Berkeley Sensor and Actuator Center

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Berkeley Sensor and Actuator Center

United States

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News Article | January 28, 2016
Site: www.cemag.us

When UC Berkeley engineers say they are going to make you sweat, it is all in the name of science. Specifically, it is for a flexible sensor system that can measure metabolites and electrolytes in sweat, calibrate the data based upon skin temperature, and sync the results in real time to a smartphone. While health monitors have exploded onto the consumer electronics scene over the past decade, researchers say this device, reported in the journal Nature, is the first fully integrated electronic system that can provide continuous, non-invasive monitoring of multiple biochemicals in sweat. The advance opens doors to wearable devices that alert users to health problems such as fatigue, dehydration and dangerously high body temperatures. “Human sweat contains physiologically rich information, thus making it an attractive body fluid for non-invasive wearable sensors,” says study principal investigator Ali Javey, a UC Berkeley professor of electrical engineering and computer sciences. “However, sweat is complex and it is necessary to measure multiple targets to extract meaningful information about your state of health. In this regard, we have developed a fully integrated system that simultaneously and selectively measures multiple sweat analytes, and wirelessly transmits the processed data to a smartphone. Our work presents a technology platform for sweat-based health monitors.” Javey worked with study co-lead authors Wei Gao and Sam Emaminejad, both of whom are postdoctoral fellows in his lab. Emaminejad also has a joint appointment at the Stanford School of Medicine, and all three have affiliations with the Berkeley Sensor and Actuator Center and the Materials Sciences Division at Lawrence Berkeley National Laboratory. To help design the sweat sensor system, Javey and his team consulted exercise physiologist George Brooks, a UC Berkeley professor of integrative biology. Brooks said he was impressed when Javey and his team first approached him about the sensor. “Having a wearable sweat sensor is really incredible because the metabolites and electrolytes measured by the Javey device are vitally important for the health and well-being of an individual,” says Brooks, a co-author on the study. “When studying the effects of exercise on human physiology, we typically take blood samples. With this non-invasive technology, someday it may be possible to know what’s going on physiologically without needle sticks or attaching little, disposable cups on you.” The prototype developed by Javey and his research team packs five sensors onto a flexible circuit board. The sensors measure the metabolites glucose and lactate, the electrolytes sodium and potassium, and skin temperature. “The integrated system allows us to use the measured skin temperature to calibrate and adjust the readings of other sensors in real time,” says Gao. “This is important because the response of glucose and lactate sensors can be greatly influenced by temperature.” Adjacent to the sensor array is the wireless printed circuit board with off-the-shelf silicon components. The researchers used more than 10 integrated circuit chips responsible for taking the measurements from the sensors, amplifying the signals, adjusting for temperature changes and wirelessly transmitting the data. The researchers developed an app to sync the data from the sensors to mobile phones, and fitted the device onto “smart” wristbands and headbands. They put the device — and dozens of volunteers — through various indoor and outdoor exercises. Study subjects cycled on stationary bikes or ran outdoors on tracks and trails from a few minutes to more than an hour. “We can easily shrink this device by integrating all the circuit functionalities into a single chip,” says Emaminejad. “The number of biochemicals we target can also be ramped up so we can measure a lot of things at once. That makes large-scale clinical studies possible, which will help us better understand athletic performance and physiological responses to exercise.” Javey notes that a long-term goal would be to use this device for population-level studies for medical applications. Brooks also notes the potential for the device to be used to measure more than perspiration. “While Professor Javey’s wearable, non-invasive technology works well on sweating athletes, there are likely to be many other applications of the technology for measuring vital metabolite and electrolyte levels of healthy persons in daily life,” says Brooks. “It can also be adapted to monitor other body fluids for those suffering from illness and injury.” The Berkeley Sensor and Actuator Center and the National Institutes of Health helped support this work.


Ford A.C.,University of California at Berkeley | Ford A.C.,Berkeley Sensor and Actuator Center | Ford A.C.,Lawrence Berkeley National Laboratory | Yeung C.W.,University of California at Berkeley | And 14 more authors.
Applied Physics Letters | Year: 2011

An ultrathin body InAs tunneling field-effect transistor on Si substrate is demonstrated by using an epitaxial layer transfer technique. A postgrowth, zinc surface doping approach is used for the formation of a p+ source contact which minimizes lattice damage to the ultrathin body InAs compared to ion implantation. The transistor exhibits gated negative differential resistance behavior under forward bias, confirming the tunneling operation of the device. In this device architecture, the ON current is dominated by vertical band-to-band tunneling and is thereby less sensitive to the junction abruptness. The work presents a device and materials platform for exploring III-V tunnel transistors. © 2011 American Institute of Physics.


So H.,Berkeley Sensor and Actuator Center | Lee K.,University of California at Berkeley | Seo Y.H.,Kangwon National University | Murthy N.,University of California at Berkeley | Pisano A.P.,Berkeley Sensor and Actuator Center
ACS Applied Materials and Interfaces | Year: 2014

This letter reports an efficient and compatible silicon membrane combining the physical properties of nanospikes and microchannel arrays for mechanical cell lysis. This hierarchical silicon nanospikes membrane was created to mechanically disrupt cells for a rapid process with high throughput, and it can be assembled with commercial syringe filter holders. The membrane was fabricated by photoelectrochemical overetching to form ultrasharp nanospikes in situ along the edges of the microchannel arrays. The intracellular protein and nucleic acid concentrations obtained using the proposed membrane within a short period of time were quantitatively higher than those obtained by routine, conventional acoustic and chemical lysis methods. © 2014 American Chemical Society.


Choi S.,Berkeley Sensor and Actuator Center | Pisano A.P.,Berkeley Sensor and Actuator Center
Materials Research Society Symposium Proceedings | Year: 2011

We report simple and effective methods to develop long-term, stable silicon nanowire-based pH sensors and systematic studies of the performance of the developed sensors. In this work, we fabricate silicon nanowire pH sensors based on top-down fabrication processes such as E-beam lithography and conventional photolithography, In order to improve the stability of the sensor performance, the sensors are coated with a passivation layer (silicon nitride) for effective electrical insulation and ion-blocking. The stability, the pH sensitivity, and the repeatability of the sensor response are critically analyzed with regard to the physics of sensing interface between sample liquid and the sensing surface. The studies verify that the sensor with a passivation layer over critical thickness show long-term, stable sensor response without long-term drift. The studies also show the detection of pH level with silicon nanowire sensors is repeatable only after proper rinsing of sensor surfaces and there exists trade-off between the stability and the pH sensitivity of sensor response. © 2011 Materials Research Society.


Choi S.,Berkeley Sensor and Actuator Center | Pisano A.P.,Berkeley Sensor and Actuator Center
14th International Conference on Miniaturized Systems for Chemistry and Life Sciences 2010, MicroTAS 2010 | Year: 2010

We report simple and effective methods to develop long-term, stable silicon nanowire-based pH sensors and systematic studies of the performance of the developed sensors. In this work, we fabricate silicon nanowire pH sensors based on top-down fabrication processes such as E-beam lithography and conventional photolithography. In order to improve the stability of the sensor performance, the sensors are coated with a passivation layer (silicon nitride) for effective electrical insulation and ion-blocking. The stability, the pH sensitivity, and the repeatability of the sensor response are critically analyzed with regard to the physics of sensing interface between sample liquid and the sensing surface. The studies verify that the sensor with a passivation layer over critical thickness show long-term, stable sensor response without long-term drift. The studies also show the detection of pH level with silicon nanowire sensors is repeatable only after proper rinsing of sensor surfaces and there exists trade-off between the stability and the pH sensitivity of sensor response.


Wu A.,Berkeley Sensor and Actuator Center | Wu A.,University of California at Berkeley | Wang L.,Berkeley Sensor and Actuator Center | Wang L.,University of California at Berkeley | And 4 more authors.
Lab on a Chip - Miniaturisation for Chemistry and Biology | Year: 2010

Microfluidic systems offer an attractive alternative to conventional wet chemical methods with benefits including reduced sample and reagent volumes, shorter reaction times, high-throughput, automation, and low cost. However, most present microfluidic systems rely on external means to analyze reaction products. This substantially adds to the size, complexity, and cost of the overall system. Electronic detection based on sub-millimetre size integrated circuits (ICs) has been demonstrated for a wide range of targets including nucleic and amino acids, but deployment of this technology to date has been limited due to the lack of a flexible process to integrate these chips within microfluidic devices. This paper presents a modular and inexpensive process to integrate ICs with microfluidic systems based on standard printed circuit board (PCB) technology to assemble the independently designed microfluidic and electronic components. The integrated system can accommodate multiple chips of different sizes bonded to glass or PDMS microfluidic systems. Since IC chips and flex PCB manufacturing and assembly are industry standards with low cost, the integrated system is economical for both laboratory and point-of-care settings. © 2010 The Royal Society of Chemistry.


Liu Y.,Berkeley Sensor and Actuator Center | Lin S.,University of California at Berkeley | Lin L.,University of California at Berkeley
2015 Transducers - 2015 18th International Conference on Solid-State Sensors, Actuators and Microsystems, TRANSDUCERS 2015 | Year: 2015

This work reports the technique to selectively sense different gases using a single graphene field effect transistor (FET) by measuring real time conductance as a function of gate voltage. Compare to the state-of-art, three distinctive advancements have been achieved: (1) first demonstration of selective gas sensing (NO2, NH3, H2O and CH3OH) using a single graphene FET; (2) experimental proof of linear dependence between the reciprocal of carrier mobility limited by long-range scattering and the Dirac Point voltage upon gas molecule exposure; (3) utilizations of such linear characteristic for selective gas sensing. As such, the proposed sensing scheme and results could open up a new class of graphene-based, selective gas sensing devices for practical uses as well as fundamental scientific research. © 2015 IEEE.


Liu F.,Berkeley Sensor and Actuator Center | Liu F.,University of California at Berkeley | Hsia B.,University of California at Berkeley | Carraro C.,Berkeley Sensor and Actuator Center | And 5 more authors.
Applied Physics Letters | Year: 2010

Electrical contact to silicon carbide with low contact resistivity and high stability is a critical requirement for SiC-based microsystem and nanosystem technology for harsh environment applications. In this letter, nanocrystalline graphitic carbon is grown at the interface between SiC and Pt to lower the Ohmic contact resistivity and enhance the stability of Pt contacts to polycrystalline 3C-SiC operated at elevated temperatures. Analysis shows that reduced barrier height, oxide-free surface, reduced density of vacancy defects, and suppressed reactivity between Pt and SiC are likely responsible for the reduced Ohmic contact resistivity and high thermal stability of Pt contacts to graphitized SiC. © 2010 American Institute of Physics.


Kapadia R.,University of California at Berkeley | Kapadia R.,Berkeley Sensor and Actuator Center | Fan Z.,University of California at Berkeley | Fan Z.,Berkeley Sensor and Actuator Center | And 2 more authors.
Applied Physics Letters | Year: 2010

The performance dependence of a CdS/CdTe nanopillar solar cell on various device and materials parameters is explored while examining its performance limits through detailed device modeling. The optimized cell enables efficiencies >∼20% with minimal short circuit current dependence on bulk minority carrier diffusion length, demonstrating the efficient collection of photogenerated carriers, therefore, lowering the materials quality and purity constraints. Given the large p-n junction interface area, the interface recombination velocity is shown to have detrimental effect on the device performance of nanopillar solar cells. In that regard, the CdS/CdTe material system is optimal due to its low interface recombination velocity. © 2010 American Institute of Physics.


Specifically, it is for a flexible sensor system that can measure metabolites and electrolytes in sweat, calibrate the data based upon skin temperature and sync the results in real time to a smartphone. While health monitors have exploded onto the consumer electronics scene over the past decade, researchers say this device, reported in the Jan. 28 issue of the journal Nature, is the first fully integrated electronic system that can provide continuous, non-invasive monitoring of multiple biochemicals in sweat. The advance opens doors to wearable devices that alert users to health problems such as fatigue, dehydration and dangerously high body temperatures. "Human sweat contains physiologically rich information, thus making it an attractive body fluid for non-invasive wearable sensors," said study principal investigator Ali Javey, a UC Berkeley professor of electrical engineering and computer sciences. "However, sweat is complex and it is necessary to measure multiple targets to extract meaningful information about your state of health. In this regard, we have developed a fully integrated system that simultaneously and selectively measures multiple sweat analytes, and wirelessly transmits the processed data to a smartphone. Our work presents a technology platform for sweat-based health monitors." Javey worked with study co-lead authors Wei Gao and Sam Emaminejad, both of whom are postdoctoral fellows in his lab. Emaminejad also has a joint appointment at the Stanford School of Medicine, and all three have affiliations with the Berkeley Sensor and Actuator Center and the Materials Sciences Division at Lawrence Berkeley National Laboratory. To help design the sweat sensor system, Javey and his team consulted exercise physiologist George Brooks, a UC Berkeley professor of integrative biology. Brooks said he was impressed when Javey and his team first approached him about the sensor. "Having a wearable sweat sensor is really incredible because the metabolites and electrolytes measured by the Javey device are vitally important for the health and well-being of an individual," said Brooks, a co-author on the study. "When studying the effects of exercise on human physiology, we typically take blood samples. With this non-invasive technology, someday it may be possible to know what's going on physiologically without needle sticks or attaching little, disposable cups on you." The prototype developed by Javey and his research team packs five sensors onto a flexible circuit board. The sensors measure the metabolites glucose and lactate, the electrolytes sodium and potassium, and skin temperature. "The integrated system allows us to use the measured skin temperature to calibrate and adjust the readings of other sensors in real time," said Gao. "This is important because the response of glucose and lactate sensors can be greatly influenced by temperature." Adjacent to the sensor array is the wireless printed circuit board with off-the-shelf silicon components. The researchers used more than 10 integrated circuit chips responsible for taking the measurements from the sensors, amplifying the signals, adjusting for temperature changes and wirelessly transmitting the data. The researchers developed an app to sync the data from the sensors to mobile phones, and fitted the device onto "smart" wristbands and headbands. They put the device - and dozens of volunteers - through various indoor and outdoor exercises. Study subjects cycled on stationary bikes or ran outdoors on tracks and trails from a few minutes to more than an hour. "We can easily shrink this device by integrating all the circuit functionalities into a single chip," said Emaminejad. "The number of biochemicals we target can also be ramped up so we can measure a lot of things at once. That makes large-scale clinical studies possible, which will help us better understand athletic performance and physiological responses to exercise." Javey noted that a long-term goal would be to use this device for population-level studies for medical applications. Brooks also noted the potential for the device to be used to measure more than perspiration. "While Professor Javey's wearable, non-invasive technology works well on sweating athletes, there are likely to be many other applications of the technology for measuring vital metabolite and electrolyte levels of healthy persons in daily life," said Brooks. "It can also be adapted to monitor other body fluids for those suffering from illness and injury." Explore further: Paper-thin e-skin responds to touch by lighting up

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