same trends. Two different phases of actuation can be identified. In the first phase there is rapid movement, and in the second phase the velocities slowly decrease until the position reaches steady-state. In order to investigate the effects of elevated temperature on the actuators, the operation temperature was varied stepwise from 25 °C to 55 °C. The curvature increased irreversibly by up to 45% at elevated temperatures, and the output force dropped.

We report on a custom designed system for the deposition and characterization of polypyrrole bilayer actuators. Unlike conventional commercial electrochemical cells and potentiostats, the system described in this paper has specications commensurate to its application and thus can be readily implemented using off the shelf electronic components at relatively low cost. Deposition rates and actuation are computer controlled through a standard data acquisition interface card with a program written in Matlab. We also discuss the design of the masks that are employed to fabricate the polypyrrole structures. This is accomplished through silicon compilation using the CAD software LEDIT [1] from Tanner Research. We have implemented a selection of parameterized routines in the LEDIT script language LComp that greatly reduces design turnaround time.

The transport of charged species, including both polarons/bipolarons and charge-compensating ions, occurs when conjugated polymers switch between oxidized and reduced states. However, physics-based models of the charge transport processes have not yet been developed. Previously, we presented an electrochromic device that made the path for ion transport much longer than that for electrons, ensuring that ion transport was the rate-limiting step so that the constitutive equation for ion transport could be formulated. Ion concentration profiles and velocities could be tracked by color changes. In this paper, we present the correlation between ion transport and volume change, measured in this device using a mechanical profilometer to scan height profiles during electrochemical reduction. In addition, the effects of electrolyte concentration, electrolyte temperature, film thickness, and ion barrier stiffness on ion transport velocities are explored.

We present the use of electroactive polymer actuators as components of a biolab-on-a-chip, which has potential applications in cell-based sensing.

We describe a CMOS capacitance sensor for measuring the capacitive coupling between living cells and the underlying substrate, a quantity that can be used to characterize cell adhesion strength and cell health. The capacitance sensor operates on the charge sharing principle, mapping sensed capacitance values to voltages. The sensor has been fabricated in a commercially available 0.5 mm, 2-poly 3-metal CMOS technology. Experimental results are presented for bench tests using a micropositioned electrode and in vitro tests with cells cultured directly on the chip surface. The sensor achieves an empirical distance resolution of 3 nm and capacitance resolution of 135 aF. The sensors have been successfully used for long term monitoring of cell viability in vitro.

Improving the lifetime of conjugated polymer-based devices that undergo repeated cyclic electrical stimulation, such as actuators, is important for commercialization.

Certain electroactive polymer actuators produce mechanical strains in excess of 1% under the application of a voltage. These actuator materials include conducting polymers, ionomeric polymers or IPMCs, carbon nanotube and polymernanotube composites, ferroelectric polymers and dielectric elastomer materials. The ability to generate mechanical strain in excess of 1% under voltage application differentiates electroactive polymers from other types of active materials, such as piezoelectric polymers and ceramics, which are generally limited to strains less than 1%. To date there has been no development of standardized testing methods for this class of electroactive materials. The development of standardized testing methods would create consistent metrics on which to compare actuator materials. In this work we present a set of standard testing methods for two classes of electroactive polymer actuators. Extensional actuators are defined as materials whose dominant response is expansion or contraction upon application of an electric field. Bender actuators are defined as those whose dominant response is a bending deflection upon the application of a voltage. The standardized testing method for each of these actuators contains detailed schematics of test fixtures for testing of mechanical, electrical, and electromechanical properties. The test method for each actuator type specifies the environmental conditions that must be controlled and reported for each test condition. Furthermore, methods of obtaining data and processing the results are discussed to create a consistent database of material properties and actuator performance metrics. The key properties tested in this method are the stress and strain induced by the applied voltage, material properties, and properties associated with the polymer composition. In addition, we propose the development of a standardized nomenclature and parameter definition that will facilitate analysis of published data and allow direct comparison of data between various research groups and materials developers.

There is a growing interest in developing low cost, low power, highly integrated biosensor systems to characterize individual cells for applications such as cell analysis, drug development, environmental monitoring, and medicine. In such micro-systems, it’s desirable to track individual cells in real time in order to steer cells using on-chip micro-actuators or monitor the movement of motile cells. To address this requirement, we are developing an embedded optical image sensor, called a contact imager, for imaging of a biological specimen directly coupled to the chip surface. The designed CMOS image sensor comprises an array of active pixel sensors (APS), logic and control signal generation, and readout circuits. The pixel layout has a pitch of 8.4 mm. The design was fabricated in a commercially available 0.5 ìm CMOS technology. The imager was first characterized on the bench as a normal CMOS image sensor, and then as a contact imager with microbeads (16 mm) placed directly on the chip surface. After further packaging with bio-compatible material, the chip was tested with cells cultured directly on the chip surface. Test results confirm successful detection of both beads and cells.

Polypyrrole/gold bilayer microactuators are being developed in our laboratory for biomedical applications such as microvalves. To fully open and close the valves, the bilayer hinges must be able to rotate between 0° and 180° within a few seconds against external forces. The layer thicknesses and hinge lengths must therefore be properly designed for the application. However, existing models fail to predict the correct behavior of microfabricated PPy/Au bilayer microactuators. Therefore, additional experimental data are needed to correctly forecast their performance. Bilayer actuators were fabricated with ranges of PPy thicknesses and hinge lengths. Bending angles were recorded through a stereomicroscope in the fully oxidized and reduced states. Isometric forces exerted by the hinges were measured with a force transducer, the output of which was read by a potentiostat and correlated with the applied potentials.

We describe a bioMEMS system for confining and electrically interfacing to single cells for long-term studies. The system comprises microvials that can be covered and uncovered by lids actuated by polypyrrole/gold hinges. Within each vial are integrated bio-amplifiers and/or other sensing circuits to form a biolab-on-a-chip. We have developed a process sequence for fabricating lidded microvials with actuated lids on CMOS die. Initial testing of these “cell clinics” with bovine aortic smooth muscle cells yields successful sensing of the extracellular action potentials from bovine aortic smooth muscle cells using a custom VLSI bioamplifier.

In this paper, we present a biolab-on-a-chip that integrates microstructures for capturing and culturing living cells together with electronics for in-situ measurement and characterization. The microsystem is composed of an array of cell-holding vials (150 x150x10 mm3, LxWxH) on a custom IC chip (1.5x1.5 mm2) fabricated in a commercially available 1.5 mm CMOS technology. In order to encage the cells, each vial is opened and closed by a lid (Figure 2) that is rotated by a polypyrrole/gold bilayer hinge. The hinges require only 1 V for actuation, which is compatible with the CMOS circuitry and with the cells. Inside each vial, an electrode connected to a VLSI bio-amplifier circuit will acquire electrical measurements on the cells, which are electrically isolated from the aqueous medium and other cells when the lids are closed.

We have developed a method to fabricate substrates that can fold themselves. The microstructures are actuated by an electroactive polymer, polypyrrole (PPy). A series of bilayers is defined on one surface of the substrate, and hinges are formed by etching the substrate from the back side to undercut the bilayers. A shape-morphing object is demonstrated that comprises multiple hinges. This object was able to bend both forward and backward. We are applying this technology to fabricate medical devices that operate in bio-fluids.

In this work, we investigated the electrochem. actuation of gilded polyaniline bilayers in acidic aqueous electrolytes. Gilding was found to be a useful method to ensure a uniform potential distribution across polyaniline films so that well-defined electrochemistry and electrochemical actuation could be obtained. Electrochemical actuation of gilded polyaniline bilayers was studied by means of bending and linear actuation. Actuation could be obtained by a number of electrochemical stimulation modes, including cyclic voltammetry (CV), square wave potential (SWP), and square wave current (SWC). Within the potential range of -0.2 to 0.6 V (vs Ag/AgCl), the polyaniline films expanded upon oxidn. and contracted upon reduction, which corresponds to the first redox process of polyaniline between the leucomeraldine and emaraldine oxidn. states. Actuation obtained in this potential range is related to the insertion/deinsertion of the electrolyte anion upon oxidation/reduction of polyaniline. It was found that, due to the thin thickness of the gold layer, not only fast bending actuation but also linear actuation could be achieved for the resulting gilded polyaniline bilayers. Extending the applied potential to more positive potentials, polyaniline degradation and oxidation of gold layer were observed.

The volume change that the conducting polymer polypyrrole (PPy) undergoes upon electrochem. oxidn. and redn. can be used to make microactuators. The authors have made microactuators based on a PPy/Au bilayer. These actuators have been combined with other micromachined structures to make biomedical microdevices. By using an area of bilayers, one can potentially arrest (nerve) fibers. They can also be used to close a micrometer-sized cavity with a lid. In addition, the authors demonstrate a microrobotic arm that may be developed for the manipulation of small particles.

We present the results of a study of the effect of photolithographed gratings on glass and silicon wafers on the alignment of smectic liq. crystal mols. The gratings have periods in the range of 200 nm -200 mm, and depths of up to 2 mm. We found that smectic liq. crystals align sharply along the gratings, depending on the temp. cycling method used in loading the roughness obsd. in glass gratings. The quality of the alignment is uniform in the range 664 nm-24 mm, and breaks down outside this region, setting lower and upper boundaries for gating prepn.

The results of structural measurements on smectic liquid crystal films deposited on photolithographed gratings on both glass and Si substrates are presented. These gratings have periods in the range of 664 nm-200 mm, and depths of up to 2 mm. Both Si and glass gratings are able to align the liquid crystal in the period range 664 nm -24 mm, as determined using both x-ray diffraction and optical microscopy. This result sets upper and lower boundaries for grating preparation. The results of the measurements were fit to a multilayer orientational model to determine the thickness of the observed aligned layer. The possible impact of the results on large area display packaging and preparation are discussed.

The strain field was examined in the film as a function of annealing time. The technique chosen was grazing incidence x-ray scattering. The BaTiO3 {110} and {101} reflections were monitored. A substantial relaxation of the d-spacing of planes parallel to the surface was measured after a 64 h annealing. The d-spacing of planes perpendicular to the surface remained essentially unchanged.

An optical sensor sensitive to changes in light absorption and other optical interactions, and consisting of 2 fibers twisted around each other, is described. The sensor can be used as a refractometer, is sensitive to the presence of H2O in oil, can be used to determine the amount of a solvent in oil, and might be useful in monitoring degradation of internal combustion engine oil. In addition, by surrounding the fibers with a film of solution, and observing the changes in output over time, additional information can be obtained. Used in this manner, the sensor can be used to identify specific solutions.